Re: Small Harp Amp Princeton Reverb

["James D Rossen and Dina Janzen" <dlj@xxxxxx>]

I have modified my 1970 PR fairly extensively (all easily reversed).   Why mod a
great amp?  First, I thought that the breakup was a bit harsh and bright.  Also,
I am an amp fiddler- I can't help it.   Most useful mods in my mind are-

Speaker- I favor the Weber ceramic C10N over the alnicos I have tried. More of a
horn-y honk then a rasp, and much louder.  My C10Ns are in another amp at
present, and the Weber P10R in the PR sounds fine also, but very different.   I
may be in the minority in favoring these ceramics over alnicos.   But I have the
Weber C10N H dust cap speakers in a 2 x 10 combo cab, and every amp I play into
this cab sounds killer.  I am thinking about trying other sizes of C-xx-N in
other amps- anyone try a C15N or C12N?   (I don't like all ceramics, the Weber
C10Q is too bright).

Reverb- replacement of two circuit components makes the reverb much darker and
warmer- good for harp.  A short delay tank does what you'd anticipate and sounds
great.

Coupling caps-  High value interstage coupling caps help pass more low end.

Phase inverter mod- fairly involved, reduces the distortion at this stage, which
is sort of harsh, and allows more power tube distortion (at least with guitar).
Don't know if this is good for all harp players, but I like it.

Most of the circuit mods are easy to do as the eyelet board is well designed.

HOWEVER- CAREFUL TECHNIQUE AND SOME UNDERSTANDING OF WHERE THE HIGH VOLTAGES ARE
IN THE AMP IS NEEDED TO AVOID BAD SHOCKS.  THIS AMP RUNS IN EXCESS OF 300 V IN
THE POWER SUPPLY.  THE FILTER CAPS CAN RETAIN CHARGE AFTER THE AMP IS TURNED OFF
AND UNPLUGGED.


Jim R




 If I had more time, I'd get into some more details of
> mods, but I got two Princeton Reverbs on my bench as I type this e-mail that I
> have to get working on.  Hey Jim R. can you help me out here!?!?! :-)
>
> Regards,
> Don D.