FX send: mixer-like effect pot to channels schematic

[fatecasino]

I am building a small 2 channel amp and I just built a small time echo/delay for it. Instead of inserting this into the end of the preamp line, I was wondering how could I insert it in way like the effect pots in a console/mixer where you can add as much effect as you want to each channel seperately?

[ElectricDruid]

If you're building a two-channel amp, you're talking about having two "FX send" knobs to control how much signal goes to the delay, right?

In which case, you'd have a op-amp mixer circuit in front of the delay circuit (replacing the buffer, which wouldn't be needed) and the input knobs of the mixer become your "FX send" controls. Then you've got to mix the wet/delayed signal back in with your straight-through signal. The Small Time has a mixer on the output for that already, so no problem.

HTH,
Tom

[fatecasino]

If you're building a two-channel amp, you're talking about having two "FX send" knobs to control how much signal goes to the delay, right?

yes, exactly!

(replacing the buffer, which wouldn't be needed)

could you explain this a little bit further please?

In which case, you'd have a op-amp mixer circuit in front of the delay circuit (replacing the buffer, which wouldn't be needed) and the input knobs of the mixer become your "FX send" controls. Then you've got to mix the wet/delayed signal back in with your straight-through signal. The Small Time has a mixer on the output for that already, so no problem.

well, there's something I don't understand. You mean that the signal from each channel goes to the op-amp mixer volume control and then through small time. But then by changing the "FX send" vol  the actual clean signal volume will change too(or not?). I want to change the FX volume of each channel only.  The small time mixer increases/decreases the volume of the delay volume only  leaving the clean signal untouched.

After some reading, I am thinking of this design, but I am not really sure 

input->vol knob->tone knob ->clean signal -> Y spliter ->vol knob (send vol in fact)->delay FX->mix with clean signal (from Y splitter).
In addition, I have to kill completely the clean signal from the delay circuit.
Do you think that this is going to work?

[ElectricDruid]

First, the delay is this, right? Just checking we're on the same page:

http://www.valvewizard.co.uk/smalltime.html

Your idea of the overall scheme is fine. You split each channel's signal ahead of the delay. The clean version goes straight to the final output mixer of the SmallTime (The TL072 on the RHS).

The other signal goes to a similar mixer that replaces the buffer stage at the front of the delay. The buffer needs to be converted into a mixer because instead of only dealing with one signal, now it needs to mix the signals from both channels.

Essentially, you're using the output mixer of the Small Time circuit to mix the wet signal back into your clean signal before it heads off to the power amp or whatever else you've got next.

HTH,
Tom