Fig . 2
Fig . 3
multiple smaller values . I would start with a 47 pF and work up to a 100 pF , a 220 pF , or even a 470 pF to see what suits you best . Of course , if you play with the preamp volume on 10 , this is all moot , since the capacitor is electrically out of the circuit at that point . A nice feature here might be to have this cap switchable using a push-pull pot for the preamp control .
This way you could tailor the amp depending on your guitar choice .
If the amp is still too bright , the next place I would go would be the high-pass cap ( C102 ) across the 470k resistor that feeds the signal to the preamp control ( Fig . 2 ). This is typically a 470 pF cap and can simply be lifted from one side of this resistor . If you then like the amp , you can either completely remove the cap or install a push-pull pot for the master volume control and make this capacitor switchable as well . It ’ s always good to have choices .
Less gain , more pain ? The above two modifications deal with components that are typically not board mounted . In these early amps , they are usually connected directly to the input jack or preamp volume pot , making for easy access and modification .
There is one more component that you may want to consider experimenting with . It is the cathode bypass cap ( C2 ) in the first gain stage ( Fig . 3 ). The value of this cap is typically 0.68 µ F and is connected across the 2.7k cathode resistor of V1 . This helps the tube amplify more of the higher frequencies , but removing this , however , removes some gain and tends to leave the amp a bit lifeless .
My suggestion would be to parallel this with a larger cap . This won ’ t decrease the high-frequency amplification , but rather raise the full-frequency amplification . It will give you the relative effect of less treble , while increasing the gain a bit overall . I would start with maybe a 4.7 µ F 25V DC cap and see how you like it . You can use a pair of alligator leads here . Just be sure that the positive (+) side of the capacitor is toward the tube . You can go up in value from there to , say , a 10 µ F , 25 µ F , 50 µ F , even a 100 µ F to see if any of these are to your liking . If so , simply solder it across the 0.68 µ F cap , being aware of the polarity .
Well , there you have it . One or more of those modifications should get your amp to where you have a useable combination again . Glad I could help with the Taming of the Shrill .
JEFF BOBER is one of the godfathers of the low-wattage amp revolution . He co-founded and was originally the principal designer for Budda Amplification , though he launched EAST Amplification ( eastamplification . com ) in 2010 . You can catch his podcasts at ampsandaxescast . com or email him at pgampman @ gmail . com .
premierguitar . com PREMIER GUITAR SEPTEMBER 2016 135
Fig. 2
Fig. 3
multiple smaller values. I would start with
a 47 pF and work up to a 100 pF, a 220
pF, or even a 470 pF to see what suits
you best. Of course, if you play with the
preamp volume on 10, this is all moot,
since the capacitor is electrically out of the
circuit at that point. A nice feature here
might be to have this cap switchable using
a push-pull pot for the preamp control.
premierguitar.com
This way you could tailor the amp
depending on your guitar choice.
If the amp is still too bright, the next
place I would go would be the high-pass
cap (C102) across the 470k resistor that
feeds the signal to the preamp control
(Fig. 2). This is typically a 470 pF cap and
can simply be lifted from one side of this
resistor. If you then like the amp, you can
either completely remove the cap or install
a push-pull pot for the master volume
control and make this capacitor switchable
as well. It’s always good to have choices.
Less gain, more pain? The above two
modifications deal with components that
are typically not board mounted. In these
early amps, they are usually connected
directly to the input jack or preamp
volume pot, making for easy access and
modification.
There is one more component that
you may want to consider experimenting
with. It is the cathode bypass cap (C2)
in the first gain stage (Fig. 3). The value
of this cap is typically 0.68 µF and is
connected across the 2.7k cathode resistor
of V1. This helps the tube amplify more
of the higher frequencies, but removing
this, however, removes some gain and
tends to leave the amp a bit lifeless.
My suggestion would be to parallel
this with a larger cap. This won’t decrease
the high-frequency amplification,
but rather raise the full-frequency
amplification. It will give you the relative
effect of less treble, while increasing the
gain a bit overall. I would start with
maybe a 4.7 µF 25V DC cap and see
how you like it. You can use a pair of
alligator leads here. Just be sure that the
positive (+) side of the capacitor is toward
the tube. You can go up in value from
there to, say, a 10 µF, 25 µF, 50 µF, even
a 100 µF to see if any of these are to your
liking. If so, simply solder it across the
0.68 µF cap, being aware of the polarity.
Well, there you have it. One or
more of those modifications should get
your amp to where you have a useable
combination again. Glad I could help
with the Taming of the Shrill.
JEFF BOBER is one of the
godfathers of the low-wattage amp
revolution. He co-founded and was
originally the principal designer
for Budda Amplification, though
he launched EAST Amplification
(eastamplification.com) in 2010.
You can catch his podcasts at
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