2-second switcher question

[kissack101]

Above is a basic schematic for my switcher pedal.

The idea: The toggle switch on the top left of the picture determines whether or not the 'decay' from the delay pedals can still be heard after you remove them from the loop, in the 'up' position you can't, it cuts everything out, in the 'down' position you can.

The reality: In the 'up' position, everything works fine. In the 'down' position, you can still hear the decay from the delay pedals, no signal is going to the pedals in the effects loop, but you can no longer hear the guitar.

The question: Why not? And what can i do so that in the 'down' poistion, you hear the last decays of the delay pedal but still hear the basic signal coming throught he switcher?

Any help would be much appreciated.

Adam.

[SaBer]

I couldn't quite figure out your picture, but I think you are trying to mix two signals without resistors or a mixer. So actually you are connecting the output of your effect to the output of your guitar. Thus you are also connecting you guitar to the volume control of the effect, on the "wrong" side! So the high impedance of your pickups, is connected to the low impedance of the volume control, attentuating almost all of the signal.

So what you'll probably want to do is:
1) true bypass only when you don't want the decay
2) a buffer for your guitar, and an active mixer when you do want to hear the decay

[kissack101]

Hey,

thanks for the help, seems like my (almost non-existent) knowledge of electronics has let me down again. But I suppose learning about this stuff is why I come here and what better way to do that than to try and fail?

Your solution sounds like exactly what i'm after. So on the yellow wire on the diagram, it needs to go: 'Effects In' Switch --> Buffer --> Mixer --> guitar output ?
Or does the Buffer go before the blue 'guitar in'? and the mixer after the 'Effects In' switch?

In terms of the mixer, could I just use this: http://www.aaroncake.net/circuits/mixer1.htm but with the two pots (R1 and R3) removed and connect the capaciters straight to the resistors?
Also, there seems to be dozens of different designs for buffers, do I need an input buffer or an output one? And which is a good one to use? (size may be an issue, i'm only using a small MXR-size box...

Thanks again

Adam.

[SaBer]

If the delay is your last pedal, it's pobably not worth making it true-bypass. If you want true-bypass it gets pretty complicated 

So what I would suggest is:
1. op-amp buffer: non-inverting, with gain of 1. http://www.generalguitargadgets.com/pdf/ggg_ic_buffer.pdf without the switching
2. op-amp mixer first stage of this: http://www.generalguitargadgets.com/diagrams/mixer_sc.gif
So you only have a dual op-amp, three resistors and the biasing-stuff. 

So, you have guitar input going straight to buffer, then a footswitch selecting either to go to the effect or to mixer channel one. Mixer channel two has the other half of the footswitch selecting either direct output from effect, or via a switch, that cuts the signal when necessary. Do you understand?
Then, if you want a LED, thats easy to add with a 3PDT footswitch.