This topic is dedicated to discussions about the overall MICRORACK system. Here you can find our technical specification, share insights on the hardware components such as breadboards, rack mounts, adapters, wiring solutions, and other related hardware.
Link: MICRORACK System and Modules Technical Specification
There is information about mechanical dimensions, power, signal levels.
TL;DR
separate breadboards not mixing audio;
has anyone else had the issue where you have two patches going on separately powered breadboards, but want to mix them together on one of the two breadboards but you just get buzzing when connecting?
I did not experience this, but I would expect it, if the grounds of the two boards are not connected to each other.
One wire connecting GND of one board with GND of the other should resolve the issue.
duh!
yes that fixed it right away. thanks!
Just position the boards horizontally and power them with a single module in between, saves a power module and gives you some free space for other modules, plus the cables stay mostly out of the way above the knobs and buttons.
Thanks for the help, everyone! Yes — if two setups are powered separately, their GNDs need to be connected first. It’s important to do this before linking the modules together, otherwise there’s a risk of damaging them. We’ll add this to the documentation.
If there is a risk of damaging modules without this GND link, maybe it would make sense to use two GND links, just in case, for reliability?
And thus the famous ground loop was born. 
Seriously: (almost) no danger of ground loops here, and it makes sense to make the ground connection extra secure.
This is an area where the bigger modular systems are better: with e.g. Eurorack each signal cable brings its own ground along, so you can never forget to connect ground.
power module has 4 gnd pins so you can use all of them xD
In practice, when connecting a patch cable between two separately powered eurorack setups, there is a risk of injecting a dangerous electrical potential difference into the signal path, since the sleeve (ground) is not necessarily connected first.
Also in Buchla world you have to connect ground terminal first because of banana plug
So far nothing seems damaged,
Out of curiosity;
For how long, how strong, or what type of signal do you suspect would do damage if not grounded between separately powered breadboards?
It totally depends on the power source you’re using. The potential difference between two different power supplies can reach 50–70 V. This is not dangerous for a human because the current is very small, but it can be dangerous for modules. That’s why a good rule is to always connect ground first.
Thanks!