mod to make AA864 channels in Phase - clean

[half_smith]

Hey all,
I want the 2 channels to be in phase (like in the 5F6A) because I like to jumper the Bass Ch to be a pseudo effects loop for reverb - gives me the un-reverb signal straight into Normal Ch. and I can blend in Bass Ch (100% wet reverb).
Obviously I'm getting phase cancellation and I want to remedy that.

I want to mod the second triode of V1 to be a cathode follower, placing it before the tonestack.
I guess I could omit that triode completely, but it seems like a clever idea to make it a cathode follower (not phase inverting) and help drive the tonestack (impedance) as well.

*I never want to overdrive the Bass Ch. it's only for a clean reverb signal.
*I don't want to trainwreck the Normal Ch, I like clean headroom

Help with wiring ?
Can I just connect pin3 to pin7 (V1)
put a 100k resistor between pins 6-7
wire pin 6 to ground
wire pin8 to the tonestack (where pin3 used to go)
wire from Volume to pin7 (V2)

Will anyone look at this mock-up I did and advise?

Advice?
Thanks!

[sluckey]

I want to mod the second triode of V1 to be a cathode follower, placing it before the tonestack.

The idea is feasible but your description of the wiring changes is flawed and both your modified drawings have errors. I'll fix the schematic drawing and you can correct the layout to match the corrected schematic.

[half_smith]

thanks Sluckey, is your only change the connection from V1 pin8 out into the tone stack - you cut the 100k to ground?
I went over that a few times before I drew it, I figured I would need the 100k voltage divider there but yeah, I knew something was wrong.

[sluckey]

thanks Sluckey, is your only change the connection from V1 pin8 out into the tone stack - you cut the 100k to ground?

I cut the 100K that was connected to B+.

I also removed the 100K that was connected between the volume pot wiper and B+. I also removed the .1 and .001 caps and two 220K resistors, so the volume wiper connects directly to V2 pin 7.

[half_smith]

gotcha, I was looking quickly while I was at work and was only focused on the first tube.
I needed some help to think it through, thanks!

Any thoughts on how this will sound or change the tone?
vs what if I just omit the whole triode?

[half_smith]

how's the layout now?

[martin manning]

I want to mod the second triode of V1 to be a cathode follower, placing it before the tonestack.

Are you mod'ing an old Fender or a clone?

[sluckey]

Your new layout will work. I have no idea how it will sound. Try it and you can tell us. May I suggest mounting the 100K between pins 6 and 1? That's more customary and IMO looks neater than mounting between pins 6 and 7. Most people just poke the resistor lead through pin 1 and bend it around to connect to pin 7. Either way is electrically the same. Looks kinda like this...

[half_smith]

perfect, thanks Sluckey!

Martin, this is a '68 dripedge, I've been messing around with it for years, tried lots of mods, returned it to BF, etc. It had already been violated when I got it for 200 bucks from a garage sale.

[martin manning]

Have you looked at the 6G6-B schematic? Delete the last stage on the bass channel and move the Treble pot back to the tone stack.

[half_smith]

I made the mods, it's pretty interesting. The Bass Ch is very clean and chimey, more responsive to the tone stack.
Not very loud, not much gain, it keeps a perfect sine wave even when dimed - which is perfect for my use as a reverb only mix.

Interaction with the Normal Ch is good, no phase issues.
I'll have to see how it sounds with my cabinet (I've only heard it through my test speaker).

Martin, thanks for the suggestion. I might go back and try something like that too.

[half_smith]

*deleted

[half_smith]

The simple CF mod I did on Bass Ch is good for the phase issue but too weak of a signal, I'm gonna first try bootstrapping it maybe that will be useful here, apparently folks have had mixed results with BSCFs

[sluckey]

You can roll it any way you want but a cathode follower will always have a gain of slightly less than one. IOW, put in 1V on the grid and you will get out about 0.9V on the cathode. Don't waste your time trying to boost the voltage gain of a CF.

Experimenting with a cascode circuit may be worthwhile. See https://www.valvewizard.co.uk/cascode.html

[half_smith]

Cascode, whoa, a whole new rabbit hole. Thanks

What about something so simple as adding a Cathode Bypass cap to V2 (doesn't have one at the moment) to add gain to the Bass Ch.?