Simple two channel DRY/WET passive mixer?

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Simple two channel DRY/WET passive mixer?

Postby Virtual Aaron » Tue Oct 03, 2006 5:11 pm

WANTED: A box to split and blend a mono signal for parellel compression and other such black arts.

A single spaced rack unit with two IN's and one OUT and a big silver knob to blend em would be ideal.

I can split the initial signal from my patch bay, but, would this need to be buffered on both the splitter AND blender ends?
Any techs wanna help me out on this one?

This has got to be a usefull device for mixing without a desk.
Why don't more compressors have a dry/wet control anyway?

Cheers,

Aaron
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Postby chris p » Tue Oct 03, 2006 10:36 pm

Balanced or unbalanced, Aaron?

Concept is simple: Its a double ganged pot (say 10K linear) for the mixing:

Gang 1 positive being InA +
Gang 1 wiper going to the output via a 2k in series
Gang 1 neg going to InA-

Gang 2 positive is InB -
Gang 2 wiper also going to the output via a 2k in series
Gang 2 neg is InB+

As you turn the pot, you get a passive mix starting at InA, ending with In B, and going through a 50/50 mix in between.

However, this makes lots of assumptions about common ground levels, impedances and output voltages. You might try it and see if it works for you, but a more thorough design would look at individual pots for InA and InB levels with an IC or tranny buffer to deal with any nasty impedance issues. This is much more in the territory of Rob or Howard.

Good luck
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Postby Virtual Aaron » Wed Oct 04, 2006 1:52 pm

Thanks Chris,

That is the dead simple approach I was after, the things I would normaly 'blend' is A: guitar stomp box boosted through a pre amp and B: distressor. Both these have balenced outs but with short leads etc unbalenced 'should' not be an issue. It would however need to be dead quiet. The pre amp I use has a transformer on the output, as for the distressor?? not sure. That would have to help, right?

I'm pretty green with electronics theory, I've built plenty of stuff (the pre is a JLM) but don't ask me to design anything but an A/B switch!

Cheers
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Postby rob » Thu Oct 05, 2006 10:57 am

almost Chris

i think this does it. It will require a both the A and B units to have a reasonably low output impedance to achieve low bleed of the B signal when fully cranked in the A direction ( and visa versa ). In practice it should be fine
Image

the ground connections are optional and it works best with balanced sources and sending off to a balanced input

Rob
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Postby Virtual Aaron » Thu Oct 05, 2006 2:00 pm

Thanks Rob,

This will be my cheapest build ever!
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Postby rob » Thu Oct 05, 2006 2:32 pm

yeah...just don't cut any corners on the case....remember its all about how it looks!

R :)
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Postby Virtual Aaron » Thu Oct 05, 2006 8:13 pm

Absolutely, so how would I put a VU meter in it???
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Postby Virtual Aaron » Thu Oct 05, 2006 8:14 pm

Joking, of course

Ta,

~A
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