Mercury continues the tradition of the company that pioneered audio transformers in the U.K. Perhaps best known for their role in vintage Hiwatt amps, Partridge remains amongst the most preferred transformers from British amps of that era. Their design and build quality was a rarity, even for back then. And, like all well-made transformers from great designs, the original Partridges have their own outstanding tonal and other sonic qualities.
Our Partridge line are clones of the original Partridge transformers used mostly in the first Hiwatt amps. All Partridge transformers come with both our 10-year Workmanship Warranty and Tonal Guarantee.
Partridge transformers may be used for upgrades, replacements or custom tube-based guitar amp applications.
To find out more, or discuss to discuss the characteristics of the different tranny sets available for your amps, give us a call or email.
Partridge TG9685 — 120V, 220V, 230V & 240V primary — Partridge transformer design
3 Henry
20 Henry
’70s 200 watt — model DR-201 — Partridge transformer design
#TG 9424 — vertical mount, bolt hole spacing is 3 1/2″ x 3 1/2″
’70s 200 watt — model DR-201 — Partridge transformer design
#TG 7239 — vertical mount, bolt hole spacing is 3 1/2″ x 3″
4, 8 & 16 Ohm taps — 100V secondary tap — Partridge transformer design. Uses Grain-Oriented Iron
It doesn’t take too much digging to find a laundry list of boutique amp builders using Mercury Magnetics transformers in their products. From Mojave Ampworks to Joe Morgan Amps to kits from MetroAmp, builders have found that Mercury knows their iron. While transformers rarely receive the same level of attention of NOS tubes, speakers, or even guitar cables, they are a major contributor to tone. Think about it—the power and output transformers are the start and end of the line with any amp.
Based in Chatsworth, California, Mercury Magnetics has been building transformers for close to 60 years. I recently had a chance to talk with Mercury’s Sergio Hamernik to dig deeper into their roots, find out what one can expect from upgrading their iron, and what sets Mercury apart. Prior to our conversation, I had the opportunity to witness the remarkable transformation of an Epiphone Valve Junior modified from stock to hot-rodded, using one of their transformer upgrade kits. Not only was it a noticeable upgrade, it was a revelation in just how important the role of quality iron in an amp is. But because it is the single most expensive part of any amp, it’s no wonder we see so many modern amp manufacturers skimp on the iron to keep costs down. Let’s see what the passionate, and often hilarious, Sergio has to say about his part of the business.
PG: I’ve been seeing Mercury transformers in amps for at least a decade. When did you get into the amp scene?
SH: This happens to be one of our most often asked questions. Even though Mercury Magnetics’ roots go all the way back to the early 1950s, there are guitar players who are only now discovering us. But if an industry insider like you has been aware of us for at least a decade, then I suppose it means I don’t need to lay off any of our sales and marketing staff.
I would attribute most of our lingering anonymity to the old days. Back then, most of our clients from the audio community preferred to keep us as a trade secret from their competitors and the press. The typical transformer-savvy amp builder also didn’t usually want to share the credit with us, or reveal what their “unique” technical advantage was regarding audio and tone. Consequently, we were asked to maintain a low profile and generic look for our transformers for quite some time. On occasion, a customer in the know will spot a small “MM” mark on a transformer from an older piece of gear, and ask if it’s a Mercury. Odds are that it is.
It was the guitar amp crowd that pushed us to go above ground. Now Mercury gives any electric guitar player or amp restorer a taste of what the pros were using, talking about in their studios, and among themselves. Many players have told us their amps increased in value when upgraded with Mercury transformers, and this became evident when insurance appraisers began to contact us for verification. However, it wasn’t until the mid-1980s when we began to market our services and various brands to guitar players.
For me personally, I got into the amp scene around the mid- to late 1970s. I just found it to be a nice way to relax from the strain of oversleeping.
PG: Your website shows a large number of amp manufacturers you have replacement/upgraded transformers for. What are your best sellers and why?
SH: There are so many different camps loyal to their particular amp brand, so it would be difficult to single out the best sellers. The best sellers are transitory and change from week to week because guitar amp players are a fickle bunch. That’s why we’ve built the world’s largest catalog of guitar amp transformers where nobody is left out.
But trends tend to follow their own dynamics. And the current worldwide trend seems toward smaller wattage amps—regardless of brand. Conversely, the 100-watt heads are not selling like they used to. Players are gigging with no more than 15 watts and a few pedals. Regardless of playing style, they’re doing just fine abiding by sound level restrictions and kicking ass with the tone we feel Mercury upgraded amps deliver.
These players really get the fact that an amp lacking in tone can’t be fixed with higher power or covered up with a gain mod. An amp that coughs out an asthmatic tone at 50 or 100 watts easily fatigues both music listeners and guitarists. But the audience will stay until the bar closes if the band plays well and sounds great—even with as little as a few watts going through the available PA system.
PG: What can a guitarist expect to hear when upgrading their transformers in a newer amp?
SH: An amp’s transformers are the most important component in determining the quality of amplified guitar tone. And it’s no coincidence that they’re the most expensive parts in an amplifier. Many of the newer amps just don’t have the same “overkill” factor with their transformers as the amps in the ’50s and ’60s. Why? Ignorance and a bean-counter mentality. What’s good for accounting isn’t necessarily good for tone from an amp. Sadly, the people making these decisions are probably not players themselves and don’t seem to realize the damage they’re doing to the industry.
It’s not unusual to find a current production amp with a power transformer running hotter than hell, even without cranking the amp all the way. Or having an undersized, cheaply built output transformer whose sphincter begins to tighten the moment the guitarist reaches for the amp’s volume knob. An amp built around anemic transformers yields only to dull, thin, noisy, fuzzy mids and mushy bass. That’s what makes your notes sound more like farts through a pillow. This overkill factor is probably the only edge that some of the vintage amps have over the newer amps.
We have made it our mission to duplicate the performance of the best original transformer designs of all time. In terms of amplified guitar tone history, these transformers represent the best ever produced.—Sergio Hamernik
Have you ever noticed how most newer amps often weigh less, sometimes a lot less, than the older ones? That’s usually the weight difference between the old and new transformer designs. There is a direct relationship between weight and having transformers that seem to stay cooler and “loaf around” with power to spare, until a player demands more from their amp. It’s like they are waiting around having a card game, waiting for the player to do something. The best vintage tone was born that way. Newer amp tone can be easily improved—if the builder follows some of the same ideas.
Upgrading with quality transformers gives a second chance to a new amp owner to make things right with their tone, by reclaiming that overkill factor. Assuming there are no issues with the amp’s circuitry like bad parts or worn out tubes, a guitarist should hear and feel improvements with the very first pluck of the guitar. They should expect to hear the notes more detailed with overtones, and a quicker and more immediate response to their playing. Clean notes will have less sonic collisions with noise and reveal more bell tones, chimes, etc.
When more distortion is required, the player will sense better control of crunch and when break-up begins to happen. The coughing and hacking that happens when a stock amp is pushed, will vanish with a transformer upgrade. It will be replaced with longer sustains and notes that reach farther. The amp will also sound closer and bigger than the power it puts out—and the bass notes will have a tighter, rounder bottom end. And when pushed, she will still be able to hold that quarter from dropping—no matter how tall her high heels—something most musicians are looking for.
It’s not uncommon for guitarists to report that it took a few weeks of playing to fully realize what they’ve gained in terms of harmonic richness. These players have typically played longer and felt more inspirational emotions sucking them in, as they have invested more time into relearning and becoming reacquainted with their amps.
PG: Many players become very attached to the transformers in their vintage amps. When you create ToneClones or Radiospares and Partridge versions of these classic transformers, how close are they get to the originals?
SH: Radiospares and Partridge are our brand specific clones, whereas ToneClones are “best-of-breed” duplicates culled from the hundreds of other brands that have made transformers over the years.
We have made it our mission to duplicate the performance of the best original transformer designs of all time. In terms of amplified guitar tone history, these transformers represent the best ever produced. In the grand scheme of tone pursuit, these designs are incredibility important and deserve to be considered treasures.
This is an ongoing project for us, spanning almost three decades now. And it couldn’t have been accomplished without the enormous amount of assistance we’ve received from top players and amp collectors around the world.
