ASK AMP MAN
JEFF BOBER
Peavey Classic 50/410 Combo
Jeff, Hello Dan,
Your answers to questions in Premier Guitar Thanks for reading Premier Guitar and also my
have left me 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
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
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.
has a fresh set of tubes and should sound
great once the cause has been found and the
problem remedied.
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 In order to clean the sockets, obtain some
start looking to get this fixed I would really electrical contact cleaner that does not
appreciate your advice. I just looked at the contain lubricant. Remove the tube, spray
web site for Mercury Magnetics upgrades a decent amount of cleaner into the socket
and was wondering if you had any experi- and cycle the tube in and out of the socket
ence with their claims. Sounds good, but is it
worth it? socket and move on to the next socket.
When all the sockets have been
Dan 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.
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.
If not, I would next
-
remember, however, is
that a new preamp tube
can also produce different types of mechanical
or microphonic noises.
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
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.
If your original symptom
has been eliminated but
the amp is now produc-
ing 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
I hope that helps you restore your Classic.
Jeff Bober
Co-Founder and Senior Design Engineer
Budda Amplification
jeffb@budda.com or www.budda.com
©2008 Jeff Bober
