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From: "Steven Rousseau"
Date: Fri, 16 Oct 1998 10:23:09 -0400
Subject: 6V6 in a Music Man

The last Music Man amp I worked on had an interesting feature, a HIGH and
LOW power switch.

Unlike a lot of other amps, the Music Man's way of reducing output power
was to reduce the high voltage supply going to the output tubes. If your
amp has one of these HIGH / LOW power switches, then you are in luck. 6V6
and 6L6 power tubes have the same pin out, 6V6 just do not handle the
voltages and power that a 6L6 can.

Remove the 6L6 power tubes, and measure the DC voltage in hole number 3 of
a power tube socket.
** WARNING ** You can really zap / kill yourself if you don't know what you
are doing, you be the judge.

If, with the amp on and set to LOW power, you read 425 V dc or less then you
can attempt to install some SOVTEK 6V6 tubes (up to 450 Vdc with NOS
tubes). You probably will need to re-bias the amp, in the mean time just
make sure the 6V6 tube plates do not glow red while the amp is just idling.
Set the bias so each 6V6 power tube passes about 6 to 8 Watts RMS while at
idle.

Watch out though, if you accidentally flip the switch to HIGH power, you are
probably in for an expensive light and smoke show. On high power, the
voltage is above 550 Vdc.

I installed some 6V6 into my blackface Bassman amp a few years ago. I had
to install a power reducing device to get the plate voltages down to 420 V
dc. The amp sounded pretty good, with about half the output power of 6L6
tubes.

Recently, I converted the same amp to run class A with 6L6 tubes. Power
output is half of what you get when running in class AB, the sound is
really nice, (harp and guitar) and good 6L6 tubes are easier to find then
good 6V6.

If you are going to bring your amp in to a tech, then consider the class A
mod. You can even set up the amp to run either class A or class AB with a
flick of a switch. I did this mod to my Bassman reissue and I use both
settings all the time.

Regards... Steve Rousseau

P.S. Fender Twin owners can try this trick to. If you have access to some
nice New Old Stock (NOS) 6V6 tubes,
then try replacing the 6L6 with a quartet of 6V6. Power output is reduced
by about half and the tone is quite interesting. Just make sure the plate
voltages are below 450 Vdc. The bias will have to be re-adjusted.