What about Axiom transformers? Where do they fit in?
The Axiom transformer line takes over where the limitations of vintage transformer design ended. No bean counters here—simply the sincere pursuit of answering the age-old question: What if there were no constraints on budget, time, or material quality to achieve the best possible performance? That’s our objective with the Axiom line.
Axiom transformer designs represent many new approaches—new tone with the best materials and designs money can buy, so they’re not intended for the timid or the low-budget crowd. Check out our FatStacks and SuperStacks for the Marshall DSL and TSL families for interesting comparisons.
PG: Mercury’s vintage transformer restoration service has been gaining a reputation for quality work. Why would someone want to restore a transformer instead of replacing it? And vise-versa?
SH: Some vintage amp owners prefer to pay the extra cost of our restoration services, because it’s very important to them that their amps retain authenticity. Collectables or rarities are valuable. They’re of the “why take chances” mind. The high road. But on the flip side, we have pro musicians who insist on touring with their vintage gear. To play it safe, and not sacrifice the tone of their original transformers, they have their techs replace the stock transformers with Mercury’s. By doing this, they preserve the original transformers from road abuse while taking advantage of our reputation for tone, durability, and warranty. Restoration of vintage transformers is a tricky and highly specialized art. Sadly, too many of the great originals have been lost forever due to technically inept and musically disinterested people. We see attempts at “rewinds” here all the time.
Occasionally, it appears some people confuse “demolition” with “restoration,” and the preservation of the original tone is lost forever. There’s no shortcut to doing a proper restoration.
PG: I understand you’re doing all of your labor and get all of your materials in the USA. How does that impact your business aside from just the straight costs?
SH: Well, we figured that someone has to do it—and we really do make everything here with 100 percent American materials. There are plenty of products out there stamped with “Made in the USA,” but are actually assembled with non-USA, low-price materials. But yeah, we’re the real deal and proud of it.
Building transformers that make an amp sound good requires highly specialized technologies, highly skilled labor, and the right kind of materials. We love music and owe it to the players out there to do all the work “in-house,” so we can keep tight control over every aspect of our transformer designs. It’s really old-school military spec style, so our transformers don’t vary at all from batch to batch. If you need a replacement transformer 10 years from now, it’ll sound exactly the same as the one it’s replacing.
We’re hard-liners when it comes to not playing shell games with a musician’s hard earned dough and quest for better tone. Perhaps I’m a fool for doing it this way, but I was brought up in a musically minded family. From a very early age, I was taught that music is as important and necessary as food. If there is a day our services are no longer needed or appreciated, I’ll pursue my dream of owning a car wash in the valley, and get into the business of making money.
PG: Any new or exciting projects in the works at Mercury?
SH: Yes, but we’re planning on releasing the news sometime around summer. For quite some time, we’ve been fielding requests for accessories to accompany our transformer line. We’re being asked to apply our know-how to other aspects of guitar amps.
PG: Do you have any advice for guitar players and techs in their quest for tone?
SH: Don’t let anybody fool you—every player has the ability to discern the difference between good or bad tone. Unfortunately, there are a few too many self-styled “experts” who irresponsibly dispense advice without having a clue. As a result, we’ve all seen amps completely lose their tone by being modded to death.
There’s no excuse for the old “damn, I’ve done it this way for many years so it must be right” mentality. More than ever, it’s so easy to seek opinion, advice, and help online and elsewhere. I highly recommend the old textbooks from the 1950s and 1960s as a good place to start on vacuum tube audio circuits.
Do your homework and follow what the smart players are doing—improving your tone isn’t that elusive. If what you have sounds good to you, leave it alone. But if you know your amp’s tone could use some improvement, then start where it begins… the transformers. PG
20 watt — Partridge transformer design
It doesn’t take too much digging to find a laundry list of boutique amp builders using Mercury Magnetics transformers in their products. From Mojave Ampworks to Joe Morgan Amps to kits from MetroAmp, builders have found that Mercury knows their iron. While transformers rarely receive the same level of attention of NOS tubes, speakers, or even guitar cables, they are a major contributor to tone. Think about it—the power and output transformers are the start and end of the line with any amp.
Based in Chatsworth, California, Mercury Magnetics has been building transformers for close to 60 years. I recently had a chance to talk with Mercury’s Sergio Hamernik to dig deeper into their roots, find out what one can expect from upgrading their iron, and what sets Mercury apart. Prior to our conversation, I had the opportunity to witness the remarkable transformation of an Epiphone Valve Junior modified from stock to hot-rodded, using one of their transformer upgrade kits. Not only was it a noticeable upgrade, it was a revelation in just how important the role of quality iron in an amp is. But because it is the single most expensive part of any amp, it’s no wonder we see so many modern amp manufacturers skimp on the iron to keep costs down. Let’s see what the passionate, and often hilarious, Sergio has to say about his part of the business.
I’ve been seeing Mercury transformers in amps for at least a decade. When did you get into the amp scene?
This happens to be one of our most often asked questions. Even though Mercury Magnetics’ roots go all the way back to the early 1950s, there are guitar players who are only now discovering us. But if an industry insider like you has been aware of us for at least a decade, then I suppose it means I don’t need to lay off any of our sales and marketing staff.
I would attribute most of our lingering anonymity to the old days. Back then, most of our clients from the audio community preferred to keep us as a trade secret from their competitors and the press. The typical transformer-savvy amp builder also didn’t usually want to share the credit with us, or reveal what their “unique” technical advantage was regarding audio and tone. Consequently, we were asked to maintain a low profile and generic look for our transformers for quite some time. On occasion, a customer in the know will spot a small “MM” mark on a transformer from an older piece of gear, and ask if it’s a Mercury. Odds are that it is.
It was the guitar amp crowd that pushed us to go above ground. Now Mercury gives any electric guitar player or amp restorer a taste of what the pros were using, talking about in their studios, and amongst themselves. Many players have told us their amps increased in value when upgraded with Mercury transformers, and this became evident when insurance appraisers began to contact us for verification. However, it wasn’t until the mid-1980s when we began to market our services and various brands to guitar players.
For me personally, I got into the amp scene around the mid- to late 1970s. I just found it to be a nice way to relax from the strain of oversleeping.
Your website shows a large number of amp manufacturers you have replacement/upgraded transformers for. What are your best sellers and why?
There are so many different camps loyal to their particular amp brand, so it would be difficult to single out the best sellers. The best sellers are transitory and change from week to week because guitar amp players are a fickle bunch. That’s why we’ve built the world’s largest catalog of guitar amp transformers where nobody is left out.
But trends tend to follow their own dynamics. And the current worldwide trend seems toward smaller wattage amps—regardless of brand. Conversely, the 100-watt heads are not selling like they used to. Players are gigging with no more than 15 watts and a few pedals. Regardless of playing style, they’re doing just fine abiding by sound level restrictions and kicking ass with the tone we feel Mercury upgraded amps deliver.
These players really get the fact that an amp lacking in tone can’t be fixed with higher power or covered up with a gain mod. An amp that coughs out an asthmatic tone at 50 or 100 watts easily fatigues both music listeners and guitarists. But the audience will stay until the bar closes if the band plays well and sounds great—even with as little as a few watts going through the available PA system.
What can a guitarist expect to hear when upgrading their transformers in a newer amp?
An amp’s transformers are the most important component in determining the quality of amplified guitar tone. And it’s no coincidence that they’re the most expensive parts in an amplifier. Many of the newer amps just don’t have the same “overkill” factor with their transformers as the amps in the ’50s and ’60s. Why? Ignorance and a bean-counter mentality. What’s good for accounting isn’t necessarily good for tone from an amp. Sadly, the people making these decisions are probably not players themselves and don’t seem to realize the damage they’re doing to the industry.
It’s not unusual to find a current production amp with a power transformer running hotter than hell, even without cranking the amp all the way. Or having an undersized, cheaply built output transformer whose sphincter begins to tighten the moment the guitarist reaches for the amp’s volume knob. An amp built around anemic transformers yields only to dull, thin, noisy, fuzzy mids and mushy bass. That’s what makes your notes sound more like farts through a pillow. This overkill factor is probably the only edge that some of the vintage amps have over the newer amps.
