Series/Parallel Delay Volume Issues

[jghfslk]

I'm attempting a multi-delay build and am trying to work out the switching to go between having the delays in series or parallel.  I've done this a few times, but my method has always had issues with volume differences.  I've typically used this configuration:

Input into a splitter:  http://tagboardeffects.blogspot.com/2014/08/amz-2-channel-splitter.html

I wired the series/parallel switch using this layout:  http://www.rhythmanddetonation.com/wp-content/uploads/2011/01/SERIES-PARALLEL.jpg

I then used this layout to mix the signals:  http://www.sabrotone.com/?attachment_id=3039     I did omit the blend pot and just wired both signals after the 10uf capacitor to the output.

When in series mode, I get a drop in volume.  I tried getting rid of the mixer all together and just wiring both outputs of the delays directly to the effect output.  When doing this, I get unity gain in series mode, but a volume drop in parallel mode.

Can anyone think of a better way to accomplish what I am going for? Or explain why the volume differences occur using the different methods?  I can draw up a diagram of exactly how I wired everything if that will help.

Thank you!

[bsoncini]

Maybe it's a phase issue. You could test something like this to see if it helps.

https://www.parasitstudio.se/stripboard-layouts/archives/10-2017

[jghfslk]

I don't think it is a phase issue.  The blend circuit has the option to reverse the polarity and when I tried that the signal cut out completely.

[reddesert]

Generally, it doesn't work well to put two outputs directly in parallel.  Outputs are typically low impedance but not equal between different circuits. What happens is that you have two voltage sources trying to pull each other around, and the higher impedance source winds up loading the lower impedance source. Imagine that you had a 9V battery and a halfway-dead 9V battery that was only putting out 7V in parallel.  The total output would be about 7V and the good battery would be dumping current into trying to charge the bad battery. The same problem happens with AC signal outputs.

The way that people usually deal with this is to put mixing resistors between the individual outputs and the final output. In your case that could be restoring the blend pot in the  Runoffgroove schematic mixer: http://runoffgroove.com/splitter-blend.html. Or just use two 10K or 22K resistors from the A and B output to the final output.

I'm also not sure that the series / parallel switch and that Sabrotone layout are doing what you want.

The Sabrotone layout doesn't seem to be the full ROG schematic as Sabrotone only has one send/return. So I'm guessing that you have to wire one effect output into the mixer input and the other into the mixer return?

Also, the series/parallel switch shown (with the 4PDT) hardwires the two effect outputs together in parallel. Did you change it somehow to run two outputs into the A and B sides of the mixer?

[jghfslk]

Thank you for the info! 

If I use the same delay circuits and wire the two outputs from the mixer, will there still be impedance issues?  From what I can remember when I was first experimenting with running delays in parallel was that I got a louder signal when wiring the mixer outputs directly to the output rather than using the blend pot.

I did wire the switch so when in series mode the signal goes through both effects but uses only one half of the mixer.  My guess is this is why there is a volume drop when the effects are in series rather than parallel.

I'm going to try a different method using a different mixer circuit to try accomplish what I'm going for. 

[diablochris6]

I made a bizarre series/parallel mixing circuit for three effects that essentially uses info from the "Panning For Fun" article found on Geofex. My circuit allows for series and parallel circuits while also allowing a blend between the two. You can find the schematic for the Phantom Pain audio splitter circuit in the Google Drive linked in my signature. I also have some PCBs of this if you are interested.

[jghfslk]

Thanks for the suggestion and offer Chris.  I actually bought a couple of phantom pain boards from you a while back.  I used one and built it as a modular unit.  I'm still deciding what to do with the other one..