Pushing V2 harder within older fenders. Pre-amp clipping mod?

[Leo_Gnardo]

It's a SF and have no plans to ever sell so why not make it custom for my needs. Plus it has made for such a great learning tool.

Won't get any complaint from me. I confess to having drilled up lots of SF's. Not so much recently. But there is a Dual Showman Reverb lurking outside my workshop room door. Its owner already had me pulverize one for him & wants the same done to this one. One of these days... soon come!

[pdf64]

To me, most regular Fender pre-amps overdrive just fine, apart from the harsh clipping from the reverb driver V3 being pushed into grid conduction, chopping off the top part of the wave at V2b plate when it gets above ~8V peak.
The SFs with master volume have the V3 cathode bypass removed; my guess is that Fender identified that's where the problem was, but it wasn't a total fix.
A 1M trimmer used as a dwell control pot, and high value grid stoppers (eg 100k) on V3, seem to work better.

[TheTinMan]

My 2 cents: I put a crossline post-phase inverter master volume in a Princeton Reverb and hated it. Yes, it lets you turn up the preamp volume with less power tube distortion. However, distortion in that portion of the preamp is not sweet to my ears and there was a distinct muddiness by the time the PPIMV was turned down enough to make a difference.

You might try a crossline PPIMV as a quickie experiment; however, it's the worst variant of master volume in my experience (which is limited).

Chip

[pdf64]

I put a crossline post-phase inverter master volume in a Princeton Reverb and hated it

I doubt that you would find many advocates for a crossline / type 3 master volume on a cathodyne.
Master volumes after the phase splitter are almost universally used with an LTP.
Cathodynes have a rep for poor behaviour when overdriven; in a regular NMV amp, that gets masked by the power tube control grid clipping.
A regular type 4 may be best suited to them.

[Steve A.]

My 2 cents: I put a crossline post-phase inverter master volume in a Princeton Reverb and hated it. Yes, it lets you turn up the preamp volume with less power tube distortion. However, distortion in that portion of the preamp is not sweet to my ears and there was a distinct muddiness by the time the PPIMV was turned down enough to make a difference.

You might try a crossline PPIMV as a quickie experiment; however, it's the worst variant of master volume in my experience (which is limited).

Agreed! The cross-line MV cancels out the undistorted signal as you turn it down leaving you with the fizzies at low settings. A pre-PI MV works much better IMO although the one that replaces the two 220k bias resistors with a 100k or 250k linear pot works the best.

I would alternately recommend looking into a fairly transparent low gain OD pedal like a Timmy or a Barber LTD. They give me the sound of a cranked BF/SF amp at lower volumes but YMMV...

Steve Ahola