Digital ouput and volume.....

  • 13 January 2007
  • 31 replies
  • 9360 views

I have been away from the forum for a while, but am still looking forward to getting a SONOS. :)

I have a question about the digital output and the SONOS volume control. HOw do they interact? I plan for an outboard DAC, and I would like to connect it straight to an amplifer without any kind of preamp if I can get away with it.....is this recommended? Or does the volume control effect the digital signal adversely?

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31 replies

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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.

---

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!
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.
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
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).
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
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! 😉
[ ... ]
This also doesn't take into account what I've heard, that turning down the Sonos volume from 100% to 70% or 80% does not lose any data... so (if that were true - appreciate people who can clear up this myth/fact) you could conceivably set your Sonos vol to 80, then set the pre-amp volume, and then have the headroom to turn up or down the volume...?


At 100% volume the digital stream is passed through without modification. Bit for Bit, whatever was ripped from the CD will be presented to your DAC.

In order to decrease the volume, since SONOS can't control the follow on equipment, the ZP80 must change the digital code.

Your scheme of setting the normal room volume using the follow on equipment, with the ZP80 set to max, will remove the possibility of any signal loss for regular critical listening. While distracted, you won't care as much about any (small) degredation introduced by the digital volume control.

---

It's easy to fuss with this issue. Start by being gross with things. Set the ZP80 for a very low volume, then increase the volume control setting of the follow on equipment. This will give you a feel for what could happen at the worst end of things. (don't forget to use the digital output)

Next, flip things the other way. Set the ZP80 near the top end of its volume control and listen at the same level as before by adjusting the follow on equipment.

Finally, set the ZP80 for maximum, listen for a while, then back off a notch or two using the ZP80's control. Always take care to keep the same listening level in the room. Some listeners will care about the quality difference and some won't.

At this point feel qualified to form your own opinion (it's the only opinion that matters). Just because an "expert" somewhere says that "everyone" can hear the "HUGE" difference, doesn't make it so. In my opinion there is also a difference between perceiving a difference and caring about it.
Userlevel 2
John-

But what Buzz is saying is that any decrease of the zp volume less than 100% degrades the digital signal your DAC is getting. You, therefore, would want line out fixed or 100% and never change volume on zp- only use volume control on preamp.



For me, the increase in sound quality is worth the outboard dac. I generally (during a given listening session) only turn down the volume or mute... So for me, it's a matter of just being able to have downward/off control. I don't need to be able to crank it up. In other words, I'll set my baseline volume at the pre-amp (no remote for me - I'm a purist), and if someone wants me to engage in a conversation, I'll turn down the Sonos Controller vol. In other words, for me, the only time that I might want to turn down the vol, I'm already distracted anyhow!

This also doesn't take into account what I've heard, that turning down the Sonos volume from 100% to 70% or 80% does not lose any data... so (if that were true - appreciate people who can clear up this myth/fact) you could conceivably set your Sonos vol to 80, then set the pre-amp volume, and then have the headroom to turn up or down the volume...?

Thoughts?

J
To wrap up the first part of this thread:

If you have high impedence speakers that need a high current to drive them effectively, your choices for high-end audio are:


Probably just a typo, but low impedance speakers require more current.

---

And a note to correct a possible misconception hinted by other posters:

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

My comments about the noise and possible frequency response variations created by analog volume controls, while easily measurable, usually result in very subtile changes in the audible result unless one of the units is poorly designed or you are using too much or the wrong cable.

More gain may give a feeling of more power because things get loud with a small rotation of the volume control. Some volume controls have a gentle "taper," the relation between rotation and output, at the low end. This allows more precise control at the lower end and it causes lots of complaints from users who upgrade from a low class unit. The low class units often have a rather abrupt jump in volume at the low end. The usual complaint is that "all I had to do with the old unit was 'crack' the volume control and it blew me out of the room. With the new unit I must turn it up half way." The new unit could have several times the power of the old unit, but there is often a strong psychological connection between small rotation and power. (Perhaps this is an American thing because European units typically have a more gentle taper.)
John-

But what Buzz is saying is that any decrease of the zp volume less than 100% degrades the digital signal your DAC is getting. You, therefore, would want line out fixed or 100% and never change volume on zp- only use volume control on preamp.

This is what I want to avoid, yet have super-convenient instant music on and zp volume control only to mess with and a high current amp to drive really inefficient Totem Acoustic speakers.

I'd rather have digital conversion by Sonos and zp's volume control over outboard dac and two remotes in my hand (and waiting for power up and switching source to blah, blah blah).
Userlevel 2


3. Zp80 line out straight to amp and use convenient volume control.

I'd like to go the #3 route, if available.


