Add a Real Choke

I’m a player from Los Angeles. Even though I endorse companies like Framus and Brunetti amps, who both make fine equipment, I still rely on Marshalls for some of my favorite tones.

Last month I went on a quest—how can I make my “road-dog” amp, a Marshall JCM DSL 2000, play like my vintage 30+ year old Plexi (which stays home, of course!)?

Well, first I got a tech to change a couple little things: resistors out from the volume pot, a couple of changes with the EQ resistor’s values, etc. This made a bit of difference. Then I played with a variation of power and preamp tubes, from different companies (GT, JJ and Tesla) until I found the combination I liked best. This made a perhaps 25% difference. I was happy, but still searching for that missing ingredient because the Plexi had… well, more of everything, including more power, more clarity, faster response and fuller overall frequency. So, I kept fishing around on the web and by chance hit upon a review for Mercury replacement transformers.

As luck would have it Mercury is located 5 minutes from my home! I thought I had nothing to lose by replacing the transformers since it’s usually a fast and easy tech operation, so I went to see them.

Along with their technical knowledge, what struck me instantly was their level of care and enthusiasm. Mercury’s Sergio Hamernik explained that I could do more than upgrade the existing power and out-put trannies, such as add a real choke to the circuit, like the original Marshalls(the stock DSL has a cheapy resistor instead of a choke).

Although Mercury had something special in mind, I had a gig in a couple of days, so we decided to only replace the output tranny (OT)—then finish the job later. Not all transformers are the same within any model (or year) of amplifier, and in many cases there are radical differences. Mercury makes a particularly outstanding drop-in output that would help the JCM’s sound. Although it was a temporary “patch”this change gave me the chance to feel, let me repeat, f-e-e-l the amp at my gig, and I was positively surprised by the how it reacted and sounded. Simply stated, the improvement with the feel and tone was 50%. After the gig Mercury went to work on my amp by liter-ally re-engineering new power and output transformers specifically for the DSL. The power transformer(PT) utilizes their new “SuperStack” technology (it’s huge and looks like a skyscraper in there!) that completely eliminated the amp’s tendency to overheat! They also modified the circuit by adding a choke. The final result was nothing short of a revelation! The amp has more power, better tone, faster response, wide palette of frequencies… it has more of everything!


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