using 1/2 an AX7 as effects return?

[iknowjohnny]

I was thinking about that extra 1/2 of an AX7 i have doing nothing since i dumped the cathode follower stage and it hit me that this may be the perfect thing to use it for. But i have questions. I have a pre PI master right after the tone stack like a 2204. tell me where i am wrong if you see reasons this won't work.

What i was contemplating is taking the signal from the output of tone stack and going to a pot that would adjust the level if it's too hot for the pedal. I don't think any pedal would need more signal, so all i'd need was attenuation there. The return would go into the unused tube stage and to a second return pot and from there to a master. Everything would be bypassed when the loop isn't being use, and if i can't do that with switching jacks i could use a switch, doesn't matter to me. besides, switches are far more reliable than those darn switching jacks.

assuming you tell me this will work, I do have one issue i don't know how to resolve.....how would i match the pedal to the tube stage? Will it be ok as is? I suspect it should since it would be the same as an input 12ax7 stage taking the signal from a pedal. so would i just wire it up like a input stage and if so how would i determine the cathode values to color things as little as possible?

Any advice would be great because as you can see i'm flying blind here as usual.

[Jana]

Too many pots to fiddle with.

1. Plug into your amp, connect an AC voltmeter to the wiper of your current master volume. Crank up your gain to a distortion level and adjust your master volume to give you about 100mv. output on the wiper. Turn everything off and don't touch the master. Disconnect the wires from the master and measure the resistances on from wiper to both sides. Those are your approximate values for the voltage divider that will now go to the effects send.

2. Wire up triode with 100K plate, about a 1K to 2.2k cathode, no cathode cap. 220K grid leak resistor, connect effects return to the grid.

3. Use a .022 uf cap from the plate going to a 1meg pot, your new master and then to the PI.

Test and tweak resistance values if needed. It should be really close though.

[iknowjohnny]

Thanks Jana ! great post. Should be a sticky ! I'm cut and pasting this and saving it and will give it a go soon.