#826

update on my previous statement: it works…sort of.

audio has worked seamlessly. I’ve had a few tiny hiccups on occasion, but I think they came from somewhere else in my chain.

however, every time that my macbook is closed and goes to sleep with the ultralite on, it crashes my laptop. so I have to shut down my mk4 before I close my laptop. or deal with the crashes.

not ideal, but livable enough assuming it’s a short-term thing.

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#827

Thank you for taking your time to elaborate on these!

#828

Im planning on repurposing my a&h zed10fx (which was mainly my pa mixer back when there were gigs) to use with my modular…has anyone done this and are there any concerns about modular levels damaging the line ins? Im sure i can attenuate on the way in, just wondering about whats the ‘worst case’ and might i fry my channels.

#829

cool. thanks for the feedback.

#830

Yup, I’ve used that mixer with my modular. Works just fine, altho I always use attenuators on the way out for any mixer I’m using. I like the Pittsburgh mixers that double as attenuators. Also always a useful additional stage for dialing in additional control of saturation to the mic preamp stages. No worries about damaging anything that I’ve ever encountered, but maybe there’s something I don’t know.

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#831

The spec sheet for the ZED-10FX says it accepts up to +31dBu on the line inputs, which is just shy of 78 volts peak-peak - so unless you’ve got some very odd modules you should be OK.

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#832

To add to that, most modular systems use ±12V or ±15V supplies, so anything they generate or process will be clipped to well under 24Vpp or 30Vpp inside the system in any case.

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#833

Is frying mixer/soundcard inputs with too hot signals really a thing that happens? I get that maybe if you put a full scale modular output into a small battery powered consumer speaker it might have problems, but I see a lot of people say to be careful but I don’t hear many stories of bad things actually happening to pro or semipro gear.

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#834

In my experience, most semi-pro / pro level mixers and audio interfaces I’ve used that are specced to work with around +4 dBu nominal levels handle modular audio levels just fine with zero to minimal attenuation. The not-so-professional ones designed for smaller nominal levels and little headroom (eg. many portable consumer devices) simply clip pretty badly unless you attenuate.

I haven’t yet seen or heard anyone blow up a mixer or audio interface input by feeding it too loud signal from a modular synth yet. Which doesn’t mean it couldn’t happen - just that considering the amount of interfaces and modular systems me and people I know have used without worry, it’s bound to be a pretty rare accident due to less than foolproof design of the mixer’s / interface’s input stage, I suppose.

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#835

thanks everyone for the responses! into the loop goes the zed.

#836

Anyone have any good resources to understand the relationship between volts, dB, dBu, and volume? I feel like I have some basics, but something to firm up my understanding would help a lot.

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#837

In short:

  • Volts: measure of difference in electrical potential between two points. If only one point is referenced, the other point is the “ground” signal, which is treated as the reference and is treated as 0V.
  • dB: a way to express the ratio between two quantities. When measuring amplitudes (including volts), it is 20 * log₁₀ (v₁/v₂). So if one amplitude is 20db relative to another, then it is 10x as big. An amplitude that is twice as large is ~6db larger.
  • dBV: a dB measure of voltage relative to 1 volt. So 0dBV means a signal that is 1V. -10dBV means a signal that is 0.3162 volts.
  • dBu: a dB measure of voltage relative to 0.7746 volts (!). So a 0dBu means a signal that is 0.7746 volts, +4dBu means a signal that is 1.228 volts.

Notes:

  • all the voltage measures above are RMS - because AC signals vary, we need to agree on how to measure them. “Peak to peak” measure, for a sine wave, will be bigger by √2. (Wave forms with the same peak to peak measure will have different RMS values. RMS is a better measure of the total energy in the waveform.)
  • Every 6db amplitude is closely 2x the amplitude of the signal. It is roughly perceived as a bit less than twice as loud. Perceptual loudness is complicated, but this is an okay approximation.
  • There is 11.782 db difference in the reference level for consumer gear (-10dBV) and professional gear (+4dBu). That’s a lot!
  • A 5 V peak-to-peak sine wave from your modular, is ~3.5V RMS… which is 13dBu - so more than 9dB above reference level. This is why eurorack level is so “hot”. Some modules can produce signals as hot as 10 V p-to-p, which would be even hotter.
  • The problem with putting a pro level signal into consumer gear, or modular signal into pro gear is that if the peak-to-peak voltage exceeds the headroom of the device (the amount of voltage over the reference voltage it can accept) - and then things start to clip. Remember that peak-to-peak is always more than RMS, and dBV and dBu are w.r.t. RMS. — Headroom varies considerably from device to device, though as a rule professional level gear has more headroom than consumer. This is why you can put your modular into a pro-level mixer and it’s okay so long as you lower the faders to match other signals.

Quick read:

Good calculator:
https://www.analog.com/en/design-center/interactive-design-tools/dbconvert.html#

Updated: incorporated @kbra’s notes & some minor editing

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#838

Just to underline a bit from the great overview:

  1. As mentioned, -10 dBV and +4 dBu are reference or “typical” levels that the gear is expected to output / handle without making a sweat. Practically all mixers, audio interfaces etc. are designed so that you will need a lot louder signal to actually make them clip or overload (headroom). Eg. the previous example of a relatively small and inexpensive A&H mixer that accepts inputs up to +31dBu.

  2. Although there is no official standard everyone would follow (if you don’t count Doepfer tech notes which nobody follows very strictly, not even Doepfer), nominal Eurorack audio signal levels are somewhere around ±5V or 10Vpp. That means roughly 3.54V RMS or a bit under +13.2dBu. In theory the modules can produce ±10V or 20Vpp signals, and you sort of have to be prepared that it won’t blow anything up. But they rarely do - unipolar CV signals that peak at +8V or +10V aren’t very rare but most of the time they stay inside the system for practical reasons.

(Other modular systems have their own nominal levels of course, eg. I think Buchla 200e audio signal levels are close to normal professional line levels so you’ll have even less worries with them.)

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