Creating a simple blended compressor

[lemondrop]

Although this is more about a pedal than a guitar, I thought it might be relevant here.

I haven't used a compressor in years, but I'm interested in the newer pedals like the Wampler and Barber Tone Press which combine the dry signal with the compressed signal.

But instead of buying one with the blend control, could I get a near 50/50 blend by splitting the signal, running one wire-pair around the pedal (MXR Dyna Comp) and re-summing them after?

I would use 10k resistors on each line as mentioned here:
www.tkk.fi/Misc/Electronics/circuits/linesum.html

I've made a very rough diagram here, the signal goes from right to left (pardon my limited art skils)



Might that work? Or would I need different resistor values? Thanks in advance.

[ashcatlt]

That'll work reasonably well for a low-Z active input. Unfortunately, I don't think it will make your hi-Z passive pickups very happy. If this is going to be first pedal in the chain (usually the best place for a compressor) it probably won't produce acceptable results.

You could put a buffer in front, and probably get it to work. The easy way to accomplish this would be to use about any big name pedal (non-true-bypass, buffered like Boss or something) in bypass mode before the split. You could also google something like "effect loop pedal schematic" to find a DIY solution.

[JohnH]

yup to what Ash says. A Boss tuner pedal would be a good and useful thing to provide buffering to the dry signal

J

[lemondrop]

Thanks guys - here's a variation of the question... consider the Voodoo Sparkledrive which is somewhat similar except that it blends the dry signal with an overdrive.

Forget the previous compressor for a second - it's not in this question.

If I were to do that same trick above... split the signal and run it around an overdrive and sum it after with 10k resistors, might that work?

And it would NOT be the first pedal in the chain. Might this trick work Ok to create a simple "Sparkledrive"?

[ashcatlt]

Doesn't matter what the pedal is, really. You're almost assured to need something acting as a buffer at some point before the split. It's not going to hurt anything if you want to try without, though.

I have some concerns re: the mixability of the signals as well. As is, all you'll have to adjust the balance between the effected and dry sounds will be whatever output level control is on the pedal. This could work fine, but things like overdrives and compressors generally have the capacity for a lot of gain.

[ChrisK]

And, what is the phasing and/or delay thru the compressor. If the pedal has a gain of -1 (the output is inverted with respect to the input), you'll be subtracting.

[lemondrop]

ChrisK, good point - I forgot all about that - the phase reversal combined with the dry signal will cause cancellations. End of experiment. That's why the Barber mentions the "parallel compression" thing.


But I'm still interested in doing this with an OD though. Do OD's have phase reversal? Years ago I sorta tried it with a Scholtz Rockman, but without the resistors. It sorta worked.

Are 10k about the right value for the resistors for this with an OD?

[ashcatlt]

Some ODs will flip the polarity as well. Depends on the circuit. Only a couple ways to find out.