B
Bruce Morgen
The basic mods are done and working
very nicely -- a little advice, if
you would:
1. Is it worth changing the value of
R11? What's in there is much higher
than Leo had it, but then again Leo
used a lower-gain V1A triode and
shared the cathode circuit between
two channels, and if the diagrams are
accurate the G40V has less than 2VDC
on V1A's cathode as contrasted to Leo
with 2.5VDC.
2. Could you analyze V1B's circuit
and recommend some sane values for
its cathode resistor and cap,
assuming a 12AU7 as that triode?
Others have removed C9 entirely,
fwiw. With that stage switched
in, in addition to a fuktonne of
extra gain, there seems to be a
lot of what I hear as upper
midrange emphasis, e.g. "string
speak" when a finger slides along
a wound string is obtrusively loud
to my ear and I'd like to tame
that some.
3. I'm not sure of the function of
C13, coming off the tone stack and
right to ground -- this is another
cap that others have simply removed.
Keep in mind that I have decreased
the tone stack treble cap to 270pF
and increased the slope resistor to
52k, am still finding the treble
control pretty ineffective (bass
control is much improved, btw), and
wouldn't mind the amp being just a
tad brighter, especially in its new
"Tweed" mode.
Any and all help greatly appreciated
-- thanks in advance!
very nicely -- a little advice, if
you would:
1. Is it worth changing the value of
R11? What's in there is much higher
than Leo had it, but then again Leo
used a lower-gain V1A triode and
shared the cathode circuit between
two channels, and if the diagrams are
accurate the G40V has less than 2VDC
on V1A's cathode as contrasted to Leo
with 2.5VDC.
2. Could you analyze V1B's circuit
and recommend some sane values for
its cathode resistor and cap,
assuming a 12AU7 as that triode?
Others have removed C9 entirely,
fwiw. With that stage switched
in, in addition to a fuktonne of
extra gain, there seems to be a
lot of what I hear as upper
midrange emphasis, e.g. "string
speak" when a finger slides along
a wound string is obtrusively loud
to my ear and I'd like to tame
that some.
3. I'm not sure of the function of
C13, coming off the tone stack and
right to ground -- this is another
cap that others have simply removed.
Keep in mind that I have decreased
the tone stack treble cap to 270pF
and increased the slope resistor to
52k, am still finding the treble
control pretty ineffective (bass
control is much improved, btw), and
wouldn't mind the amp being just a
tad brighter, especially in its new
"Tweed" mode.
Any and all help greatly appreciated
-- thanks in advance!