From Brian Willoughby Sent Fri, Jan 4th 2019, 05:47
On Dec 28, 2018, at 11:01 AM, Mark Spano <xxxxxxxxxxx@xxxxx.xxx> wrote: > I think somewhat simply, you should look through the documentation for = your gear and parse for the word "unity". If you can find it in regards = to signal flow and gain staging, it should illuminate the way. The ideal = is to have all gear connected to each other, passing signal along = between each other at "unity" gain. That is, no added or removed = amplification other than maintaining its nominal level. A lot of gear = won't have this information, and then you kind of have to gauge it = yourself. In those cases, I would play a pure (sine, triangle, etc.) = tone, and adjust for 0 VU / -20 dBFs on output, and see if you can land = that same level on input to the incoming piece of gear. That gives you = decent level going out, accounting for enough headroom for additive = tones and manipulation without clipping. This is good advice, but it might be more difficult than you think. * That pure sine or pure triangle will be quieter than other patches = with more going on. Different wave shapes might produce high = peak-to-peak voltages than other wave shapes. If you have a two = oscillator or three oscillator synth, then you really should crank up = all of the oscillators in the synth=E2=80=99s pre-filter mixer to = determine the maximum patch output level. If you have a polyphonic = synth, then you should endeavor to play full chords that engage all = voices. If you have velocity assigned to level, then you=E2=80=99ll want = to set levels against maximum velocity. If you want your studio setup to = be =E2=80=9Cset and forget=E2=80=9D then you have a lot of work to do up = front. * Even with all oscillators cranked up to full volume, there might be = still more headroom beyond that if you set the VCF to extreme resonance = and find a particular frequency that aligns oscillator and filter. Since = this sort of signal path might occur in some of your synth patches, you = probably want to make sure that your output volume knob and mixer input = trim are set to avoid distortion for maximum resonance. * Some filters reduce gain with resonance, others do not. This makes it = more difficult to find the maximum output. * If there are any effects on your synth, that adds another dimension of = level variations to deal with. Some effects add a lot of noise, too. * Finally, the concept of unity and nominal levels only makes sense for = mixers and devices that have a standard output level (like a CD player = or a tape deck). A synthesizer does not fall into this category. There = is no unity level on a synth, because there is no standard level. Every = synth has a different power supply voltage, and thus the waveforms have = different levels. I=E2=80=99ve looked at synth schematics where some = waveforms use the full bipolar supply for peak-to-peak levels, while = other waveforms only use the positive supply, and thus are 6 dB quieter. = Even the CD player broke from the standard for audio electronics that = came before, because they wanted to increase the signal-to-noise ratio. = But synths have no standard output level, so you can=E2=80=99t really = say what is nominal, what is low, and what is high. Adjusting for -20 = dBFS might not be the best choice. Targeting -18 dBFS or even -12 dBFS = might make more sense. If you actually can reliably determine the = maximum level that your synth can output, then you might as well set the = channel for -d dBFS or even -3 dBFS. * The concept of unity might be useful, though, if you can find out = about the final circuits in your synth. Some synths might have a lot of = gain in the final output stage, and so you will probably get better = results if you leave that final stage at unity instead of boosting the = volume drastically. Other synths have nothing but attenuation at the = final stage, so you might do best there by leaving the master volume = knob at maximum. It really depends upon the synth. * My experience with older MOTU interfaces is that they have gain, but = not attenuation. If that=E2=80=99s true of the 828 mk3 and/or 8pre, then = the synth master volume will have to be turned down to avoid clipping. Brian Willoughby