Question: I’ve googled around a lot for this and have seen conflicting answers, so, once and for all…
What risk, if any, is there in overloading an input that receives more voltage than it expects? If I, for example, patched a +/-8v module into a moog Mother 32, which only expects +/-5v. Is it only a matter of controlling and attenuating voltages to get exactly the effect you want? Or does it present some amount of damage risk to the equipment? Very new at all this, thanks. Just now coming to eurorack after a while of messing around with desktop synthesizers (m32 & 0coast).
It’s my understanding that it all depends on the specific design of the inputs on the module receiving the input. This might be part of why you haven’t gotten a straight answer before: because there isn’t a one-size-fits-all answer to this question.
In a few dramatic cases, eurorack-level voltages (-12V to +12V) have been reported to damage commercial eurorack modules. But generally, eurorack designers engineer module inputs to be tolerant of the full range of eurorack levels and / or they design the module outputs not to be too hazardous – I believe this because there’s outrage whenever a module has a design flaw that causes faults.
There’s two sides to it: the inputs and the outputs. Inputs, roughly speaking, are resistors plus transistor gates (of a wide range of varieties and often as part of integrated circuits). Resistors won’t break until they catch fire (it can be fun!), but transistor gates have the potential to break with more slight over-voltages. We have to ask, what voltage can the input components withstand? To know that, you would have to see the manufacturer’s specifications for the parts that are used on the modules that you’re hoping not to break. On the output side, we have a voltage source with some output resistance. Ultimately, it’s power (voltage times current) that does stuff in the world, so the potential for damage depends on how much current the output can source. Often eurorack modules have output resistors built in specifically to protect other module’s inputs, and the output itself. It’s my guesstimate that output resistors plus relatively robust input components adds up to most eurorack modules playing nicely with each other – even if you use a stackcable to connect two outputs together.
If you want to make extra sure that a connection is safe, then you can add some extra output resistance by wiring a resistor in series with your output. You can do this with a passive attenuator (which is just a potentiometer) set to a middle attenuation value. I sometimes use Koma Attenuator cables for this purpose, if I’m feeling nervous about damaging something.
What you definitely shouldn’t do is plug your mains power (110-240V) into anything other than your power supply. That’s potentially deadly.
Most things should be fine as long as they have protection built in as said (and to be honest I’d consider it very remiss of a manufacturer not to do this). If you have concerns about something specific best to check with the manufacturer though just to be safe.
What will happen if you use larger voltage swings than a module is expecting is that you’ll lose some of the range of the modulator. For example, using a sine wave LFO of +/-8v on a module which expects +/-5v will mean the top and bottom 3v of the sine wave will effectively be chopped off. It might sound good, but it might not be the result you are looking for. Attenuators/attenuverters are useful modules to have around as you’ve stated.
Eurorack is a wild and anarchic thing. This is great for many things (I we wouldn’t have seen all the innovation that has happened if it had been more top-down regulated), on the other hand this also means that everybody does things as they want, and not everybody who makes modules knows what they are doing, or how to do things properly.
So, in theory, there shouldn’t be any problems, but actually, it’s complicated.
So it’s mostly as praffensperger said, it’s something that can change a lot from module to module and ultimately you’d have to ask all the manufacturers about how they did things, and then figure out if the various implementations actually play together nicely.
It could be that more current passes through it, than it was designed to handle (think a resistor burns because of heat, and also consider that whatever put out voltage that high would also be a momentary part of same circuit with too high a current). But it could also be that the voltage is high enough so that current starts flowing through part of a junction where it normally doesn’t, damaging a component irreversibly. Fiddly and potentially expensive when a single component. Worse when in an integrated circuit.
Some components really don’t like being wired in reverse. I.e. yes 12V is 240% of 5V, but even a brief -8V where it expects 0 to +5V positive only could prove quite problematic.
So yes, it depends, sometimes the risk isn’t worth it, and at other times you might discover something great by accident. But the risk is of frying the circuit.
if I recall correctly from my electronics studying years, the rules included designing to limit mistakes, and to always leave headroom / and have margin for error. I’ve come to expect these things, but am aware not all equipment fails gracefully. Luckily with sound kit and with more recent designs, overloads are audible and visible early. But modular really unties your hands to do all kinds of unexpected things. Stackable patch cables are one example.
But yea, e.g. I use MI Shades as an output stage (and mixer) when nobody’s watching.