Audio signal processing question(s)...

My setup includes a Rackbrute 6U with a Bastl Ciao! as my output which I run to a MOTU 828. To date I've been just running mono from it but looking now to use both L & R channels for stereo out into MOTU 828 into Ableton Live. The Ciao! says it has "balanced" 1/4 outputs...to run stereo to Ableton, would I just use a pair of unbalanced 1/4 - 1/4 (they have a red stripe on one cable and a black stripe on the other) connected into two inputs on the MOTU 828 (channels 7&8) and then each channel then has its own track in Ableton?

I also have the L(mono) and R 1/4 outputs from my Hydrasynth...seems like I would use the same type of cables from Hydrasynth to MOTU 828 (channels 5&6).

I had been using 1/4" - 3/5mm from my Hydrasynth to Ladik A-520 preamp and then into stereo mixer in on my Cosmotronic Cosmix and then main stereo out to the Ciao! but only out from L(mono) of Ciao! into one channel of my MOTU 828...so missing out on any stereo signal from Hydrasynth.

Think I want to go L/R directly out from Hydrasynth into MOTU 828...but will use a 1/4" - 3.5mm from the headphone output into the Ladik preamp to process that signal in the modular (because I can...I think).

So, for a stereo signal, I use mono cables to L/R? Is a stereo cable only used when there is a single output labeled stereo? Do each of my L/R cables need to be stereo to get 'stereo'?

use 2 mono 1/4" - 3/5mm cables L->L/R->R this will give you stereo

stereo cables are only used when a single output and input specifically state stereo

pro gear does not do this

most eurorack is pro gear

I'd also try bypassing the ciao! unless you have a compelling reason to use it - does it have a compressor in it? i can't remember

That Ciao! should be just fine, compressor or not. Since they're planning to go direct from the Ciao's outs to the A/D, it would probably be better to apply a VST to the incoming signal in the DAW itself. That way, it's possible to futz around with compressor topologies, which may be necessary for different patches. For example, with sounds that tend toward percussives, you'd want to do some basic compression to mash that a bit and keep the peaks under control, but if you're wanting to slam the hell out of a source, then using a VST clone of an 1176 with the "four-button trick" would be perfect.

As for using TRS 1/4" to 3.5mm, that's a decent plan, but MAKE SURE not to try and do this with 3.5mm - 3.5mm TRS cables because, invariably, they'll get in with the rest of your patchcords and then when you NEED them, well... But at a pinch, you could use unbalanced TS cables, but that's sort of a kludge with certain drawbacks of its own. But as for the headphone-to-modular preamp idea...don't. Headphone signals are hotter than line-level, which is what the Ladik's expecting. A better idea for getting the Hydra in with other signals would be to run a small stereo mixer, connect all of the toys you want to run through the modular on that, then send the mixer's out to the Ladik inputs. Convenient and simple!

Balanced signals always have 3 leads. Balanced signals on XLR cables are pretty simple. XLR cables can carry balanced mic or line level signals. It's "balanced" as it's a low impedance signal that's great for longer distances. But it gets around the additional interference by being able to mathematically subtract out any external interference at the receiving end.

On 1/4" cable, it'll use TIP-RING-SLEEVE cables (three leads). Your typical guitar or unbalanced 1/4" only has two leads (tip-sleeve). You might also know the tip-ring-sleeve set-up as "stereo". But I'm avoiding using that description as it just conflates unbalanced stereo signals with balanced mono signals... even though they are ran over the same connectors. (please double check your cables for impedance if you're running balance signals over them. You don't want to use a high impedance three conductor cable, especially over a longer length of cable.

Most prosumer mixers and other gear will have balanced connections on 1/4" jacks in order to save space and cost.

So yes, to run balanced audio between two devices, you need to start with 3 leads and END with 3 leads at its destination... and of course, both send and receive have to have balanced outputs and inputs. Check the manual.

Cables are not balanced because it is low impedance, they're balanced because the audio signal and the inverted phase copy sent on the 2 live wires can be recombined in such a way to cancel out any noise that has been picked up on the cable!

Cables are not balanced because it is low impedance, they're balanced because the audio signal and the inverted phase copy sent on the 2 live wires can be recombined in such a way to cancel out any noise that has been picked up on the cable!
-- JimHowell1970

Well, Jim, I'm trying to keep it light rather than making a 40 page treatise on balanced power. I think you have it backwards there. Low impedance cables have to be balanced. Balancing is used to mitigate the inherent short comings of low impedance signals (subjected to noise). The biggest ADVANTAGE of low impedance is minimal loss (relatively) of high frequencies that long runs of high impedance impart on the signal.

The idea is that the braided cable will be equally affected by an interference. The high and low signal are phase inverted. For example if you want to transmit a signal that at that instance is +3volts, a +3 volt signal will be sent on the positive and a -3 volt signal (inverted) will be sent on the negative. The absolute difference is 6V. Divide that by two and you get the original +3 volts.The same for the inverse -3 volts minus +3 volts equals -6 volts divided by 2 equals -3 volts.

When interference hits both the positive and negative leads it doesn't change the results. (+3volts +1 volt (noise)) - (-3volts +1 volt (noise))/2 still equals +3volts if you do the maths... no pun intended.

Well, Ronin1973, I did look it up,before I posted

https://www.aviom.com/blog/balanced-vs-unbalanced/

But I might be wrong!

EDITED Oct 13th 2021, 22:37