We have made it our mission to duplicate the performance of the best original transformer designs of all time. In terms of amplified guitar tone history, these transformers represent the best ever produced. – Sergio Hamernik
Have you ever noticed how most newer amps often weigh less, sometimes a lot less, than the older ones? That’s usually the weight difference between the old and new transformer designs. There is a direct relationship between weight and having transformers that seem to stay cooler and “loaf around” with power to spare, until a player demands more from their amp. It’s like they are waiting around having a card game, waiting for the player to do something. The best vintage tone was born that way. Newer amp tone can be easily improved—if the builder follows some of the same ideas.
Upgrading with quality transformers gives a second chance to a new amp owner to make things right with their tone, by reclaiming that overkill factor. Assuming there are no issues with the amp’s circuitry like bad parts or worn out tubes, a guitarist should hear and feel improvements with the very first pluck of the guitar. They should expect to hear the notes more detailed with overtones, and a quicker and more immediate response to their playing. Clean notes will have less sonic collisions with noise and reveal more bell tones, chimes, etc.
When more distortion is required, the player will sense better control of crunch and when break-up begins to happen. The coughing and hacking that happens when a stock amp is pushed, will vanish with a transformer upgrade. It will be replaced with longer sustains and notes that reach farther. The amp will also sound closer and bigger than the power it puts out—and the bass notes will have a tighter, rounder bottom end. And when pushed, she will still be able to hold that quarter from dropping—no matter how tall her high heels—something most musicians are looking for.
It’s not uncommon for guitarists to report that it took a few weeks of playing to fully realize what they’ve gained in terms of harmonic richness. These players have typically played longer and felt more inspirational emotions sucking them in, as they have invested more time into relearning and becoming reacquainted with their amps.
Many players become very attached to the transformers in their vintage amps. When you create ToneClones or Radiospares and Partridge versions of these classic transformers, how close are they get to the originals?
Radiospares and Partridge are our brand specific clones, whereas ToneClones are “best-of-breed” duplicates culled from the hundreds of other brands that have made transformers over the years.
We have made it our mission to duplicate the performance of the best original transformer designs of all time. In terms of amplified guitar tone history, these transformers represent the best ever produced. In the grand scheme of tone pursuit, these designs are incredibility important and deserve to be considered treasures.
This is an ongoing project for us, spanning almost three decades now. And it couldn’t have been accomplished without the enormous amount of assistance we’ve received from top players and amp collectors around the world.
What about Axiom transformers? Where do they fit in?
The Axiom transformer line takes over where the limitations of vintage transformer design ended. No bean counters here—simply the sincere pursuit of answering the age-old question: What if there were no constraints on budget, time, or material quality to achieve the best possible performance? That’s our objective with the Axiom line.
Axiom transformer designs represent many new approaches—new tone with the best materials and designs money can buy, so they’re not intended for the timid or the low-budget crowd. Check out our FatStacks and SuperStacks for the Marshall DSL and TSL families for interesting comparisons.
Mercury’s vintage transformer restoration service has been gaining a reputation for quality work. Why would someone want to restore a transformer instead of replacing it? And vise-versa?
Some vintage amp owners prefer to pay the extra cost of our restoration services, because it’s very important to them that their amps retain authenticity. Collectables or rarities are valuable. They’re of the “why take chances” mind. The high road. But on the flip side, we have pro musicians who insist on touring with their vintage gear. To play it safe, and not sacrifice the tone of their original transformers, they have their techs replace the stock transformers with Mercurys. By doing this, they preserve the original transformers from road abuse while taking advantage of our reputation for tone, durability, and warranty. Restoration of vintage transformers is a tricky and highly specialized art. Sadly, too many of the great originals have been lost forever due to technically inept and musically disinterested people. We see attempts at “rewinds” here all the time.
Occasionally, it appears some people confuse “demolition” with “restoration,” and the preservation of the original tone is lost forever. There’s no shortcut to doing a proper restoration.
I understand you’re doing all of your labor and get all of your materials in the USA. How does that impact your business aside from just the straight costs?
Well, we figured that someone has to do it—and we really do make everything here with 100 percent American materials. There are plenty of products out there stamped with “Made in the USA,” but are actually assembled with non-USA, low-price materials. But yeah, we’re the real deal and proud of it.
Building transformers that make an amp sound good requires highly specialized technologies, highly skilled labor, and the right kind of materials. We love music and owe it to the players out there to do all the work “in-house,” so we can keep tight control over every aspect of our transformer designs. It’s really old-school military spec style, so our transformers don’t vary at all from batch to batch. If you need a replacement transformer 10 years from now, it’ll sound exactly the same as the one it’s replacing.
We’re hard-liners when it comes to not playing shell games with a musician’s hard earned dough and quest for better tone. Perhaps I’m a fool for doing it this way, but I was brought up in a musically minded family. From a very early age, I was taught that music is as important and necessary as food. If there is a day our services are no longer needed or appreciated, I’ll pursue my dream of owning a car wash in the valley, and get into the business of making money.
Any new or exciting projects in the works at Mercury?
Yes, but we’re planning on releasing the news sometime around summer. For quite some time, we’ve been fielding requests for accessories to accompany our transformer line. We’re being asked to apply our know-how to other aspects of guitar amps.
Do you have any advice for guitar players and techs in their quest for tone?
Don’t let anybody fool you—every player has the ability to discern the difference between good or bad tone. Unfortunately, there are a few too many self-styled “experts” who irresponsibly dispense advice without having a clue. As a result, we’ve all seen amps completely lose their tone by being modded to death.
There’s no excuse for the old “damn, I’ve done it this way for many years so it must be right” mentality. More than ever, it’s so easy to seek opinion, advice, and help online and elsewhere. I highly recommend the old textbooks from the 1950s and 1960s as a good place to start on vacuum tube audio circuits.
Do your homework and follow what the smart players are doing—improving your tone isn’t that elusive. If what you have sounds good to you, leave it alone. But if you know your amp’s tone could use some improvement, then start where it begins … the transformers.
Source: https://www.premierguitar.com/articles/Builder_Profile_Mercury_Magnetics
Earliest 50 watt — single 120V primary — 5V tube rectifier winding. This transformer design is from within the first 12 Hiwatts built! Partridge transformer design
Earliest 50 watt — UL taps — 8 & 16 Ohm secondary taps. Within the first 12 Hiwatts built — Partridge transformer design
50 watt — Partridge TG 6556/2 (H6162 J) –3.8 kΩ primary, 8 & 16 Ω taps
Vertical mount — bolt hole spacing is 2 1/2″ x 2 1/2″
The newest family of transformer designs from Mercury. APS transformers are built and specifically optimized for today’s amps and today’s tubes. Due to power, modern tube production, design and chassis “real estate” limitations, not all modern amps can be modified or upgraded to handle the full-on affects of our Axiom, ToneClone, Radiospares or Partridge transformers. APS transformers correct many of the design limitations of the stock transformers to give you the most your amp can offer. APS transformers make your amp more reliable and better sounding. If you depend on your modern amps for a living, then you need the peace of mind APS transformers will give you. Transformers made to take the punishment of being on the road and keeping your amp running.
All APS transformers come with our Automatic Thermal Resettable Fuses. Ask your Mercury Sales Rep about this important new feature! All APS transformers come with both our 10-year Workmanship Warranty. APS transformers may be used for upgrades or replacements for modern tube-based guitar amp applications.
To find out more, or discuss to the characteristics of the different transformers sets available for your amps, give us a call or email.
Mercury brands marked with Plus+™ logo are cloned transformers with minor additions. You’ll only see the Plus+ logo on our ToneClone, Partridge and Radiospares catalog listings. They’re modified, without tampering with the original tone, to match today’s power company voltages and employ better noise immunity.
Variations include: added input power taps, added secondary taps, and other minor enhances to the originals. More good news — all Plus+ transformers come with both our 10-year Workmanship Warranty and Tonal Guarantee.
To find out more, or discuss to the characteristics of the different transformers sets available for your amps, give us a call or email.
Truly inspirational and superior tone has led you to the final link in the chain – Mercury Magnetics. Premium guitar amplifier power transformers, output transformers and chokes.
