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View Full Version : Does the Squeezebox's volume adjustment affect sound quality?



Triggaaar
2005-08-29, 03:47
I understand that when using the digital output, I should fix the Digital output level in the Audio section of player settings, in order to achieve maximum quality.

But when using the analogue outputs, should I turn the Squeezebox's volume to maximum, and then use the amp to adjust volume from there? (I'm not set-up enough to start doing blind tests yet)

Thanks

julian2002
2005-08-29, 06:32
(very) simply put the squeezebox's volume control works by loosing bits - the lower the volume the less bits used - as the dac is 24 bit there is a bit of leeway but you'll be losing low level detail below a certain threshold. if you are after ultimate fidelity then you should use your amps volume control.

luuk
2005-08-29, 13:11
Please explain in a little more detail how the volume control works by losing bits and why it should be set to full volume in order to preserve quality. Does this apply to analogue and digital outputs?

julian2002
2005-08-29, 16:11
again very basicly.
a digital audio signal is basicly a number between 0 and 65535 the higher the number the louder the sound. in order to attenuate the volume this number must be reduced. if you have a signal of say 3
which is represented as: 0011 in binary
and you attenuate it by, say, a factor of 4 then you effectively run out of bits to represent the resulting fractional number (as cd players use integer maths) and therefore you lose the detail represented by these 'low' bits.
if you have a 16 bit data source and a 24 bit dac then the '3' read from the disc can be represented as: 001100000000
you have 8 extra 'low' bits that the previously missing data can be shifted into so attenuating by 4 now gives you: 000011000000
but go too low and you still run out of bits.
unfortunately it's not always this simple as those extra low bits on a 24 bit dac can also be used for other stuff like dithering and upsampling which can complicate things.

MrC
2005-08-29, 17:40
For the non-bits/bytes oriented folks, i hope this little physical analogy is useful.

You know those toys that have hundreds or thousands of metal pins in a grid, that you can make impressions of your face, or hand. You push something into the grid of pins, and the impression is formed of whatever you placed there, positive image on one side, negative image on the other.

Lowering the volume is not unlike uniformly pushing the other side to reset the device - slowly you start to lose the definition because each of the pins is being pushed back towards the flat position. Pretty soon, you can longer make out the impression, eventually going to completely flat.

luuk
2005-08-30, 12:05
Let's see if I have understood it all (-: Am I right in thinkin g that if I turn the volume up completely on the SB2 and then take it down a little, this is not likely to influence the quality very much or even at all. However, if I have thye volume set at the lowest and then increase it there will be a marked increase in quality?

Thanks a heap, particularly for the analogy. I shall have to read up a bit on the actual bits and bytes.

Jim Holtz
2005-08-30, 19:59
Here's a link to Audio Circle and a post by Wayne regarding how the SB2 handles the digital volume in comparison to other high end audiophile electronics.

Jim

SB2 rocks! :-)

http://www.audiocircle.com/circles/viewtopic.php?p=188459#188459