drri_mod.txt
[Mods for the Deluxe Reverb Reissue]

From the AMPAGE Tech-Talk BBS:

Name: George Leroy Tirebiter
E-Mail: xxxxxx@xxxxxxxx.net
Date: 1/XX/00 2:21 AM
Subject: Re: 65 Deluxe Rev. RI. Too Bright!

Spencer,
I just finished one these for a friend so I've got some notes on the Deluxe
Reverb RI. The consensus in my neck of the woods is that these RI's are harsh
and too bright and although no one has played through all of them, the three or
five I've seen have followed that script. I've got an actual 'mod' that works
pretty well on these but first things first.

The circuit board that all the pots are mounted to holds the 'bright cap' and a
few other goodies. The bright cap is designated C10 on the circuit board and it
is found between the #2 jack on the Vibrato channel and the volume control.
You can take it out (or disconnect 1 leg) but I prefer putting in a smaller value
like 43 pf or 39 pf. But what will really help this channel is changing the 'slope'
resistor, which is R18 and located around the treble pot. Change it from the
stock 100K to 82K (if it makes the amp too dark for your taste, try a 91K). That
will solve most of your problem.

Now if you're a 'modding kind of guy', you could go on from there and make
these additional changes, but this is just between you and me. If the guys on this
forum find out what kind of heresy we've been talking, Leo himself will
probably come back from the grave to spank me with a leather amp handle (or
maybe Bill Paley??). And who knows what they'll do to you; just for even
thinking about it. Of course, it is your amp, it's not point-to-point, they currently
making lots more and we won't drill any holes, will we?? Oh well, let's get on
with it!

Change the cap C7 from 250pf to 430pf or thereabouts (330pf to 470pf). Some
folks say a silver mica cap is a good idea; it surely isn't a bad idea. Change
both C8 and C9 to .022uf/400volt. My choice would be a good quality cap
(sprague orange drop, mallory) at 600volts. Change R21 (mids resistor) from
6.8K to 10K. It is located next to the bass control. On the big circuit board,
locate C12, a coupling cap, and change this from the stock .022uf to .047uf.
Now take that .022uf you just removed and find C25 on this main circuit board.
Remove the cap (.001uf) and install that .022uf. Alot of LA players who have
these amps are playing this mod. Now I'm not so sure that I'd do this to a BF
DeluxeR. but it seems to help the circuit board model.

If you're after breakup and an overdriven sound then you're done. But if you
want to get a slightly cleaner sound or need more headroom for live
gigging/bigger rooms, then try this:
Open up the filter compartment on the underside of the amp and locate the
10K/1watt that feeds the phase inverter (where a 100k resistor and 82k resistor
meet). Change THAT 10K resistor to a 2.2K/1watt resistor (this is a Leo/Paley
mod). 

You could also install a solid state rectifier. If your amp has as low a B+
voltage as the last RI I saw (405vdc), then this could be a good idea. This
rectifier brought the B+ up to 420vdc. I would recheck the power tube bias if
you go for the SS rect. But only do this SS rect. if you want more clean sound
out of your amp. 

Of course, all this stuff is dependent upon what sound you're after, what kind of
music you play, what type of guitar you use (and pickups) and what sort of
outboard gear you're using. But this will improve these amps and get you
started in the right direction.

Be careful with the circuit board, it is fragile! 
Good luck,
George