100% American made — no hidden imports — we really do make ’em from scratch, right here in California!
100% handmade and hand-tuned using only hand-wound components. We never compromise or play bean-counter games by short-cutting, attrition or using cheaper materials. Each and every transformer is consistent. If you ever need to replace one of our transformers, your amp won’t lose its tone — your replacement will sound exactly the same as the original.
American-made steel — we’re the only transformer manufacturer who custom orders, from an American steel mill, the unique alloys used in our transformers. These alloys are not only made here in the USA to military specifications, they are not available anywhere else in the world. They’re the same alloys used in the all-time best-sounding transformers during the “sweet spot” era (pre-1965) of guitar amplification history.
Things are never stagnant around here. Mercury maintains active and ongoing R&D (research & development). All kinds of new and exciting-sounding transformer designs (Axiom series), as well as our ongoing cloning of outstanding output transformers mined from the great old amps (ToneClone series). For vintage British amp freaks, check out our Radiospares, Hiwatt and Partridge series. And many modern amps can be upgraded with our APS series — our newest line of guitar amp-specific output transformers.
For any popular amp design we’re likely to have not just one but several transformers for different purposes and different tonal characteristics. It’s always a smart idea to discuss replacement, restoration or upgrading with your Mercury rep. — you’ll find his input invaluable.
Our output transformers are found in the amps of virtually every major player in the world. Many specify Mercury and won’t play an amp without them.
Mercury transformers are standard components or factory upgrades available in virtually all high-end boutique amps, including Fender’s boutique and custom shop lines.
Mercury transformers are so highly rated that they typically increase the value of any amplifier they’re installed in.
All Mercury Magnetics® products are 100% handmade in California, USA.
Copyright © 1954-2018 by Mercury Magnetics. All Rights Reserved. Mercury Magnetics, Mercury Vintage, Partridge, FatStack, SuperStack, NewVolt, Mini-Choke, Multi-Choke, Mercury Custom Shop, Mercury Boutique, “The Heart & Soul of Your Amp,” “Holy Terror,” “Bad Guitar Tone — Whatever Its Evil Mission It Must Be Stopped!”, “Champ 600 Upgrade,” “XLG Upgrade Kit,” “Mean 13” and “The original British amp tone — shaken, but not stirred,” “Our Transformers are Stacked,” “The Essential Building Blocks of Your Tone,” “Mercury Studio-Pro Upgrade Kit for the VOX AC4tv,” UTM (Universal Transformer Mount), Amp-Saver and Copper-Tone are trademarks licensed to Mercury Magnetics. Axiom, ToneClone, Radiospares, VoodooScrew, Multiple Arrayed Geometric Inductive Coupling (M.A.G.I.C.), and APS (American Pro Series) are registered trademarks licensed to Mercury Magnetics. All other companies, products and trademarks mentioned on this website are trademarks of their respective owners. Unless otherwise noted Mercury Magnetics is not affiliated with any of these companies.
Mercury Mod and Upgrade projects and their documentation are the result of technical investigations made by the engineering staff of Mercury Magnetics. The disclosure of the information herein may pertain to proprietary rights, and the furnishing of these documents does not constitute an expressed or implied license to use such materials.
Mercury Magnetics® transformers and other products are in compliance with the European Union RoHS Directive 2020/95/EC with respect to the following substances: lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (CR (VI)), polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE).
Mercury Magnetics® founded in Southern California in 1954 and incorporated in 1968.
CAUTION!
The voltages in your amplifier can be dangerous. Transformers and chokes are not user serviceable parts. Installation of these components should always be performed by an experienced technician.
The simple ability to use a soldering iron is not enough to qualify a “do it yourself person.” Those who are inexperienced in working with electronic circuits should never attempt to service their amplifier. Household line currents can be deadly!! Transformers, chokes and large filter capacitors can store a dangerous charge for several days or more after the amplifier has been unplugged. Never touch the terminals of such devices without being certain of their charge status. Risk of shock and damage to equipment may result from mishandling and/or improper use of these components. Please use common sense and always think safety first. After all, tone is most enjoyed when you are alive to hear it.
Your quest for truly inspirational and superior tone has led you to the final link in the chain – Mercury Magnetics. Premium guitar amplifier power transformers, output transformers and chokes.
Transformer sets are often misunderstood, yet vital musical components. They’re integral to the nuances of your guitar amp’s sound. Far more than tubes, speakers or other amp components, the transformers establish the platform for shaping your amp’s unique sound.
Today’s players are more informed and demanding than ever. They hear the differences and know that both transformer design and build-quality have a dramatic effect on their tone. Indeed, if your tube-based amp is suffering from bland and unexciting tone then it’s probably related to low-end or poorly designed transformers. As amp designers, techs and manufacturers have discovered, the practice of dumping generic, low-bidder transformers into their amps doesn’t cut it any more. And now you know why.
Within the player community no other company commands as much respect as Mercury Magnetics. You can depend on our uncompromising, fanatical build quality, consistency and reliability.
All of our transformers are 100% handmade by us here in California, USA. They come with an unheard of 10-Year Workmanship Warranty as well as a money-back Tonal Satisfaction Guarantee.
Did you know that tube-based guitar amp transformers are unusual and very different from industrial as well as audio transformers? And did you also know that it is impossible to engineer the “perfect” guitar amplifier transformer from strictly “by the book” specifications? Interestingly, almost all of the great-sounding amp transformers contain either flaws, “happy accidents,” or have other issues in their construction that were not part of their original specifications.
Decades ago, when Mercury’s engineers first discovered these curious phenomena, the music industry was already in the process of losing its references to tone. In the throws of converting to solid state, tube and transformer platforms were mistakenly being relegated to relics of the past. Those who knew the original technology were either retiring, dying off, or jumping ship for the “new improved” way of doing things. By the time we collectively began to realize what was happening to guitar tone, it was almost too late. “Old school” manufacturing had been all but shut down and as quality dwindled N.O.S. (new old stock) components became the last bastion of our tone.
It was during those Dark Ages that the transformer connection to tone was almost lost completely. However, Mercury was there as a hold out — and even when it wasn’t fashionable, never compromised. But as often happens, when an older era fades, the remnants of what made it great were readily available to study. And like archeologists, Mercury’s engineers began sifting through the bones of the most coveted old amps in an attempt to discover what made them better, and often times so different than others.
The resulting products of those studies were the earliest ToneClone and Axiom designs. Mercury quite literally evolved a new science of guitar amp transformer design for tube-based guitar amps from there, and has continued to innovate and revolutionize it since. Perhaps few people realize the significance of these discoveries and the resultant developments. But without Mercury’s catalog of transformer designs, guitar tone as we knew it would have been lost.
In part I of our Marshall JTM-45 transformation process, we installed a point-to-point board from Metropoulos Amplification (www.metroamp.com) and began to hear the positive results of our test Marshall as it came to new life.
Now, in Part II of our continued Marshall JTM-45 transformation, we move forward with two additional changes in addition to having the opportunity to compare the final results to an original 1964 badge-logo Marshall JTM-45. The two changes that we decided to perform were to swap out the stock output transformer to a Mercury Magnetics™ (www.MercuryMagnetics.com) Axiom® O45JT-C model as well as to upgrade the board’s capacitors to those made by SoZo Amplification. To say that we were excited as well as just plain curious about the final results, especially when we could now compare it to an original JTM-45 — is an understatement.
We contacted Paul Patronete at Mercury Magnetics™ and he hooked us up with the Axiom® output transformer. Paul added that the Axiom® O45JT-C is a custom version output using Teflon wire instead of the normal UL1015 vinyl wire. The Axiom® O45JT-C output offers 8 & 16 ohm secondary taps. When it comes to output transformers for the JTM45 amp, Mercury Magnetics™ offers a plethora of options beyond the stock, cloned, vintage replacement. Options available in the Axiom® line of output transformers are primaries optimized for KT66/6L6/5881 tubes or EL34/KT77 tubes. Secondaries with just about any output impedance combination that one could want. Many of these custom Axiom® models feature “mil-spec” Teflon wire leads with silver tinned, nineteen strands of high purity copper. All of the Axiom® transformers are hand wound from period correct specimen, vintage blueprints. One of the more popular Axiom® pieces that Mercury Magnetics™ offers is an exact clone of the highly coveted Radio Spares output transformer. The Radio Spares output is from the early original, first run Marshall JTM-45 production amplifiers. Mercury Magnetics™ offers several versions of the Radio Spares output. One of the most popular versions is a Teflon wire leaded version. The Radio Spares transformer is well-known for its association with the earliest Marshalls and according to Paul is what you’d find in the famous Eric Clapton “Bluesbreaker”-era amp.
