Jeff,
Your answers to questions in Premier Guitar have left
me to believe that you might know what I am hearing when I
use my Peavey Classic 50/410 combo. I love the tone
that I get, but there seems to be an intermittent swirl
sound that happens while I am playing. It doesn't affect the
amped signal, but is in the background. Sort of like a
spacey, swishing hum from a bad ground. I have taken a
mirror and tried to watch the tubes to see if one is having
a fit and have seen nothing. I want to get the clean sound
and not have that underlying noise. It doesn’t matter if I
am on channel one or two, have reverb on or off, in bright
or normal channel. I have it just through the combo
or with the 410 extension cabinet. Also here in
Central Illinois, I don’t know of any good techs to take it
to for repair. If you could give me an idea what it is that
is wrong and where to start looking to get this fixed I
would really appreciate your advice.
I just looked at the
web site for Mercury Magnetics
upgrades and was wondering if you had any experience
with their claims. Sounds good, but is it worth it?
-- Dan
Hello Dan,
Thanks for reading Premier Guitar and also my
"Ask Amp Man" column. Glad you enjoy it.
There are a couple of possible causes for such a symptom. I
would say the first, and most easily remedied, would be a
faulty tube. Many different types of noises can come from
tubes, none of which could be visually determined. The first
thing I would recommend would be to clean the sockets and
replace the EL84 output tubes in the amp. These tubes take
the most beating and should be replaced more frequently than
the preamp tubes. You did not mention the last time you had
done this, but a good rule of thumb nowadays is six months
to two years, depending on how often and how loud you play.
In order to clean the sockets, obtain some electrical
contact cleaner that does not contain lubricant. Remove the
tube, spray a decent amount of cleaner into the socket and
cycle the tube in and out of the socket six to ten times.
Leave the tube out of the socket and move on to the next
socket. When all the sockets have been cleaned, leave the
tubes out and give the sockets ample time for the cleaner to
evaporate -- maybe fifteen to twenty minutes. Install the
new tubes, fire up the amp and see if this has cured the
symptom. If not, I would next replace the 12AX7 preamp
tubes. One thing to remember, however, is that a new preamp
tube can also produce different types of mechanical or
microphonic noises. If your original symptom has been
eliminated but the amp is now producing a metallic ringing
or starts feeding back, move around the location of the
preamp tubes to see if you can place the offending tube in a
less sensitive location. If neither of these alleviates the
symptom, at least the amp has a fresh set of tubes and
should sound great once the cause has been found and the
problem remedied.
To further explore the possible causes, I posed your
question to John, an engineer friend of mine at Peavey,
and I believe we may have another possible answer for you.
The Classic 50 uses a wire connecting the preamp
circuit board to the output tube circuit board, which
provides the ground connection to the output board. This
should be a black wire utilizing a white plastic connector
approximately one inch long and attached to J74 on the
output board (if marked). The recommended way to repair this
potential cause of the problem is to upgrade the connection
by removing the connector, stripping the wire and soldering
the wire directly to the pin on the circuit board. This will
provide the best, most reliable ground connection, without
the worry of oxidized or intermittent connectors. This may
be a larger task than most players are capable of and
servicing tube amps should not be undertaken by anyone
unfamiliar with the hazards, so find an experienced service
technician to perform this kind of work. Regarding your
question of such a technician in Central Illinois, I
personally do not know anyone in that area. However, I'm
sure if you inquired in any of the various gear forums you
would find someone who is trusted.
To the last part of
your question concerning the
Mercury Magnetics upgrades: I have used their
replacement transformers in the past and they definitely
make a wonderful product. While I have not had the
opportunity to install one of their recent upgrade
kits, I have heard from players who have had the
opportunity to compare stock and upgraded amps
side by side, and they tell me the difference is quite
noticeable. One even found it hard to believe they were the
same model amps -- so I'd have to say that if you have a
discerning ear, it may be a worthwhile investment for you. I
hope that helps you restore your Classic.
Jeff
Bober
Co-Founder and Senior Design Engineer -- Budda
Amplification
jeffb@budda.com
www.Budda.com
Source: Premier Guitar
Edition: March 2009
©2008 Jeff Bober