How to parallelize and blend 2 dirt circuits

[add4]

Hello there.

I would like to put one OD and one fuzz in parallel, and then be able to blend them.
I guess it's far from being as simple as just splitting the input, and connecting both outputs to the output jack. so i'm asking for your knowledge

Issues i imagine:
- impedance of the 2 circuits should match, or a circuit block should be used to make sure that both circuits receive the signal 'equally'. (buffer?)
- phase : if both circuits are out of phase, you can't just mix them without adding a circuit to correct the phase issue.
- mixing both signals should also be done wit ha specific circuit.

Would that be a job for the ruboffgroove splitter-blend http://www.runoffgroove.com/splitter-blend.html?
or is it potentially more complicated?

is it possible to just use two 12k resistors instead of the 25 k pot at the end of the circuit and expect that the output volume of the dirt circuits will play the role of the mix knob?


Thanks in advance for your help

[samhay]

Do you have a specific OD and fuzz in mind?

[add4]

TS type and fuzz face
does it matter? as long as the volume difference between the outputs is not HUGE, i would think it doesn't matter? or am i missing something?

[samhay]

Neither of those are inverting, so you don't need to worry about phase.
They have very didn't output impedances, which may make passive mixing tricky, but for a first try I would try this - 2 resistors or a (temporary) pot on the output.

[add4]

Ok, so passive mixing is an option? nice to know.
i'll try that and report back the result
migh take some time as my building time is between 11pm and 1am these days

[MrBinns]

you might be interested in a panner circuit

http://www.geofex.com/Article_Folders/panner.pdf

[midwayfair]

Always make sure the signals are in-phase at the mix point.

I would use a dual gang volume control with a buffered output after each volume control and mix the signals at the buffer outputs.

Don't use anything that looks like one pot panning between two outputs. It will sound like crap. Seriously, you'll see it everywhere. And then you'll see a million posts "I don't like how this works/I can still hear A bleeding into B/it gets quiet in the middle how can I fix that." Just don't use it in the first place.

RG's panner works for avoiding the dual gang but doesn't save much in the way of circuitry otherwise. Regardless of what you do, the ideal situation involves complete separation of the two signals and a way to completely zero out the volume of each side, and there's really no getting around a dual gang for that. You're mixing two DIFFERENT signals to the same destination, rather than the same signal to two different destinations like what would be done in e.g. your stereo, so the dual gang is the way to go.

EDIT: block diagram.

Input buffer > Circuit 1 > pan control gang 1 > output buffer > mix point > master volume control
                 > circuit 2 > pan control gang 2 > output buffer |

You can use resistors to separate the pan controls from each other and then use a single output buffer, but I don't think it will work quite as well and will lose you some available output if that's a concern.

Or make each pan control a separate volume control, you can do that, too.

And no, you can't get around the input buffer. Your fuzz face would load down your TS and make it sound like crap. If you hate the sound of a buffered fuzz face, you'll have to live with not putting them in parallel.

[JohnForeman]

Build this
http://www.guitarpcb.com/apps/webstore/products/show/3456364

[blackieNYC]

 Looked into this too. The fuzz face just doesn't sound as good with a buffer, and there's no getting around the buffer.  But I love blending dirt.  Instead of the fuzz face, mix in a MXR dist+, or use the mix to tame something wacky like the uglyface or one of Parasite studios' recent offerings.
I strongly suggest a simple filter option - a low pass filter switch on one split (before the fuzz. Or after!) and a hp filter on the other.  Treat the lows one way and the highs another way.  The tone split of the big muff filter is a good crossover point to start with.  Simple, with a toggle switch inserting a filter into each branch of the split. Polarity reversal option is a must.  (Whichever polarity is louder.)

[PBE6]

I'm not so sure that you can't get away without eliminating one of the buffers. What about this?

The buffer side chain should present a very high impedance to the guitar signal, making it effectively invisible to the Fuzz Face and preventing buffer/loading issues. The return portion is cribbed directly from the ROG Splitter/Blender, which works wonderfully.

EDIT: oops, there should be a capacitor on the output of SEND 2

[ashcat_lt]

The buffer side chain should present a very high impedance to the guitar signal, making it effectively invisible to the Fuzz Face and preventing buffer/loading issues.

The Fuzz Face itself "loads down" the guitar pickups, completely killing any treble that might come from them.  This absolutely will effect the sound of the TS side, and most likely not end up being what you want.  The TS itself pretty much is a high-Z buffer.  What you need is a buffer into an LPF (I'd just use a cap-to-ground, but if you want to be "authentic", look up the AMZ pickup sim) on the Fuzz-Face side.

[PBE6]

Ahh yes, got the loading part turned around.

[midwayfair]

I think your tube screamer is scaring your fuzz face hehe.

the TS looks a little distressed as well, though. Maybe it's scared of beards.

[PBE6]

Lol..on second glance, my Fuzz Face looks like Bane! Definitely a cause for consternation.

[J0K3RX]

Maybe you could use 2 amps and run stereo...  Then you could really mix, control and have a ton of tonal options at your fingertips... Besides that, mono is a disease.

[karbomusic]

I would use a dual gang volume control with a buffered output after each volume control and mix the signals at the buffer outputs.

I agree with ^this idea.

Don't use anything that looks like one pot panning between two outputs. It will sound like crap.

But this sounds a little strong to me. I have TS output that blends with a boosted/buffered clean output (the worst combination for the issue you are describing) through a 10k pot. It's true that I can find some of the distorted signal when panned to totally clean but I must crank the distortion and its treble to the max and have to actively seek it out to hear it. IOW, in real world use, in this particular circuit it has been a non-issue. While I agree with what you want to get across, to be fair, I'm hesitant to use crap in the description.

The Fuzz Face itself "loads down" the guitar pickups, completely killing any treble that might come from them.  This absolutely will effect the sound of the TS side, and most likely not end up being what you want.

Done that, you're right, doesn't work as expected. Can't really have both, it's one or the other or attempting to emulate the loading. I decided to abandon blending a fuzz with a buffered distortion altogether.