Those that have listened to or played through a properly running Marshall JTM-45 know the sound. It’s a smooth and naturally compressed distorted tone that when pushed will provide just enough crunch to know it’s characteristically a Marshall, but without any of the “buzzing bees” preamp tones characteristic in high-gain preamp-gain emphasized amplifiers. As you push the volume controls up higher on a the best JTM-45s, it’s clearly the sound of rock with its fat bottom end, lovely harmonic overtones, and sustain that sits well with the best blues and classic rock tones heard. All of this packaged in an amp that really is one of the most dynamic and player-responsive amps ever built.
The reissue JTM-45, while certainly not a “bad” amplifier on its own, really does lack much of the detail and smoothness that is really much easier to grasp and identify when heard. For example, the reissue JTM-45 in stock form would thicken up appropriately with the expected tube compression when turned up, but it clearly was not as smooth. There are definitely some tones that sound a bit “grainy” and edgy that a properly running original JTM-45 doesn’t have.
A project such as this JTM-45 reissue transformation offers an exciting opportunity for those serious about maximizing their tone, but either don’t have or don’t want to shell out the prices for the originals. As of this writing in early 2004, script-logo JTM-45s are commanding a minimum of $4,000 and the better examples are going for more than that. Our badge logo JTM-45 featured here generously on loan for the story has a value that may well be approaching $10,000 by today’s estimates.
With that aside, we should start out by saying that this is not a thorough “apples-to-apples” comparison between the two amps. To be 100% fair, ALL the components would have to be altered to the exact specifications of our 1964 badge-logo Marshall JTM-45 and that really wasn’t the point. The point of these transformations was to get the stock reissue JTM-45 sounding more like the “real thing” as described above with regards to the powerful, smooth and dynamic Marshall tone.
Another issue beyond the component values is that we’ve opted to keep the power transformer in stock form for the time being in the JTM-45. As a result the transformers will supply a different amount of B+ current to the plates and so it will not respond in exactly the same way as the original Badge logo model.
One final, and perhaps most important point, which Mercury Magnetics™ vice-president Sergio Hamernik added: “The transformer in a 30-year old amplifier will sound characteristically different as it ages compared to a new replacement, even if the replacement is built with the same materials.” And while the component materials and manufacturing methods used by Mercury Magnetics™ are made to the exact same standards as the originals (Sergio also added “Every turn, every layer, is copied and blueprinted exactly, including any original manufacturing anomalies found during our rewinding process of the original, vintage specimen, Sergio emphasized that the ToneClone™ series transformer will still sound different, but “like the original did in the amp when it was new” and not like the tone of the aged 30-year-old transformer. Since much of our favorite tones were recorded at least 20 years ago, perhaps this isn’t such a bad thing?
Sergio did suggest breaking in the new Axiom® transformer with 20 to 40 hours of hard playing time. He also said that this break-in period will get the transformer about halfway there to that 30 year seasoned tonality. Thermal cycling and running magnetizing currents through the transformer (playing the amp) will definitely sweeten things up in that period of time.
We could and may still make further changes to the reissue JTM-45 in the future and report back. However, with the point-to-point board, reduced “vintage” filtering, and tube swap that we performed last time around, along with the planned replacement of the on-board capacitors and output transformer for this second round, we thought that we’d be in really good shape with the final tonal results of this amp. And for those that missed it previously, we had previously written about Mercury Magnetics™ output transformers used in a 50 watt Marshall and were very pleased with the results. We anticipated nothing but the same results with the change in the reissue JTM-45 this time as well.
So far our project amp has KT-66 power tubes, 32x32uf and 16x16uf filter caps and a Metro Amps point-to-point circuit board. At this stage, we were very satisfied with the results. We could have stopped here and had a real tone machine, but we wanted to see if we could get even closer with a few more changes. Sonically, the reissue at this point prior to the SoZo caps and output transformer change, did exhibit more of the growl and gain of the original, but it still wasn’t nearly as smooth or as dynamically punchy as the badge logo JTM-45 was.
Mike Mullen on testing the SoZo Caps
While waiting for our Mercury Magnetics™ output transformer, I read about some capacitors that created quite a buzz on the Plexi Palace vintage amp forum. We found that SoZo Amplification was offering custom made capacitors aptly named “mustard caps”. They are obviously mustard yellow but apparently these caps are also made to the same specifications as the yellow mustard capacitors which were originally found in tube amps from the 1960s and 1970s. These little yellow jewels keep the foil thickness, polyester film dielectric and voltage ratings the same as the originals. In addition to the material makeup of the capacitors they also share the same physical dimensions. According to the SoZo Amplification website, the physical shape has a lot to do with the sound because it changes the slew rate.
The SoZo Mustard Cap is longer and thinner as compared to most high production caps readily available today. The additional length results in a different signal delivery time, changing the harmonics of the capacitor and yields smooth, clear, thick lower-mids. Polyester film was chosen because of its deeper tonal character and aluminum foil was chosen to exactly recreate the capacitor’s original sound and performance. SoZo also chooses to use tin-coated pure copper leads, which SoZo claims aids in the retro mustard cap sound.
I promptly received the package containing five .022uF and three .1uF SoZo Mustard Caps and soldered them in. In about thirty minutes all the caps were installed and I was ready to hear the results.
I flipped on the power, plugged in a Seth Lover-loaded Gibson Les Paul and let the KT-66’s warm for a few minutes. Turning off standby, I decided to start with my best impression of Angus Young from AC/DC to entertain my neighbors. What I heard from my Celestion loaded 2×12 cabinet was clear, warm guitar tones that sounded ALIVE! The tone of the amp was basically the same, but it was much clearer, richer and more complex than what I heard before. I was very pleased with the improvement.
Anyone that is due for a cap job on his or her favorite amp should really give the SoZo “mustards” a try and change those along with the electrolytics while you’re already there. I think the results are very satisfying and the cost runs about the same as a decent guitar cable. The caps can be ordered direct from SoZoAmplification.com or from MetroAmp.com. MetroAmp.com is offering these SoZo caps individually or they can be ordered with one of their point-to-point boards.
A final point is that SoZo amplification states that there is a break-in period for the capacitors and that the tone will actually improve and be at best form sonically sometime between 40 and 70 hours of use. While I’m not there yet as far as hours of use, I definitely like what I’m hearing so far!
Installation and listening to the Mercury Magnetics™ O45JT-C Output Transformer
The Axiom® 045JT-C output transformer is part of the Mercury Magnetics™ Axiom® ToneClone™ series, and is 100% hand wound in the USA by Mercury Magnetics™ at their factory in Southern California. Mercury Magnetics™ offers a number of transformer clones for JTM-45 amplifiers as Marshall used a few different suppliers during different times with its own JTM-45s originally. Some people may have a preference for the earliest transformer equipped in JTM-45s, which were those built by the Radio Spares company. According to Mercury Magnetics™, the Radio Spares output transformer has more “high-fidelity” characteristics in its tone. According to Paul at Mercury Magnetics™, their Radio Spares clone is a special, intricate transformer that produces a subsequently wider frequency response and in some ways mirrors other transformers in design such as the early famous Partridge units in the Hiwatts.
However with that said, there aren’t comparatively as many JTM-45s equipped with original Radio Spares output transformers so we went with the more commonly found transformers as found in later JTM-45s. When speaking with Paul, he also noted that the original, vintage “Radio Spares” equipped JTM45 amplifiers are highly sought after and can command big dollars in the musical marketplace. Perhaps we’ll experiment with one in the future to hear the differences for ourselves.
The installation of any output transformer, while seemingly “simple” (“hey there’s only a few wires right?”) should actually only be performed by either a professional technician or by an enthusiast with a minimum of Electronics 101 knowledge, including the ability to read schematic diagrams, an understanding voltages and polarity, etc. This is the advice directly from Mercury Magnetics™.
