Audio module has attenuation?

I thought I noticed Rack was quieter when first trying v2 but I assumed it must have been my imagination. However, I’ve just come across a situation where the patch sounds fine when playing but when I recorded it through the NYSTHI recorder it is overloaded and distorted. Looking at some meters I’m a bit confused about what is happening.

Bass Master shows levels above zero and so does AS meter and NYSTHI recorder but the Audio device shows it not even getting very close to zero.

Why is this?

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It depends on what is used as reference for 0dB by the module makers. Rack’s standard says that 0dB corresponds to ±10V, but some find it better to use ±5V for the 0dB reference.

In MixMaster, we use ±5V for 0dB in all VU meters except the master VU (which uses ±10V). VCV Recorder and Audio2 use ±10V. In BassMaster though, since that module can be aimed at tracks or put on the master output, we have a menu option to scale the VU as tracks (±5V) or as master (±10V).

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Could you add the option to have the master VU in ±5V? I don’t know what the arguments are for either option but ±5V seems more intuitive to me and more indicative of whether something is too hot.

But that aside why is it not distorted when I play the patch but is when I record it?

Unfortunately I don’t think we will be adding any more features to the MixMaster, it’s already quite full in its menus, and we think that ±5V = 0dB is not really something suited to the master VU.

For your issue though, perhaps it could be that there are very short transient levels that go beyond ±10V and that your audio device handles them gracefully, while the recorder does not? Just guessing here, but maybe with a VCV Scope you can spot if the max/min voltages go beyond that range. One thing that is for sure, you should ideally never have anything in your audio go beyond ±10V in Rack when your signals get near the outputs (Audio out, recorders, etc).

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It’s exactly as it should be, but let’s just say that the official standard for voltage and gainstaging in Rack is not universally understood, and so e.g. you have VU meters showing… something, but you don’t really know what it is. The Mindmeld mixer does it exactly right.

So, here’s the official standard, from the horses mouth:

https://vcvrack.com/manual/VoltageStandards#Levels

Signals should typically be 10V_{pp}10Vpp​ (peak-to-peak). This means that audio outputs should typically be ±5V (before bandlimiting is applied), and CV modulation sources should typically be 0 to 10V (unipolar CV) or ±5V (bipolar CV).

Absolute decibel measurements (e.g. for VU meters) should be relative to 10V amplitude. For example, a ±10V signal is 0 dB, and a ±5V signal is approximately -6 dB. You may alternatively use dBV for measurements relative to 1V amplitude.

In other words: What should go out to your audio module (and hence, your audio interface) or your recorder is a max. signal strength of +/- 10V (20 V/peak2peak), and what a single soundsource in Rack, say an oscillator, should deliver is a signal strength of +/- 5V (10 V/peak2peak). And that’s it.

So, you can’t as an example use a VU meter that shows 0db=+/- 5V right before your audio module, it’s the wrong signal level and you’ll get confused. Short version: Just use mindmeld or VCV modules. Long version: Find the VU meters that are calibrated for the right level at the right points in your signal chain.

When I worked for a certain DAW make I was always arguing that our mixers should have 0 db at like 18 db below clipping. There’s no need to run signals so hot these days! Give yourself some headroom.

I think the often used “k system” metering uses 12, 14, and 20 db below clipping as users selectable definitions of “0”.

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I don’t really understand the reasoning for preferring what it is at the moment. A master VU should show you if something is going to clip on export and the current implementation doesn’t sometimes.

Another example, mindmeld master and audio device show only occasional clipping but there is significant clipping going on with recording.

@Squinky I was wondering if this was something like showing RMS or K system vs Peak but the -+5 vs -+10 seems like an arbitrarily different beast?

I think there are multiple viewpoints on that, but yeah, master at the output, sure, I’ll buy that. I think my choice would be something consistent everywhere, and I would pick -18, as long as there was a clipping or peak indicator somewhere.

Oh sure, I’m just relaying what the official levels are. For your own production techniques you’ll settle at what ever level works for mixing and mastering, given your other gear, propensities for watching meters etc. But at least there’s an official standard in Rack to be aware of, that the various audio modules are designed for.

What current implementation? What modules? You keep throwing all these different VU meters together and I’ve pointed out why that will confuse you, because some of them are not showing the same thing/what you think they’re showing.

Here, try this: Use the VCV Recorder, record some audio, and whilst doing it watch that its meter at all times stays below 0db but gets close to it. Then import the .wav file into audacity and observe that the level is perfect - i.e. never clips and uses the bandwidth to the max. In other words: Works as it should.

By the way, the question of “what’s the right level to record at” entirely depends on who/what the receiver is, doesn’t it? I mean - “don’t clip” is always right, but going to vinyl? One level. Going to YouTube? Another level. Going to downloadable MP3? Another level. Going to Spotify? Another level. They all have either physical requirements (e.g. vinyl) or have set specific LUFS levels to not exceed, to curb the loudnes-wars and keep things sounding reasonably levelled from track to track.

There’s the nice Loudness Penalty service and plugin, that’ll show you the right level if you want to go to all those services with one recording: https://www.loudnesspenalty.com/

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The MindMeld mixer will absolutely show you if it is going to clip on export. The master bus has both hard clip and soft clip modes. In hard clip mode, the moment you go above 0dB on the master you are clipping. In soft clip mode you have another 1.6dB or so above 0dB iirc before hard clipping occurs. But if you follow the rule that you don’t go above 0dB on the master (and the master VU does not turn red) then there should be no clipping in your recording.

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The NYSTHI recorder is very sensitive, but it has options in the right-click-menu to attenuate the signal.

I think the -6dB option worked for me to get 0dB on the recorder being the same as 0dB on the output channel of the soundcard.

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on the Master Recorder you should check always the PEAK meters not the RMS meters

If they are RED, you are clipping

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agreed, there are a lot of different meters in Rack, and a VU meter is almost certainly not what you what for this situation.

It doesn’t help that many of the meters are vague as to what they are actually doing, and very few of those labeled as VU meters are actually showing VU at all.

So make some calibrated meters, please! Preferably supporting as many standards as possible :wink:

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Hear hear! Would love a good meter that could show regular metering, true peak, and the 3 relevant LUFS values, something like that.

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