From mvanditt–(at)–cm.org Wed Nov 19 22:41:41 CST 1997
Article: 72442 of alt.guitar.amps
From: mvanditt–(at)–cm.org
Subject: Beefing up a Tweed Champ or Princeton
Date: Wed, 19 Nov 1997 16:12:41 -0600
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Hey Everybody,
I just finished building a homebrewed Tweed 5F2A Princeton style amp, and
would like to share a little insight on to how add some beef to any Tweed
Champ/Princeton circuit that uses 12AX7 preamp tubes. First, and
foremost, add a 22uf/50 cathode bypass cap to the second preamp stage.
This cap will increase gain by 3db on frequencies above 4.8hz. This mod
will push you into the cranked plexi level of gain on volume settings
above 6 (i.e., the amp will sustain and feedback).
Additionally, some of the Tweed circuits (5F1 Champ and 5F2 Princeton
come to mind) have no cathode bypass cap on the first gain stage.
Bypassing the 1.5K cathode resistor with a 22uf/50v will also have the
effect of increasing gain, on this stage, by 3db on frequencies above
4.8hz.
If you want that hard-edged bright Marshall tone, replace the 1.5K
cathode resistor, on the first gain stage, with a 2.7K resistor, and use
a .68uf plastic cap as the bypass cap. This mod will give you a gain and
increase of 3db on frequencies above 86.7hz. The resulting sound will be
much brighter and tighter with a harder-edged crunch.
Mark
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