The transformer includes a wiring diagram sheet listing the color-coded primary and secondary wires, and these may not necessarily match the wiring in your amp. Mercury Magnetics™ also warns that installers put safety first, as there are literally hundreds of AC volts that can come off of the primary. A typical technician will charge 30 to 90 minutes of labor for the installation, which can average anywhere from $50 to $150.00. Prices and the time required to install an output transformer can vary from technician to technician.
*Installation tip: anyone planning to replace both the output transformer and circuit board may want to remove the old circuit board and output transformer first and then mount the new transformer. Then you can install the point-to-point board and not have to mess with it later to get at the output transformer mounts.
After some time and with the transformer installed, it was time to play! But first, a few minutes with the badge-logo JTM-45….
Taking a Classic for a Test Drive
The original badge-logo Marshall JTM-45 is truly an example of a wonderfully responsive guitar amplifier. In its best state, it can provide a range of tones that vary between the liquid and thicker lead tones of early Clapton, to the warmer side of the Marshall crunch a la AC/DC that we all know and love. The vintage badge-logo JTM-45, that we have the good fortune of borrowing courtesy of our good friend Woody (thank you!), had recently gone through a full check-up through southern California’s own Plexi Palace, so we knew that it was in fine form.
And it certainly sounds like it. No other Marshall seems to be as well suited to provide such a wide tonal range as well as being able to provide a feel with beautiful harmonics and compression as a JTM-45 circuit. The sense of dynamics that can be controlled with one’s technique was right on the money. This JTM-45 plain and simply is THE ultimate blues and rock amplifier.
It stings and bites as musically as one could imagine with a Fender Stratocaster using the bridge position pickup with the Marshall’s channels bridged and the volumes set at about 7. With the neck pickup, the tones are fluid and with a bit of a gain boost from a floor box could easily capture the full sustain similar to what a player like Eric Johnson would get. The power output on the amp is moderately high, but at the JTM’s power range, it really is a nice match against any solid-hitting drummer and the perfect club amp for small and mid-sized venues.
With a Gibson Les Paul in hand loaded with LegendaryTones.com’s current favorite Seymour Duncan Antiquities and running the badge-logo JTM-45 through a basket weave Marshall cabinet (NOT the cabinet photographed here which is an earlier pinstripe) with original 25 watt greenbacks, the tone of the bridge pickup was pure AC/DC circa “Powerage” when running the volumes at about 6. With the volumes set at 7, the added gain and thickness moved into “Highway to Hell” territory. Switching to the neck pickup provided a wallop of a fat tone that seemed like it could sustain for days. Think early Cream here.
Listening in on the reissue JTM-45
After that experience with the 1964 badge-logo JTM-45, part of me didn’t want to turn the amp off, but alas it was time to move to our modified reissue. Running the same controls (and in fact the same tubes were used and setup in both amps) and equipment, I started playing the reissue with the Strat first. The immediate first impression: the reissue JTM-45 felt great – the same feel of compression and control of the dynamics was there. And there was also a noticeable improvement between the circuit since the change of both the output transformer and SoZo caps. Besides having a bit more power and punch in the signal, these changes really seemed to smooth out the reissue JTM-45’s tone and were definitely much more pleasing to the ear.
But specifically what were the differences between the reissue and the original? Well, the modded reissue stood out with a bit more attack in the high frequencies. It’s definitely a bit of a brighter amp than the 1964 badge-logo, but not by a great deal and not bright in such a way as to be “piercing.” The reissue JTM-45 could definitely mimic the original with a simple reduction of presence and treble controls and it did very well. Also, both SoZo Amplification and Mercury Magnetics™ told us that there is a break-in period for the parts to obtain their final adjusted tone. Again, for the SoZo caps, its 40-70 hours, and Mercury Magnetics™ stated the average break-in period should be a minimum of 20 hours of hard playing time with its transformers.
All said, we couldn’t wait that long nor did we have the time to play continuously to then report on the changes, but maybe we’ll add a brief report in the future after the break-in period.
When switching to the Les Paul with the newly transformed JTM-45, the same characteristic bold crunch with a warm full bottom end was evident. The modified reissue JTM-45 is definitely smooth when overdriven and power chords are a thrill to bash out in AC/DC style. Leads in both pickup positions of the Paul sang nicely. The neck position is always powerful with the JTM-45.
Final Thoughts….
In both amps, the feel, sustain, and tone was tremendous. The reissue in its current form has a little bit more of a faster attack, while the original badge has a bit more of a relaxed sag to it characteristically. It’s also a little bit darker. That said, we expected differences especially considering that each amp’s circuits are not identical. But what they do both share together is the original Marshall tone that we grew up on and know and love. And the fact that this tone can be captured without the need to hunt down a costly original is a nice thing for players indeed. There is something to having an original — it’s a testament to a wonderful period of musical history that NO reissue would ever be able to capture from that perspective. But at the same time, one thing that the reissue has going for it in its favor is the fact that most players would feel much more comfortable taking it out to a gig or the all-night jam. I would be a bit paranoid taking out the original personally.
It’s a shame that some of our greatest musical instruments, whether we’re talking about a ’59 Les Paul or an original Marshall amp, are so highly-valued in this day and age that it’s difficult to “enjoy” playing them. However, isn’t it a nice thing that companies such as those featured in this article are so passionate about their products and in finding ways to empower musicians with great tonal solutions today? I’ve said it before — we’re definitely living in times of a tonal renaissance with the options we have and the number of great instruments, effects, and amps that we have available to us.
And though some people may say that, “they don’t build them like they used to,” I would actually agree. In the case of these dedicated companies and people, I believe they’re in fact building them better than they used to with care and meticulous detail that may not have always been present back in the day.
Source: https://mercurymagnetics.com/pages/news/LegendaryTones/LegendaryTones-02.htm
Last month, Sergio Hamernik, head honcho at Mercury Magnetics, walked us through the intricate process of rewinding a vintage transformer. This month, we dig a little further into the details of winding, materials, the ways age affects some transformers, and why some of them fail.
When you rewind a transformer, do you use the same wire used in the 1950s and ’60s?
No. We use high-purity, oxygen-free copper magnet wire made in the U.S.A., and we use it because of its tonal properties – it’s sonically superior and more consistent than the wire used in the ’50 and ’60s. Wire, back then, had about half the temperature and electrical performance capability of Mercury’s standards.
We, as players, would prefer to use wire from the ’50s and ’60s compared to offshore and south-of-the-border wire. We tried them, thinking we’d save our customers some dough, but test results yielded dull tone and we saw inconsistent batches with too many instances of insulation breakdown. The stuff was not even up to the standards of vintage wire. Further, in real-life tests putting amps through their paces, the sonic differences were noticable to the guitar players here at Mercury, and those working for the recording studios here in Southern California.
Have you ever seen a negative effect of age on a transformer?
In some cases, yes. Sometimes, your ears pick up on the effects of aging before you realize what’s happening – they produce dark, dull, and fuzzy tones with a general sense of lower output volume.
If anything in a transformer suffers from aging, it will most likely be the core. Two major contributors cause a negative effect of aging and affect your tone. Before World War II, the science of processing iron was not up to snuff. It was difficult to boil out residual carbon, and even a miniscule amount of carbon in older iron causes it to age. As an iron core ages, its magnetic conductivity begins to poop out, slowing the transformer’s responsiveness with increasing losses. The result is less output with only lower mids breaking through.
During WWII, the war effort created a shortage of iron. So, many transformer companies made cores from sheet metal, like that used to make soup cans! These had the wrong kind of iron and harbored plenty of carbon, to boot – do not confuse iron with steel! Finally, when silicon was implemented to help force the carbon out of post-war iron, transformer iron became stable enough to outlast us all.
