Buffer Bypass Switch

[sturgeo]

I'm working on a new utility pedal and would like to make the primary buffer removable from the circuit when necessary. 
I'd also like an always on tuner out, I've made a quick diagram to show my intended solution.

Will bufffering the tuner out as shown negate the effect of having a parallel tuner out when the primary buffer is bypassed?



P.S. ignore the opamp pins etc, purely to show signal routing.

[GrindCustoms]

We've also worked on a buffered bypass similar to what you're attempting, we had one issue with it, bypass would work and all, but i had a constant humm when bypassing the effect, will have to check back into it.

This is what we did:

[kgull]

Will bufffering the tuner out as shown negate the effect of having a parallel tuner out when the primary buffer is bypassed?

Nope. I'd also lose SW1_A. Op amps have a REALLY high input impedance and won't have any effect on the signal. If you leave the input hanging like that you may get oscillation.

[kgull]

We've also worked on a buffered bypass similar to what you're attempting, we had one issue with it, bypass would work and all, but i had a constant humm when bypassing the effect, will have to check back into it.

Might be the circuit itself oscillating. See if the hum clears up by tying the circuit input to ground when bypassed.

[m-Kresol]

I might be utterly wrong here, but I thought that an opamp buffer always has negative input and output connected?
I also would not use the inverting (-) input of the opamp for the signal as this might have affect some effects in a bad way, iirc.

[sturgeo]

I might be utterly wrong here, but I thought that an opamp buffer always has negative input and output connected?
I also would not use the inverting (-) input of the opamp for the signal as this might have affect some effects in a bad way, iirc.

Sorry, as mentioned below the picture the pinouts are incorrect, it's only to show the basic signal flow.

Also, i forgot to label it but SW1_A pin 1 would be connected to ground.

[sturgeo]

As completely bypassing the buffer appears to cause issues with the tuner permanently connected i might change the output impedance of the buffer using a dpdt instead, selecting between the standard 560r resistor (K based buffer) and a higher value between 1-10k.

In my head this is the best way to make it play nice with fuzz and some vibe pedals, hopefully it shouldn't attenuate the volume too much 

To the breadboard batman!