My Fender Pro Reverb Amp's Rebirth

I have an old fender silverface pro reverb.  It's a non master volume model.  I loved the amp when I first got it several years ago.  Such great reverb, loud enough to stay clean with my hard hitting drummer at the time.  As time goes on we always find things that we don't like or things that need improvement.  I had done the blackface mod to the amp a while back, and while that was a huge improvement, I decided that I needed more.  I mean I have two channels, one of which NEVER got used.  There really isnt much point to having two identical amp channels that are out of phase with each other, especially when the normal channel doesnt have reverb.  I decided I wanted to make one channel different, and keep one the same.  I am in the process of putting reverb and tremolo on both channels.  I made the currrent reverb channel my modded channel and kept the normal channel mostly the same.  I also completely overhauled the amp- So far I have...

1.) replaced all the coupling caps and tone caps with Orange Drop 225 Polyester film caps- these are kind of like the mallory 150m's, different than the overly harsh orange drop 715's.  The coupling caps drift over time and my fender didnt have the revered "blue molded" caps... they are blue though.  This made a ridiculously huge improvement in the response and clarity of my amp.  This alone made the breakup sound much better

2.) I then took a cue from jerry garcia's modified twin reverb preamp that he used over the years and replaced all of the cathode bypass capacitors and resistors in parallel with them to some NOS sprague 150d Tanatulum caps, I used PRP modern american made military spec metal film resistors in paralell.  This really changed the 'quickness' of the amp, sounds like I have less "sag".  It's more responsive and touch sensitive with these caps.  I think they may be adding noise though (the parts experiments are not done though- These are all my first choices) I also have a solid state rectifier to replace the tube rectifier in the pro reverb on the way.

3.) replaced all plate resistors with PRP metal film resistors- these are high quality low noise resistors, made for audio.  These really brought down the noise in the amp.  really bumped up the clarity in doing so.  These really do sound different from the carbon comps.  More HiFI, brighter maybe, cleaner, but not sterile at all.  These resistors are the modern version of the Dale rn65 or RN70 series.  Non inductive, non magnetic, and super precise.

4.) the values of the tone caps- I changed bass cap to .022uf and the mid cap to .022uf and the treble cap to a sivler mica 390pf.  This is for the lead  channel- it really brought up the mids in the normally bass and treble heavy fender amp.  I also increased the plate resistors using takman hi fidelity carbon film resistors.  audiophile stuff.  this increase to 150k caused a nice gain increase in that channel.  it starts to break up around 5 on the dial- where as it used to be about 7-8.  Very nice sounding.  the takman carbon films warmed up the overdrive instead of the metal film PRP's

5.) Changed grid resistors on power tubes to 2 watt non flammable ones.

6.) the pro doesnt have a mid range knob- I am in the process of adding one

7.) also adding a negative feedback knob... this will allow the amp to go from stock to sounding much meaner and aggressive.

8.) new reverb tank- reverb tanks wear out- mine just stopped sounding good, got noisier and metallic sounding.  I tried messing with the reverb circuit components, and it helped, but not enough.  The new accutronics tank sounds absolutely amazing!  classic fender

I am also waiting on parts to change out the filter caps.  And I may end up putting some nicer heyboer transformers in the amp eventually.  Some other easy modifcations included using 12ax7 tube in the phase inverter position and a 12at7 in v1 of my preamp.  This gives the amp more power tube gain and saturation and less preamp breakup.  The 12at7 sounds bettter when breaking up too.  Fender amps are not made for preamp distortion so I really try to keep that down.  I did a number of component value changes that minorly tweak the amp here and there.  It's a lot like cooking. You dont wanna go in there and use a ton of one ingredient- a little dash of lime to even out the sugar, a little salt to bring it out, but not too much.  Everyday I am changing values of parts- trying different types of parts- different material compositions.  trying to tune this amp perfectly to my dream amp.  I will be adding external bias testing points.  Maybe add tone and dwell knobs for my reverb.  I'm even contemplating adding a tube effects loop.  These silverface pro reverbs can still be had for realtively inexpensive prices.  I bought mine for $700- thats $700 for a 45 watt, hand wired, 2x12 tube amp that will last longer than you will!  Put a little elbow grease in them, and you have a boutique amp for under a grand!  Really amazing what you can do with these things.  You can even really get them to distort heavily- I may try a "Mesa Mark IIc" mod for the normal channel I've found by another fellow experimenter.  These ideas are just the tip of the iceberg, I havent even gotten into adding a tone stack bypass, or extra tube gain stages.  I think going too far has its problems- the best way is to do minor tasteful tweaks, using high quality parts, and you can get these things sounding better than the best blackface amps. I'll post soundclips soon!

Orange Drops (big orange things) PRP resistors (small red tubular things) NOS sprague 150d caps (silver tubulars) and silver mica cap (the little brown thing) Having new quality parts really brings the amp back to spec.  how it was meant to sound before all those old components got dried up, burnt out and out of tolerance.  it's crazy how good I can now make these amps sound!