Digital ouput and volume.....

  • 13 January 2007
  • 31 replies
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31 replies

Userlevel 2
Simply adding gain does not accomplish much in terms of improving sound.

Buzz, I respectfully and strongly disagree with this statement. Come on over to my house and I'll setup a demo for ya! 😉
Buzz, I respectfully and strongly disagree with this statement. Come on over to my house and I'll setup a demo for ya! ;)

I'm not much fun at one of those parties. Here on the forums I'm docile, but at a showdown party I'm the worst grump that you can imagine. All that I try to do is keep things honest while everyone else is trying to show that their dog is the best.

In my opinion a lot of the "magic" happens while the cables are swaped around and the connections are accidently cleaned.

So many subtile variables can influence the outcome of one of these showdowns. Stereo stores use those silly A/B switches and you always need to hold the switch down for "B". They all know that "B" is a little harder and the tension of holding the button down gives "A" a few points. You are taught to arrange the demo such that the speaker the salesperson wants to sell is on "A". (in my experience even if "A" and "B" are identical, listeners will pick "A" at a 60/40 to 70/30 rate)

Anyway, I'll continue to claim that gain is neutral. Unfortunately, adding a box that introduces more or less gain changes other aspects of the system that could easily result in changing the sound. I'm not saying that you didn't hear and appreciate a difference or that I could or could not do the same, but I don't want to attribute that difference to "gain".
Userlevel 2
Anyway, I'll continue to claim that gain is neutral. Unfortunately, adding a box that introduces more or less gain changes other aspects of the system that could easily result in changing the sound. I'm not saying that you didn't hear and appreciate a difference or that I could or could not do the same, but I don't want to attribute that difference to "gain".

Buzz, I think I understand what you're saying but just to clarify... It's been shown that even small differences in gain will make the "loudest" component sound best. In particular, there have been double blind comparisons done where the same component was sampled with very small differences in gain (the listeners thinking they where hearing different amps or whatever). The correlation between slightly higher gain and higher preference was good even for very small differences in gain, though I can't recall what differences where involved off the top of my head (I think it was like .5dB or some such thing).
Peter Hunsberger,

Yes, 0.5dB is more than enough level difference to sway a comparison.

In the context of this discussion "gain" is a simple multiplier of the signal. Done properly, changing the gain of a unit will not significantly change the noise, distortion, or frequency response of a system. Many controls marked as "Volume" controls are simple gain controls, while others are loudness controls. Loudness controls fuss with the frequency response in a hopefully constructive way (given how our auditory perception works).

As far as I am concerned, adding another box invalidates earlier comparisons, even if the box claims only to add gain. (gain can be greater or less than unity) With the added box comes added connections and the possibility of an unintended contribution to the outcome.

It is surprisingly difficult to make valid "goodness of sound" comparisons. A very small level difference, a smile or approving grunt from a respected member of the listening panel, the "tension" of operating a volume control higher than you expecIt, or knowing that box xyz costs several times more than box zzz, can easily poison the honesty of the test.

Recent exposure of the listener to loud noises effects the results too. I discourage critical listening if the subject has been in a car, plane, train, or bus in the past few hours.
Userlevel 2
Just my humble opinion -
My circuit consists of
- NAD C372 Integrated Amp (150 watts)
- April Music Stello DA100 DAC (upsampling to 192Khz)
- Monitor Audio Sliver RS 6 speakers (6ohm)
- HSU Research VTF-2 Mk3 downfiring subwoofer (250 watts)
- ZP80 connected to DAC via TOSLINK optical cable (mid-range Monster THX-certified)
- Buffalo Terastation (1TB) RAID 5 config (connected directly to ZP80)
- 100MB network

Other components:
Polk XM Receiver (Digital Coax to DAC)
Onkyo CD Changer (TOSLINK to DAC)

All audio files encoded in FLAC (Compression Level 😎 with Replay Gain

Best sound for me is using Fixed Volume mode. Was using Variable but noticed distortion at higher volume levels. Not scientific, just my ears telling me something was not quite right. Other sources did not exprience same symptom. Once I switched the ZP80 to fixed volume the results were on par with the other sources. If you are concerned with sound quality over convenience try this type of configuration.
Badge
Audiophiliac,

At full volume or fixed output SONOS passes the digital stream unmodified. While it makes little sense to any analog units, the ZP80 digital connection will pass a DTS or Dolby Digital stream through to a digital input.

When you lower the volume, the digital stream must be modified. This will destroy the DTS and Dolby Digital signal, because the bit stream is modified and is no longer a valid DTS or Dolby Digital stream. With enough processor power, the streams could be decoded and rebuilt with lower volume levels, but since this is a stereo audio device, there is no point in adding that expense.

For the stereo audio signal, since we have a fixed number of bits to play with, some of the bits must be thrown away as the volume is lowered. Gradually, as the volume is lowered, the lower level information will be lost.

Which digital amplifier are you using? I'm not familiar with any digital power amplifiers amplifiers that don't have some sort of input level control.

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In the analog world, lowering the volume is not so hard on the music. The lower level information is gradually buried in the noise as the volume level is decreased. In the digital domain, the least significant bits are simply dropped. It would be possible to ease the digital degredation by use of "dither", but I don't know if SONOS is using this method.


This is really helpful!

Do you know how the volume control works in a typical Sonos speaker or the Sonos Amp?
I guess the question is best described using the Sonos Amp (but applies to the Sonos speakers too - the Amp is effectively a combination of a simple amplifier and a Sonos Connect. When you change the volume via the Spotify app for example, does this control the volume of the digital stream (so the equivalent of the Sonos Connect in this example), or does it control the analog amplifier output (so the simple amplifier in this example)?
Thanks in advance!

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