Question About Volume Controls

[BAA]

Is the "0" point on a volume control a standard reference point? by this I mean does it represent the volume level you would expect to encounter at a live performance, or does it represent some other reference point or is it arbitrarily picked by equipment manufacturers? Or other still....

 

[zumbo]

http://www.rane.com/par-d.html#decibel

 

[MDS]

0dB on a receiver volume control is a standard reference point only in the sense that it is standard to use that point for your 'reference' level.

As far as what it actually corresponds to in terms of the electrical characteristics of the receiver, there is no standard and it is essentially an arbitrary point chosen by the manufacturer. It might be the point at which the receiver is putting out its rated power, it might be the point that is 80% of rated power, it might be the point where the output meets the rated distortion level, it might be the point where the pre-outs would output the maximum signal level they are capable of (say 1V). It could be any of those things and there is no way to know because the manufacturers don't tell us, but in general, it is totally arbitary and meaningless.

Now as far as what 0dB means in terms of a digital signal, that is well defined. 0dB FS (full scale) is the highest level the signal can achieve. It relates to the number of bits that was used when quantizing the signal. Thus for 16 bit PCM (like a CD) 0dB is a sample value of +32,767 or -32,768 [remember a waveform has both a positive and negative component].

 

[sjdgpt]

0dB on a receiver volume control is a standard reference point only in the sense that it is standard to use that point for your 'reference' level.

As far as what it actually corresponds to in terms of the electrical characteristics of the receiver, there is no standard and it is essentially an arbitrary point chosen by the manufacturer. It might be the point at which the receiver is putting out its rated power, it might be the point that is 80% of rated power, it might be the point where the output meets the rated distortion level, it might be the point where the pre-outs would output the maximum signal level they are capable of (say 1V). It could be any of those things and there is no way to know because the manufacturers don't tell us, but in general, it is totally arbitary and meaningless.

Now as far as what 0dB means in terms of a digital signal, that is well defined. 0dB FS (full scale) is the highest level the signal can achieve. It relates to the number of bits that was used when quantizing the signal. Thus for 16 bit PCM (like a CD) 0dB is a sample value of +32,767 or -32,768 [remember a waveform has both a positive and negative component].

Sounds good to me.

A follow up question(s).

Since we can crank the volume past the "0" point, I have always assumed that the value must have a legitimate purpose. Maybe only meaningful to the manufacturer, such as a specific voltage output (as you said, the preamp stage), but then why list the number for the consumer? Why not just have meaningless number scale of 1 to 100. Of for the "my system is louder than your system" crowd, use 1 to 1000.

And is the output number that is displayed, let's say -40db (a nice setting on my system for watching a movie at 2AM without anybody else having to hear it), actually 40db below the "0" point?

When I read the owners manual to the Denon 2805, it states the volume adjustment is in 0.5db increments. I must wonder about my superior hearing, because I can clearly discern the difference between -39db and -40db, and I think I can hear the 0.5 difference as well.

 

[MDS]

Some receivers do use a scale from 0 to X, generally termed 'absolute' volume display as opposed to 'relative' (-infinity to +whatever). Onkyo states in their manuals that 0dB on the relative scale corresponds to 82 on the absolute scale.

The scale on one receiver is not comparable to the scale on another, which is why you can't compare receivers by what number on the volume scale achieves the loudness you desire (LOTS of posts like that on every forum I read and participate in - my old XXX was loud at 50 but I have to turn up the new one to 65 to get the same level...).

The scale is meaningless until you calibrate to a specific level and thus have a concrete output SPL level. If you calibrate to a level of say 75dB at 0 on the volume scale, then -10 does have meaning because it means your ouput SPL will be 10dB below 75dB (or 5 dB for the Denon that says volume increments are .5dB). If you haven't calibrated to a known level, then simply saying I listen at -40 means absolutely nothing unless you know what that number means in terms of the receiver's electrical characteristics (and they don't tell us as I said before). I think THX certified receivers do have a specific output at 0dB, but I don't know what the spec calls for.

So in short, volume scales are meaningless until you calibrate to a known level. If two receivers are calibrated to the same level, then they can be directly compared, but the number on the scale is still meaningless. For example, I have my Onkyo 502 calibrated to 75dB at 60 on the volume scale (it uses absolute 0 - 80). If you calibrate the Denon to 75dB at 0, then the two are putting out the same SPL. If you then play the Denon at -10, you are listening at 5dB below your 'reference' of 75dB (if it does use .5dB increments/decrements). If I play the Onkyo at 55, then I am also listening at 5dB below reference. Because we both used the same reference, the output is identical.

 

[sjdgpt]

(or 5 dB for the Denon that says volume increments are .5dB

The display is in 0.5db, they dont actually say what the increments are... just display in 0.5db.