XX volume control - something weird going on

[manisandher]

I've just discovered something really weird with the XX volume control...

For the last couple of weeks I've had my old Pass Labs X1 preamp present in my office system because I've been playing around with loads of different components. The messing around with components ended yesterday evening, but I was too lazy to take the preamp out of the chain. So I set XX to 0dB and had music in the background as I worked. I was quite shocked at the audible clipping in so much of the modern pop music I tried (the loudness wars really have gotten totally out of hand). In the past I would have switched PeakExtend on, but last night I just turned the XX volume to -1.5dB. Of course, the audible clipping stopped, but I was shocked in the change in the overall sound.

At 0dB, the sound is thick, full, and pretty boring. At -1.5dB (and any greater attenuation setting thereafter), the sound immediately comes to life. And I'm now talking about well-recorded stuff, well below clipping level.

Peter, there is something really strange going on. There simply shouldn't be such a big difference between 0dB and any other volume setting (assuming no clipping).

Mani.

[PeterSt]

Hi Mani,

You could try normal Arc Prediction, assumed that you use a Custom Filter setting.
Difference ?

You aren't using Volume Normalisation ?

Peter

[manisandher]

Yes, I was using the Custom Filter (705600 Low). But I can hear the same effect with AP too - maybe slightly more difficult to hear because there is more 'sparkle' with AP anyway, so the 'dullness' at 0dB is somewhat compensated for.

I've never tried Volume Normalisation.

Mani.

[manisandher]

On further listening...

On many tracks, I actually prefer the 0dB setting - there's way more energy in the upper-bass/lower-mid area, which gives a fuller, fatter sound. With 'thin' recordings, this is very welcome. But if the recording is already very 'thick' sounding, 0dB just makes it sound too boring.

But the point remains that there is a very big difference in sound between 0dB and any other attenuation setting, and I don't think there should be.

Mani.

[PeterSt]

Mani,

Maybe by now you have forgotton the quite some posts throughout time about sweetspots and such of the D/A chips. I'd even say that about everyone using a pre-amp (which are not many people in the first place) does not use the -0dBFS setting (but 6dB or so less). So, all as expected.
Btw, the real sweetspot is at -21dBFS or so.

As long as your mentioned "clipping" is not that at all, all is fine. Or "normal" if you want.

Btw, technically you shift the used bits in the D/A chips, assumed that you can not hear (perceive) the full dynamic range of 144dB. So say that you(r ears) use 96dB of dynamic range maximum, then at -0dBFS you use the upper 16 bits, and at -6dBFS the next batch of 16 bits (say 17 MSB's with the first one not in use). And so on.
Of course you can only really notice a difference when first the music utilizes the full scale (say continuously).

Peter

[manisandher]

But music is dynamic, so you're never going to be in the sweet spot for very much of the time, irrespective of where you set the attenuation, right?

All I can say is that I have now tried a whole bunch of tracks with RMS levels ranging from -30dBFS to -8dBFS (according to TT-DR meter) and changing the XX attenuation from 0dB to -1.5dB has exactly the same effect on SQ on all of them.

Coincidence, or what?

Mani.

[PeterSt]

You talk like albums/tracks with an RMS level of -30dBFS play only up to that level. They will play into the MSB just the same.
Albums which never exceed -6dBFS can be counted on two fingers (and then I even make one up).

Peter

[manisandher]

You can judge from the first few seconds of various tracks, some of which never go about -20dBFS.

I know what I'm hearing... 0dB sounds totally different to any other attenuation level.

Mani.

[manisandher]

BTW, I've just compared a few tracks with quiet beginnings in 3 ways:

1. XX set to 0dB, preamp set to 11
2. XX set to -1.5dB, preamp set to 12
3. XX set to -21dB, preamp set to 23

There is a slight difference between 2 and 3. There is a massive difference between 1 and 2/3. Something is going on...

Mani.

[PeterSt]

I don't have a pre-amp.

[PeterSt]

What about the combination -0dBFS / 12 ?
(no, I am not joking)

[manisandher]

Yep, the change in SQ is still easily audible:

-1.5dB/12 sounds like -1.5dB/11, just a little louder.

0dB/12 sounds like 0dB/11, just a little louder.

Do you want me to get my ADC out again???

Mani.

[PeterSt]

Mani,

Do you want me to get my ADC out again???

Well, I have been thinking what we could do with the gear you have. I was thinking about something without microphone. And your ADC would be right that ...

Use this test tone :

1000Hz test file

and play at -0dBFS and at -1.5dBFS.

I am not sure how to calibrate the recording level but I think the only importance is that you don't record too loud. So be low 20dB to be on the safe side, is no problem.

The signal itself is at -3dBFS.

Peter

[PeterSt]

I forgot ! ...

... and send the result to me.
Recording of a few seconds only is sufficient. Make it 10 or so.

Peter

[manisandher]

Will do later today...

But I was also thinking of simply making two 10 second recordings of a track where the effect is pronounced, one at 0dB the other at -1.5dB. You could match volumes at your end and take a listen - as long as you're not at 0dB, you should hear what I'm hearing, no?

But I'll start with your test.

Mani.