[RiverRat]

Does anyone have schematics and diagrams for the Blaster, Buffer, and modified Twin... I lost mine in a recent hard drive crash.

PLEASE, PLEASE, PLEASE... DO NOT SAY "Go ask Waldo." I'd rather crawl headfirst into a rattlesnakes den.

[Jon S.]

Re: the Twin mods, here's what I saved with attribution to their sources as noted at the time, ALL OF WHICH WERE IN THE PUBLIC DOMAIN WHEN I SAVED THEM (so, please, everyone, no crocodile tears):

As for potential TR mods, if you do some internet word searches, you'll find comments like these in the public domain that may assist you. Note that I have no relationship or affiliation with any of the cited sources for the info. that follows. I'm merely letting you know who I saw posted the info. in case you want to take that into account in determining its usefulness to you:

* I just saw on a respected sources website that Jerry's Twin had .022's in the tonestack instead of the normal .1 and .047. (Imagined Days)

* .022s in the mids will keep more mids around than some of the other higher value capacitors commonly used in fender amps, and .022 in the bass will cause the bass frequencies to drop off at a higher value and lose a lot more overall bass than the .1. So, theoretically, .022s seem to make sense for jerry (more bass cut and less mid scoop) (Stevo123)

* It is by no means a secret mod, others have done it. using the duncan tonestack calculator, and the known jerry twin settings, show a pretty identical curve between the stock values and the .022uFs. the difference being the sharper bass rolloff with the .022uF's. (Mike Wald)

* Just got my twin back from the tech with all the healy mods done and played a farm gig over the weekend. YOW! Talk about clean power and clear highs and lows. (JB Arnold)

* Let me suggest a place to start: First, in addition to changing all of the caps, you will want to change all of the plate resistors for non-inductive metal film versions. Also change all of the cathode resistors and use tantalum capacitors for the bypass caps (I use military grade axial lead versions). This, especially for steel, will greatly improve the high frequencies yielding the pure and clearer bell like tones. (JB Arnold claiming to be quoting Healy)

* I've done most of the mod that JB quoted except for the non-inductive metal film plate resistors. That's next. The other mods were amazing. I've never heard a Twin so open and sweet and clear and hi-fi before. The steel just sings thru it. (Brad Sarno)

* Maybe you’ve moved on from your Silverface twin project, but I still want to chime in. I’ve got the same amp (late 73 twin reverb with all rca tubes. Mine doesn’t seem to have the power tube suppression caps either) and I’ve done a lot of the preamp mods mentioned in this forum and elsewhere about how to achieve Jerry tone. I’ll give you a little rundown of what I’ve done, and encourage you to dive in:

- changed the tone stack .022,.022, and 250pf - Sprague 225p and silver mica

- dale metal film plate resistors, RN series

- Sprague tantalum 150 series cathode bypass caps, 22uf

- black-faced the phase inverter and bias pot with dale metal film resistors, xicon metalized polypropylene caps - I like these in the phase inverter over the orange drops: responsive, 3-dimensional and textured

- changed the phase inverter input cap to .oo27 Sprague 225p - fattened up the tone just enough

- disassembled the master volume circuit, and disengaged the tremolo

- after lifting the wire to the Tremolo pot, I changed the cap on the right of the phase inverter from .1 to .047 (Sprague 715p) this tightened up the bottom end in a necessary way - I don’t see too many people talking about this but it seems important to my ears

- I changed out a few capacitors here and there to 225p orange. Drops

- AND just today I swapped out the reverb driver resistor on v4 from 850 ohm to 2200k metal film and found the sonic edge I’d been looking for. It added a bit of gain and breakup overall and a quality to the reverb that is just killer. I feel I’m almost there - think early spring ‘78 (Pointclear)

Jerry’s Twin had .022's in the tonestack instead of the normal .1 and .047. .022s in the mids will keep more mids around than some of the other higher value capacitors commonly used in fender amps, and .022 in the bass will cause the bass frequencies to drop off at a higher value and lose a lot more overall bass than the .1. So, .022s make sense for Jerry tone (more bass cut and less mid scoop). I.e., using the Duncan tonestack calculator and the known jerry twin settings, you can show a pretty identical curve between the stock values and the .022uFs. the difference being the sharper bass rolloff with the .022uF's.

Some people also make these cap changes. In addition to changing all of the caps, you can change all of the plate resistors for non-inductive metal film versions. Also consider changing all of the cathode resistors and use tantalum capacitors for the bypass caps (use military grade axial lead versions). Thiswill greatly the high frequencies yielding the pure and clearer bell like tones.
Following are additional notes I’ve taken from reading others’ posts on their Jerry tone TR preamp mods:

- change the tone stack .022,.022, and 250pf - Sprague 225p and silver mica

- substitute dale metal film plate resistors, RN series

- substitute Sprague tantalum 150 series cathode bypass caps, 22uf

- black-faced the phase inverter and bias pot with dale metal film resistors, xicon metalized polypropylene caps (some prefer these in the phase inverter over the orange drops)

- changed the phase inverter input cap to .0027 Sprague 225p

[Jon S.]

And, despite what some may claim or want you to believe, the Blaster and Buffer are both simple circuits which have also been in the public domain for decades. Do internet searches and you'll find them.