Splitting and combining a signal.

[Radamus]

Hello,

I am preparing to build a stereo echobase (http://www.diystompboxes.com/smfforum/index.php?topic=71201.0). I'm changing how I want the output to work. Basically, the circuit has two outputs, one from each chip, which are both buffered with an opamp. When you take sound off of the second ouput, a longer delay comes out. When you take both outputs, a rhythmically variable output comes out. I'd like to have both options whether I'm using one speaker or not.

The problem comes down to this: In one case, I have to combine output A and output B in one output jack. In another case, I have to take output B and split it to two speakers. I know very little about buffering and combining signals, so I'm looking for help. I have looked up a couple of other designs out there, but I've found that they either use opamps with audio into one input and the other input connected to the output (unity gain) or they use a resistor. I have one extra opamp as it is because I cut the clean signal ouput, and I can work in more if it's the only way to have all of these options.

In case I didn't make it clear, when one output is used (the other is a switching jack), a footswitch controls whether the ouput is rhythmic delays or extra long delays. When both outputs are used, the footswitch determines if the output is ping pong or long delay to both speakers. The ping pong delay in two speakers and the long delay in one are already in the schematic pretty well at this point, and I would be modifying the mixdown part.

So, can I do the mixing and combinations here with resistors alone without causing too many problems, or do I need to go the buffered route? I have one extra op amp already, is that enough?

Thanks

[John Lyons]

The splitting is simple with a buffer and taping the split after the buffer.
You can combine with resistors but you will need to experiment with values.

John.

[Radamus]

The splitting is simple with a buffer and taping the split after the buffer.
You can combine with resistors but you will need to experiment with values.

John.

That's a simple enough answer. Just so I make sure I understand, the first part there is that I run both signals into one part of a single opamp, and then take the output of the opamp as the output for two?

And as for the combination, I'm curious as to what happens if I don't use them at all? Does one negate the other?

***
In the middle of my post, I looked at my switching again and I realized that it made no sense. Really, I'm not sure what I was thinking. I've revised it so that I use the standard mixdown section, only reversing A and B, so that B, the longer delay, is dominant. Then, A mixes into B when a footswitch is in one position, but only if no jack is in the switching jack. In that same footswitch position, output A connects to circuit output A. In the other position, mixdown does not occur ever, and output A connects to circuit output B. So now all I need is the splitting part, though according to what you said, splitting after a buffer is just fine, which the circuit already has. I don't suppose it would be too much trouble to ask you to double check that by the schematic?

Or should I duplicate the output buffer of A (B for my purposes) with the extra opamp? One way it connects to nothing, the other way it connects to the B (A for me) jack?