More of a builder than a designer is thinking about stereo harmonic tremolo

[roarshock]

Hi there,

I love trem, vibrato, and harmonic trem. If it wiggles, I like it.
I was struck by Passolutre's post https://el34world.com/Forum/index.php?topic=32551.msg361093#msg361093 , and wanted to build something similar. Recenty this chassis came my way: an RCA RS-177A that is a push pull stereo with plenty of heater current (5.7amps of 6.3v) for my loose plan.

In Passaloutre's circuit, the power tubes are fixed bias and the trem signal wiggles the bias voltage of the power tubes. My current schematic runs cathode baised EL84s and wiggles the grid leak resistors, similarly to the Gibson GA-19RVT. Does that look correct?
I am interested in wiggling the last triode before the phase inverters instead, to increase power tube life. Is there merit in that idea? This is surely in the idea phase so the preamp may change or get other complications tossed in. I am considering how to build the cabs too, as I would like to separate the speakers to get the full impact of the wobble, but be able to move them as one if possible.
Your thoughts, insights, experience or even guesses would be valued. I love learning from the conversations here.
I've attached passaloutre's schematic and mine for your consideration.

[passaloutre]

I would keep the wiggle on the power tube bias, to gain the common mode rejection, and I don’t think it will shorten power tube life. You can still keep it cathode biased and wiggle the grid leak reference.

That preamp has a lot of gain, considering the relatively low loss of the Tweed-era volume/tone controls. You may need it to recover from the reverb, but you may find it a little hot, depending on your tastes. Especially considering the extra sensitivity of the 6BQ5s. I modeled mine after the 6G3 Deluxe, which is already pretty hot, even with the split load on the second triode to reduce its gain. Then again you might like the extra grind for your best Lonnie Mack tones. Also if you're interested in AC30 and Marshall 1974 tones, there's no reason you can't use LTP phase inverters. I really only used the cathodynes because I was already using one to split the tremolo, and I liked seeing three of them on a schematic.

As far as cabinets, just for a point of reference, mine sits in the original Magnavox console, which houses a 15", a 12", and two small tweeters (disconnected for guitar use). In "compact" single cabinet mode, the low-frequency side is connected to the 15", and the high-frequency side is connected to the 12". The back of the amp has a speaker-out patch panel with two parallel outputs for each power amp, so that when I use it in "spread" stereo mode, with two cabinets, I can patch the internal 15" and 12" to the low-frequency side, and send the high-frequency side to a 2x12" across the room. Or alternatively I can connect the high-frequency side to the internal 15" and 12" and send the lows to my bass guitar cabinet across the room. All of these offer unique stereo spreads and valuable variations on the theme.

If you have an extra tube socket and cabinet space, I also think it would be really cool to send each side to its own reverb tank, after the crossover. Then you could have different characteristic reverb tanks on each side, to really enhance your stereo separation.

This is one of my favorite creations, and I can't overstate how cool it is to sit in between the two cabinets seesawing back and forth. I have another stereo single-ended chassis that I would like to make into a smaller version of this someday, and I really look forward to seeing how this works out for you.