Another contributor to transformer aging comes from humidity. Amp owners who live in humid climates have noticed their tone changes over the years, especially if their older amps had transformers built around paper bobbins, which have always run the risk of moisture absorption affecting tone. Conversely, we found that transformers with plastic bobbins weren’t likely to suffer tone degradation via moisture saturation. A couple excellent examples are the original Partridge and Radiospares transformers from England – with the fog and rain they experience, these transformers held up quite well. That may explain why coating paper in wax was attempted early on, and to verify that humidity affected output transformer tone, we flew in transformers from amps made in the ’60s that had never left the U.K., all with paper bobbins, and put through a dehumidifying process, then re-sealed them in varnish and gave them a full bake. The owners freaked out and thanked us for giving them their original tone back! One called to thank us personally when he realized it was his tone fading over the years, and not his ears! He said that as time passed, he noticed less treble and a lot less note separation and definition. Others had this mastaken belief that their amps were getting too old to play.
Obviously, the rewound transformer for the 1960 Vox AC15 we’ve been working on the last few installments won’t be dipped in wax. What will you use to insulate it?
It’ll receive a fresh dip of varnish.
What can we expect the differences to be between the rewound transformer and the original?
It should sound as good as when it left the showroom in 1960. The only other option, as far as upgrading the tone, would be to try one of our ToneClones, which are copies of the finest celebrity-owned and played “pick of the litter” transformers. It’s likely you’ve heard these transformers in action on your favorite recordings.
Has a rewound transformer come back to you shortly after it was sent out?
Yes. Installer error happens, and if you don’t find and fix the problem that caused the transformer to blow in the first place, you’re setting yourself up for a repeat performance.
Another thing that’s fairly common is the use of N.O.S. tubes, usually bought from an online auction. We had a customer who, after installing his rebuilt output transformer, decided to re-tube his amp with 40-year-old American-made originals. As luck would have it, one of the tubes shorted and caused a different failure in the newly rebuilt transformer.
Is every old transformer destined for a rewind, or could some go on forever?
Not every old transformer will need to be rewound, if taken care of poperly. Most may outlast the “Iron Age” of guitar transformers, which we’re living in now. The push for solidstate technology is tenacious enough to replace tube-/transformer-based amps in the long term. Tubes may go, but they’ll have to pry the transformers from my cold dead fingers before I’ll give them up!
We recently put transformers of all kinds – old and new – to the test by volunteering to help flood victims in Nashville. We offered to test and restore water-damaged transformers, and encountered some pretty nasty stuff. Yet, less than five percent of them needed to be rewound – namely, those with paper bobbin insulation or amps that had been turned on before the transformers were tested. Some transformers were from amps that had been submerged in sewage for weeks! The odor was so foul we had to air them out, and the staff actually had to draw straws to determine who was going to work on them.
You must have your share of unpleasant jobs….
Man, you got that right! But there’s nothing like the fresh smell of varnish in the morning to help one deal with that challenge. We did manage to extract the moisture and re-seal these transformers with varnish. The sacrifices you have to do to help fellow musicians….
Last month, we dropped off a toasted output transformer from a 1950 Vox AC15 with Sergio Hamernik and the team at Mercury Magnetics. From a suspicious pin-sized burn in the transformer’s outer paper insulation, they were able to determin probable causes for the transformers untimely demise. Then it was onto the rewind process! So, is it over for this amp’s output transformer?
VG: What goes into the process of rewinding a transformer?
We begin the restoration process with a thorough testing of the transformer’s electrical performance. Then we put the transformer’s insulation system through its paces – checking its integrity, making sure the voltages inside the transformer stay where they belong and not going wonky by arcing over to neighboring windings.
Consider these steps a weeding out process to find the proper candidates for restoration. If the transformer in question passes, then we return the transformer back to its owner or tech. Believe it or not, about 1-in-4 transformers we receive pass our testing! We offer free-of-charge transformer testing to anyone – all they have to do is cover the shipping costs. Some of these transformers are sent to us simply to make sure that all is operating well within specs – essentially for a second opinion.
We consider it a “sin,” a violation of our sense of professional ethics, to tamper with a perfectly good transformer. Rewinding or restoring transformers is a service born out of our passion for preserving tone at its highest standards. Properly rewinding transformers is a time-consuming and costly endeavor. The reality is that our rewinding service is not exactly a profit center. Who knows, maybe one day we’ll sober up and quit doing it altogether. But it does break our hearts when we find vintage transformers ruined by feeble attempts at rewinding by people who do not posses the necessary skills, or who do not have an interest in or knowledge of guitar tone.
If the transformer does fail our testing in any way, then we deem it unsafe to be put back in its amp. Now the process of rewinding begins. A large part of this process is akin to archaeology, or perhaps autopsy. We want to find out precisely how it was made and discover who or what killed it. So the first thing we do is remove the core stack and catalog each plate for original position and sequence. Check out the photo of your core completely apart and tagged. We did find some rust and will do our best to preserve it.
it. So the first thing we do is remove the core stack and catalog each plate for original position and sequence. Check out the photo of your core completely apart and tagged. We did find some rust and will do our best to preserve it.
We actually talked about that in an article we did back in the August 2009 issue of VG.
Yes that’s right. That patina of rust on the core of your transformer is an indicator of better quality iron that is ideally suited for guitar tone. The rust itself is working in league with the iron to assure that level of tonal performance. Modern day technology messes with the original iron processing recipes by adding rust inhibitors and other fillers. They’ve short-cut the more time-consuming and costly metallurgical processes – just like how auto makers are putting in more plastic than metal in their cars. Iron is an amazing magnetic conductor until it gets diluted or polluted with things that are better suited for non-audio applications. So if I had my choice, I’d prefer to play an amp with rusty transformers delivering the tone I want rather than an amp with pristine rust-free transformers that make the amp sound like it’s got a sock stuffed down its throat.
So the original core will go back in the transformer?
Yes. Since you have the right kind of iron core we’ll reassemble it the way we found it, then retune it to the original factory specs. If you were stuck with a transformer that had inferior core material, then we would suggest swapping it with Mercury upgrade iron.
It’s come to our attention that many current production transformers marked with “Made in the U.S.A.,” are actually using offshore materials, i.e. magnet wire and steel. More accurately they should read “Assembled in the U.S.A.” These self-defeating transformers are good candidates for our upgrades rather than rewinds.
Cores are the first component out and the last in during the course of restoration. An interesting fact: cores are never at fault when it comes to a transformer breakdown. The core is removed solely for us to gain access to the coil of the transformer. Taking apart the coil is a surgical process that begins our forensic investigation – like the crime shows on TV. Unpeeling a coil is quite revealing and will tell us the story of what happened. Under interrogation the coil always tell us the truth. A body of a man is wheeled in to the morgue. His wife insists that he shot himself while cleaning his gun – but the autopsy’s evidence proves otherwise. Now she’s under suspicion.
Well the coil of your transformer quickly spilled the beans. Remember that small black spot we noticed on the outer wrap of the coil? Sometimes there are innocuous blemishes in the form of spots that may appear on the surface of paper and are nothing to worry about. However, what we normally find in fried transformers is that the burn begins somewhere in the middle of the coil and works its way out – causing an exit wound. In your case the failure was not typical. Yours was an entry wound.
This is important because it indicated to us that it was killed by a sharp instrument that penetrated the outer insulation that broke through and severed two turns of the fine wire that make up ½ of your primary winding. Meaning that only one of the two power tubes was operational. The damage to the entire transformer was limited to that spot and only the very top layer of the magnet wire. Those broken wires were arcing across each other and taking advantage of the oxygen available from the perforation of the outer wrap to form that black spot. Further evidence to support these findings is the fact that the rest of the winding, all the way down to the bobbin, was unharmed.
This type of injury is caused by the usual suspects – the installer or remover of the transformer. The smoking gun possibilities are: the tip of a soldering iron, the tip of a Phillips screw driver… or rough handling (dropping or bumping the transformer against something sharp, etc.) with enough force to puncture it to cause such a failure. And finally, we cannot rule out beer as another possibility.
You can now relax. Your tubes and speaker are now ruled out as possible components of interest.
What gets burned out in a transformer that you’re actually replacing?
The magnet wire. When its insulation gets over taxed the fuster-cluck begins as the insulation system of the overall coil progressively losses its integrity (dielectric strength) and begins to arc or burn.
Can you ever rewind a transformer with its original wire?
We certainly wouldn’t do it. When the tires of your car are worn out, do you go out and buy used ones to replace them? Unless you’re a former stockbroker, what’s the point?
