Parallel Box

All frequent questions on switching: true or not true bypass, transistor-based or mechanical.
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snk
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Post by snk »

Hi
I would like to build a simple passive box which would allow me to run two signal paths in parallel :
- One dry (with a volume control),
- and one going to an external effect loop (with pre and post volume control).

Image

I have been using a passive mixer schematic i had found a couple years ago on the web (i think it was from Beavis audio website, but i can't find it anymore), and tried to modify it to suit my needs.
Overall, it's a very easy project, but I am rather new to DIY, so i am not sure my schematic is good.
Could anyone give it a look and tell me if it is allright ?

Mainly, I am not sure if the black wires (negative/ground) are all connected as it should.
Thank you in advance for any advice.

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snk
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Post by snk »

[edit : I have found back the circuit i haved use as a starting point is this one, from Experimentalist Anonymous]
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Hideki
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Post by Hideki »

In all the drawings, ground relies on getting its connection through the chassis. I wouldn't count on always getting a reliable connection that way, so I would simply run wires connecting all ground points together inside the box.

The effects send jack doesn't mix any signals, so you don't need the extra resistor there.

Resistance values are very high, which makes sense if you are running directly from a guitar. If the inputs are buffered at least once, I would make the pots and series resistors 5-10 times smaller.

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snk
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Post by snk »

Hello
Thank you for your answer, and sorry for the late reply, for some reason i didn't get the reply notification.
In all the drawings, ground relies on getting its connection through the chassis. I wouldn't count on always getting a reliable connection that way, so I would simply run wires connecting all ground points together inside the box.
In the meantime, i have updated the design with grounds wires in a "spider web" configuration.
(there is an error with the potentiometer's label, which are swapped).
Image
The effects send jack doesn't mix any signals, so you don't need the extra resistor there.
Ok, but does it make any harm to the circuit if i keep it ? (not that i want to keep it, but i'm trying to understand better the consequences).
Resistance values are very high, which makes sense if you are running directly from a guitar. If the inputs are buffered at least once, I would make the pots and series resistors 5-10 times smaller.
Ok, interesting point.
I borrrowed the resistor values from the Beavies Audio schematic.
500k for the potentiometers is used to avoid treble loss.
I am planning to use it mainly with synths and drum machines (so everything should be line level), but maybe also with a passive electric piano so, a bit like a guitar).
Therefore, my questions would be :
- Is there any "once size fits all" resistor value (suitable for both synths and passive instruments) ?
- Is there any issue or risk by keeping these values (like more noise, hum isues, etc) ?

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