Big Genes Official FAQ

Hardware Big Genes
1

Is it safe to connect USB while Big Genes is powered by Eurorack power?

Yes, in fact this is the intended use case. There is proper protection and a power switch handles USB power so there are no power conflicts.

Being able to power (the digital part of) Big Genes via USB is only for convenience, for example you can upload a patch, access the SD card etc. without having to start up your whole Eurorack case.

2

My audio I/O, CV I/O and the upper pots do not work! I am powering Big Genes via USB by the way.

The audio and CV I/O parts (which includes Pots 1-4 as these are summed with CV) require Eurorack power (+12V/-12V) to function properly.

3

When I turn any of the upper 4 pots, their values affect each other, and (possibly) also the CV I/O values drift up or down depending on the pot positions.

Users have reported that in some cases (no pun intended) the -10V analog voltage reference (Test point AREF_-10) is not strong enough and will drift depending on the load.

If you suspect that your values are drifting, check the voltage on the test point “AREF_-10V”. It is on the Big Genes PCB but slightly hidden under the Ksoloti Core. If you measure anything other than 10.0x V (though 9.95V to 10.05V is perfectly fine) OR if you measure different voltages depending on where the upper 4 pots point, you may want to try one of the two fixes below.

There are two possible fixes to stabilize the voltage reference:

  • Solder a 1k resistor parallel across R72 to supply (about 2mA) more current to the LM4040 -10V reference.

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    R72 is 560 ohms but it seems we may have to go even lower. 560 and 1k in parallel would result in about 358 ohms, supplying up to 5.58mA to the LM4040. Well within specs still.
    Disadvantage: the LM4040 might warm up more, which would slightly affect AREF-10 during warmup. You might get that vintage “it needs to warm up for 10-20 minutes” feel, numbers drifting towards stability, which may or may not not bother you on a digital module.

  • Replace the upper 4 pots with higher resistance ones.

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    This will reduce the AREF-10 current flowing through them, increasing voltage stability. B25k or B50k is fine, maybe even B100k.
    Disadvantage: Higher resistance pots might be noisier and exhibit more jitter.

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4

I just added the PDM breakout thing to my Big Genes and it doesn't work at all! My Big Genes PCB is v0.6 by the way.

There is a mistake on the v0.6 main PCB boards Two pins were swapped by mistake. Sorry about that! This has been fixed on v0.7 and later PCBs.

For v0.6, a working fix is here:
https://modwiggler.com/forum/viewtopic.php?p=4223038#p4223038