Magnet wire is not bare copper wire. There is a micro thin coating of plastic insulation that protects it from shorting. That very thin layer of plastic is susceptible to microscopic spider web-like cracking. And the process of unwinding the magnet wire virtually assures it’s going to get damaged.
Check out the photo of what the magnet wire from your transformer looks like after it was unwound. Does this look like something you’d want to put back in your transformer?
Has any of the machinery used for rewinding changed over the years?
Most of our methods and equipment for rewinding transformers we consider proprietary. So I’m going to stay away from specifics. However, the basic concept of winding equipment hasn’t really changed for over the last 100 years. Today, of course, we see more computerized machines. But we chose to stick with the gold standard of vintage equipment
Aside from ours, I’d be surprised if there is any precision equipment available that is dedicated for the sole purpose of unwinding/rewinding. Most attempts at rewinds today just use run-of-the-mill winding machines that produce, at best, haphazard results.
So if someone gives you a prized “mojo” tranny, do you have the capability of rewinding it exactly the way it was before?
You know I’m not a big believer in mojo. I maintain that all things to do with amps and their respective tone can be easily explained and reproduced, and dare I say it… improved. But yes, we do have the capability. We treat all transformers with the respect and the dignity they deserve. Most people in this business wouldn’t treat these transformers with such reverence. Likewise, they may not have any musical background or an appreciation for electric guitar tone. We’re more than just a transformer company. If the original transformer included magical “fairy dust” or whatever that made it sound unique and desirable, we wouldn’t overlook it or change anything. That’s our promise.
We must be doing something right because we receive mountains of mail, email and phone calls from players all over the world who thank us for giving back (or preserving) their amp’s mojo.
When you begin rewinding, are you using the same wire that was used in the ’50s and ’60s?
That brings up a couple of interesting and important points. First, Mercury is probably the only company in this industry that uses high-purity OFC (oxygen free copper) magnet wire made in here the U.S.A. – which we use exclusively because of its guitar tone (as well as our hi-fi audio) properties. This type of wire is clearly sonically superior and more consistent than the wire that was used in the ’50s and ’60s. Wire technology back then was limited to about half of the temperature and electrical performance of Mercury’s standards. As a result, transformers using our materials last longer, take more abuse, are sonically more revealing, and follow a closer musical path when over driven into harmonics.
The second point is that we, as players, would much prefer the original wire from the ’50s and ’60s to the offshore and south-of-the-border suppliers of magnet wire. We gave them a chance, thinking we’d save some dough for our customers. The tested results yielded dull tone, inconsistent batches with too many instances of insulation breakdowns. Not even up to the standards of the vintage wire. Further, in real life tests of putting amps through their paces, the sonic differences were quite noticeably inferior to the guitar players here at Mercury and the players working for the recording studios here in southern California.
Have you ever seen a negative effect of age on a transformer?
In some cases yes. Sometimes your ears may pick up on affects of transformer aging before you realize what is happening. Dark, dull and fuzzy tones with a general sense of lower output volume.
If anything suffers from aging it will most likely be core. There are two major contributors that cause a negative effect of aging and affect your tone. Before World War II the science of processing iron was not up to snuff. It seemed that it was difficult then to boil out residual carbon from the iron. We are carbon-based life forms that age. We also rely on carbon for dating or aging organic compounds. Even a miniscule amount of carbon left in the older iron causes it to age. As the iron core ages, the magnetic conductivity begins to poop out, slowing the transformer’s responsiveness with increasing losses. The result is less output with only lower mids breaking through.
During WWII there was a shortage of iron for the war effort. So many transformer companies, in order to survive the hard times, made their cores out of soup can sheet metal! Transformers made this way were naturally plagued the wrong kind of iron and harboring plenty of carbon to boot. Do not confuse iron with steel. Finally, when silicon was implemented to help force out the carbon from post war iron, transformer iron became much more stable. Stable enough to out last us all.
Another contributor to transformer aging comes from humidity. Amp owners who live in humid climates have noticed their tone changing over the years. This is especially true if their older amps had transformers built around paper tubes. Paper-bobbins have always run the risk of moisture absorption affecting and changing tone. Conversely, we found that amps built with premium transformers that utilize plastic bobbins weren’t likely to suffer tone degradation via moisture saturation. A couple excellent examples would be the original Partridge and Radiospares transformers from England. With all the fog and rain they experience, these transformers have held up quite well.
Maybe this explains why coating paper in wax was attempted early on? To verify that dew point (humidity) affected output transformer tone, we had transformers from amps made in the ’60s, that had never left the U.K., flown in. They were provided to us by some of the best legendary players their country had to offer. They knew what their amps sounded like originally.
We put their transformers (all with paper bobbins) through a dehumidifying process, then re-sealed them in a generous varnish dip and a full bake. All these guys freaked out and thanked us for giving them their original tone back! And one of the player’s even called with a personal thanks that we had reaffirmed that he had not actually suffered hearing loss! He said that as time passed he noticed less treble tones and a lot less note separation and definition. Note attacks seemed impeded. Other players also had this mistaken belief that their amps were getting too old to play.
Obviously this new transformer won’t be dipped in wax like some of the old experimental ones. What will you use to insulate it?
Well, I wouldn’t call your transformer new. It’s still a 1960. If we had restored a 1960 Corvette for you, does it change the year, make or model? Instead of a fresh coat of paint for the car, your transformer will receive a fresh dip of glorious varnish. A non-flammable sexy coat of see-through clear. Something that may last long enough to pass along to your grandkids.
What can I expect the tonal differences to be between the rewound transformer and the original?
It should sound as good as when it left the showroom floor in 1960.
Your only other option, as far as upgrading the tone, would be to try one of our ToneClones. These are copies taken from some of the finest specimen celebrity-owned and played “pick of the litter” amplifiers. And it’s likely that you’ve heard these transformers in action on your favorite recordings.
Have rewinds come back to you shortly after you’ve sent them out?
On occasion, yes. Installer error happens, and if you don’t find and fix the problem that caused the transformer to blow in the first place, you’re just setting yourself up for a repeat performance.
Another thing that’s fairly common is the use NOS tubes. Usually purchased from eBay. We had a situation once where a customer, after installing his rebuilt transformer, decided to re-tube his amp with 40-year-old American-built originals. As luck would have it one of the NOS tubes shorted and caused a different failure in the newly rebuilt output transformer.
Is a rewind in store for every old transformer, or will they go on forever?
No, not every old transformer will need to be rewound if taken care of properly. Perhaps most may outlast the “Iron Age” of guitar amplifiers which we’re living in now. The push for solid-state technology is tenacious enough to replace tubes/transformer-based amps in the long term (perhaps within the next 50 years?). Tubes may go but they’ll have to pry the transformers from my cold dead fingers before I’ll give them up.
We recently put transformers of all kinds, old and new, to the test by volunteering to help out the flood victims in Nashville. We offer to test and restore any flood damaged guitar amp transformer sent to us free of charge. We encountered some pretty nasty stuff. Yet, less than 5% of them needed to be rewound! (Namely, transformers with paper bobbin insulation, or amps that had been turned on before the transformers were tested.) Some of the transformers that came in were from amps that had been submerged in raw sewage for weeks! The odor was so fowl that we had to air them out, and the staff actually had to draw straws to determine who was going to work on them.
Talk about your shit jobs.
Man, you got that right! Ah, but there’s nothing like the fresh smell of varnish in the morning to help one deal with that challenge. We did manage to extract the moisture and reseal these transformers with varnish. The sacrifices you have to do to help out fellow musicians….
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The voltages in your amplifier can be dangerous. Transformers and chokes are not user serviceable parts. Installation of these components should always be performed by an experienced technician.
The simple ability to use a soldering iron is not enough to qualify a “do it yourself person.” Those who are inexperienced in working with electronic circuits should never attempt to service their amplifier. Household line currents can be deadly!! Transformers, chokes and large filter capacitors can store a dangerous charge for several days or more after the amplifier has been unplugged. Never touch the terminals of such devices without being certain of their charge status. Risk of shock and damage to equipment may result from mishandling and/or improper use of these components. Please use common sense and always think safety first. After all, tone is most enjoyed when you are alive to hear it.
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