Re: Smicz TADS to tame a 59 Bassman RI?

Chris Hammond wrote:

> I had an amp tech add a potentiometer which varied the voltage applied to
> the phase inverter tube on my Bassman RI.  This works great to give you fat
> tone on the bassman at low volumes.  I am not sure of the circuit (maybe
> someone on the list can enlighten us)

It's called a pre-phase inverter master volume and is indeed a quick and easy
way to add a master volume as long as you have a suitable place to put the
potentiometer.  Just installed one recently on a Princeton Reverb.  IMO it
doesn't work well if you plan on over attenuating the overall volume, that is
running the volume say less than half.  Below that the sound gets too muddy but
if you just keep it slightly attenuated it does allow you to dial in a nice fat
crunch at a somewhat lower volume.  Post PI master volumes are better and have a
more even overall response but are much more complicated and difficult to
install, requiring several additional capacitors, resistors, a dual ganged pot
and a place to install all of it on the circuit board.  The pre PI master volume
only requires a 1 meg pot and a short length of suitable wire, you simply
replace the 1 meg grid leak resistor on the input grid of the phase inverter
with the 1 meg pot, not perfect but an easy mod.

Don D.

> The mod was very cheap and
> compeletly reversible.  He put the Pot right in one of the speaker
> connectors on the chassis.  The charge was about $30 including labor.
> >From: "M. N." <mnessmith@xxxxxxxxxxx>
> >Reply-To: harp-l@xxxxxxxxxx
> >To: harp-l@xxxxxxxxxx
> >Subject: Smicz TADS to tame a 59 Bassman RI?
> >Date: Tue, 07 Jan 2003 19:54:34 +0000
> >
> >
> >Just wondering if anyone on list has tried using TADS from Smicz
> >Amplification as a way to throttle down the power in your 59 Bassman RI or
> >other high-power amp. Here's the description from
> >"Many of us own great amps that are WAY TOO LOUD for non-stage situations.
> >We've all annoyed loved ones and neighbors trying to let the power tubes in
> >our amps get a workout, and most of us have flirted with permanent ear
> >damage or met local law enforcement personnel in the process. Most players
> >don't realize that 3-5 watts can be surprisingly loud for home practice
> >situations. ... Our TADs are direct replacements for your amp's higher
> >wattage power tubes. A pair of TADs will bring your beloved 50-watt Plexi
> >down to a very manageable 3-4 watts. The same is true for that fine
> >sounding Blackface Super. Simply replace your output tubes with the correct
> >TADs and away you go. There is no adjustment or rebiasing needed. Finally,
> >power tube saturation at reasonable volumes."
> >A '59 Bassman RI will require a pair of TAD-2HVs, which runs $135 with
> >shipping in the U.S. Not cheap, but perhaps a good way to get fat tone at
> >lower volumes from this amp.
> >Curious,
> >MN
> >
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