# bogaudio analyzer vs span: why this difference in db?

Same signal, one on span, one on bogaudio analyzer:

It seems span is around -38db, while bogaudio analyzer around -24. Why?

Try a higher quality on the analyzer.

Still way different:

(notice the higher peak). Maybe @matt can clarify this?

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very strange: 3 analyzers, 3 different peak levels

ā¦ but at the end, all that matters is the sound to my ears

Db itself is always a relative number. You need to specify what 0 means to make it absolute. You will find the same thing withVU meters. This is not surprising at all. oh, Sry, didnāt intend to respond to @Ahornberg - just responding to post.

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There was a discussion on this topic, see Query about decibels and the voltage standard

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ah, I had forgotten there is a standard. and, btw, Ā± 10V is not 20v, itās 10. for peak that is.

Huh?

I guess the confusion stems from the definition of sine wave amplitude. Some measure the displacement from 0 (I guess what your are calling peak amplitude), whereas others measure peak to peak. I prefer peak to peak because it implicitly forces you to compensate for DC offset. If measuring displacement from 0, a naĆÆve person might mistakenly assign a 10V peak amplitude for a unipolar 0-10 signal, and 5V peak amplitude for bipolar +/- 5. But they have the same peak amplitude of 5V - the unipolar 0 point is 5V.

Measuring peak to peak seems more obvious / intuitive from a language perspective. I immediately know I must compute (max - min) to get the the correct peak to peak amplitude of 10V.

The phrase āpeak amplitudeā sounds too much like āpeak to peakā, which I think leads to a lot of confusion.

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oh, sure enough, you are correct. I did not know that! actually, I think my statement was technically correct, +/- 10 does seem to be called ā10v peakā. But none the less, I did not know the definition of āpeak to peakā.

Not really sure about this dB its relative to common value in Rack. As explained by Vortico here, 10V is 0db and 5V is -6.02 db.

In fact, if I feed a basic Sine (2khz) to scope and Span, it works as expected:

Why on bogaudio analyzer is 0db?

On MixMaster mix, there are even both

On single channel 0db, on Master -6dbā¦

By design :-). We figured 10V=0dB (which is the standard) would be good for the master (when soft-clipping is off technically, but almost the same when itās on), but that 5V=0dB would be more appropriate for the tracks.

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So, VCV proposes a VCV standard, not everyone follows it. Either intentionally to make a better product, or unintentionally because it doesnāt matter to most people. Is that really so difficult to believe?

Yes, I just find it very weird (even more within the same plugin) But I can seeā¦

Thanks

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As squinky says, dB is a relative rather than absolute value - it depends on what voltage the developer decides 0dB is.

Oscillators (mostly) output +/- 5V by default. It made sense to us to make that 0db on the tracks on MM. It also means tracks have some headroom (ie room for user error) built in - a track on MM wonāt actually clip until it hits +6dB. Most users who donāt fully understand all this level stuff will probably presume under 0dB is āgoodā and over 0dB is ābadā.

The Audio module on the other hand expects +/- 10V. It therefore made sense for the Master on MM which connects to that to also be calibrated such that 10V = 0dB. If you go above 0dB on the master on MM, your audio will clip - you donāt get any extra headroom there (other than the soft clipping). But thatās one stereo bus you need to keep a careful eye on rather than 16 different tracksā¦

If MM tracks were calibrated such that 10V = 0db (rather than 5V = 0dB as they are) everyone would need to learn to mix each track to -6dB max and we would probably be responsible for thousands of clipped/ruined audio recordingsā¦

All this is explained in the manual btw. As Marc said - it was a considered design choice at the time and 5 years later, Iād make the same choice again today.

We were not the first mixer to take this approach btw - iirc the Msc Hack mixer that came before MM did the same.

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Absolutely! Given that that is actually the Rack voltage standards itās the only thing that makes sense, IMHO (but always open to learn).

Which is what 90% of the producers does (i.e. mix tracks at -6db), more or less Its a common choice to mix below 0db on each track, due to headroom.

Thatās why basically (I believe) all DAW Iāve used have the same reference in both tracks/sends and master.