Gear How-To: Quick Reversible Mods to the Blackface Fender Pro Reverb.

http://fenderguru.com/amps/pro-reverb/

 

So that’s a good page for some mods, some more invasive than others.  Well, I’m not into amp invasion, so I tried two of the easiest reversible mods – Tube Swapping, and Normal Channel Reverb Control.

 

Back in my audiophile days, we called it tube rolling.  The first step is to know what each tube socket does, and in what order.  If you’re looking at the back of the amp, read it from right to left, smallest tube to biggest tube.  Again, from the Right:

 

  • V1 12ax7 = Preamp normal channel
  • V2 12ax7 = Preamp vibrato channel
  • V3 12at7 = Reverb send
  • V4 12ax7 = 1/2 Reverb recovery and 1/2 gain stage for vibrato channel
  • V5 12ax7 = Vibrato
  • V6 12at7 = Phase inverter
  • V7 6L6 = Power tube #1
  • V8 6L6 = Power tube #2
  • V9 GZ34 = Rectifier tube

Check the link above for the blow by blow, but now the amp has this:

  • V1 12ax7 = Preamp normal channel for the Reverb Output
  • V2 12AY7 = Preamp vibrato channel
  • V3 12AU7 = Reverb send
  • V4 12ax7 = 1/2 Reverb recovery and 1/2 gain stage for vibrato channel
  • V5 12ax7 = Vibrato
  • V6 5751 = Phase inverter (the 5751 is like a fancy 12AX7)
  • V7 6L6 = Power tube #1
  • V8 6L6 = Power tube #2
  • V9 GZ34 = Rectifier tube

It gets me in a great sweet spot where the note “round off” and the strength of the vibrato doesn’t get drowned out.

 

The second mod is running the Reverb Output to the front of the amp to the first Normal Channel.

img_3385

As you can see, the RCA that usually goes into the “Reverb Output” is now hooked up to a Grado extension cord, which leads to the front:

 

img_3386

So instead of having just one knob that works in the front called “reverb” (which no longer works) that used to just control the amount of volume the reverb had, you now have a whole channel dedicated to the reverb – yes, all those controls work!  You can use the Bright switch, both the Treble and Bass tone controls, and the Volume acts like the old Reverb knob did – controls the reverb volume.

 

What’s great about this is that I used to have some treble hiss when I used the reverb too loudly.  Now I can crank up the reverb but dial out the hiss by disengaging the Bright switch and rolling off the treble and cranking the bass.  The tone of the main signal doesn’t seem to be affect much, and now there’s no hiss!  Any tone compensation can still be done by using all the controls on the Vibrato Channel, where my guitar is plugged in, like so:

 

img_3389

Another plus is now that the amp is totally dead silent, I can crank it even louder – and the sweep up is more gradual since the tube rolling results in the sweet spot really being spread out from 2 up to 8 in my opinion.  Don’t forget the really strong vibrato throb coming through now, plus it’s not as choppy due to the rounded notes.

 

What a great easy way to get this amp dialed in – plus it’s all reversible if needed!  Man, my 1984 Gibson ES-335 Dot sounds sweet through this.  I was thinking of getting the pots changed out to 500k, but right now it’s got such a great vintagey synergy with this amp, I’m not budging.  That’s including the clean tones!

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2 thoughts on “Gear How-To: Quick Reversible Mods to the Blackface Fender Pro Reverb.

    1. Hi, I remember that Chandler! Sounded great with a cab with 2X10s as i recall. Right now I’m happy going basic with one marshall and one fender, but if things change I’ll reach out thanks!

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