Ditto. I'm not averse to using a pre-amp in between (because of active amplification in pre-amp from ~1.7V up to 20-30V), setting the ZP volume to 100 at the highest volume I'm likely to use for that listening session, and then using the ZP control just to back down/mute the vol when needed... So I think for me, the solution will be:

ZP80->DAC->Pre-Amp->Power Amp

Setting the ZP80 vol to variable, but leaving it on 100, adjusting the pre-amp volume to the max I'm likely to need, then adjusting volume for that listening session with the ZP80.

How else do y'all do it? Is there *any* difference between variable volume with volume=100% and fixed volume?

Thanks,
J
To wrap up the first part of this thread:

If you have high impedence speakers that need a high current to drive them effectively, your choices for high-end audio are:

1. Zp80 digitally / external or use internal DAC / PreAmp / Amp and lose the inconvenience of the Zp's volume control.

2. Zp80 line out fixed / preamp / amp. Lose convenience of volume control on controller.

3. Zp80 line out straight to amp and use convenient volume control.

I'd like to go the #3 route, if available.
Userlevel 2
Pch,

I tried a few of the tracks that I pointed you to, but I haven't ripped any of my own.

You'll want to split the AC3 track from the DVD.

Basically you are on your own, and since part of this process involves bypassing the DVD's encryption, We won't discuss the exact process here.


OK, so you can't help me?
And Buzz, I understand that we could not discuss the entire method overhere because of the DVD copy protection! That's why I wanted it via pm...
And I know that I need the AC3 track from the DVD, the question is how, with which program?
Pity you won't/can't help me, because I really would like to stream the 5.1 DTS/DD-tracks of my own (highly paid for!!!) DVD's with the Sonos when this is possible.

Gr. Paul.
Pch,

I tried a few of the tracks that I pointed you to, but I haven't ripped any of my own.

You'll want to split the AC3 track from the DVD.

Basically you are on your own, and since part of this process involves bypassing the DVD's encryption, We won't discuss the exact process here.
Userlevel 2
Pch,

Searching for "DVD sound track extraction" will turn up a long list of interesting websites.


I did a search on Google and downloaded:
-DVD Audio extractor
-DVD Smartripper
-DVD2AVI
-DVD Audio Ripper (new one)
-DG Index
-DVD to WAV converter
I tried for almost 5 (!) hours, but with no results...
Buzz, can you please help me and tell me what program you use and what the steps are you follow...Once I heard 5.1 thrue Sonos ZP-80 I want all my dvd's om my NAS so I can stream them with the Sonos!:D

Gr. Paul.
Pch,

Searching for "DVD sound track extraction" will turn up a long list of interesting websites.
Userlevel 2

You will probably enjoy these clips.


Buzz, I downloaded a file and it works:
the sound is AMAZING!!!:D
I would like to have this with all my music-dvd's, can that be done with special software?
Please p.m. me.

Gr. Paul.
Userlevel 2

You can't stuff a complete DVD into the ZP80, only the audio track and this "audio" must be at 44.1KHz.

But is this "audio" DTS/DD 5.1 or just PCM 2.0?



I've been able to pass DTS streams to a surround decoder.

You may experience a few clicks and pops while the DAC switches formats.

Buzz, exactly how did you do that?
(you may answer this by p.m. if it is not allowed to name programs on the forum.)

Gr. Paul.
Pch,

Maybe I could have worded that better.

You can't stuff a complete DVD into the ZP80, only the audio track and this "audio" must be at 44.1KHz.

---

I haven't tried this, but I suppose that anything that looks like a valid audio file will be passed, but if the bitrate is not supported by SONOS, the results will not be happy.

I've been able to pass DTS streams to a surround decoder.

You may experience a few clicks and pops while the DAC switches formats.
Userlevel 2
Pch,

If you manipulate the Dolby Digital or DTS track so that it becomes a lossless 44.1Khz audio track, the ZP80 will pass it through the digital outputs (at fixed or full volume).

Since the Dolby Digital and DTS streams are already compressed, there is very little advantage in wrapping the file in a lossless compression format.

You will probably enjoy these clips.


Buzz, wait a minute...
I thought I could really play a DTS/DD-stream with the Sonos, and that my Classé would recognize it as a DTS/DD-stream and would process it so I would get real 5.1-surround sound.
But what I understand now is that you 1st "manipulate" it? Is that the same I did with "DVD AudioRipper"? But then you get a 44.1 khz audiotrack like you said which is definitely NOT DTS/DD anymore, right?
Or am I missing something here?

Gr. Paul.
Pch,

If you manipulate the Dolby Digital or DTS track so that it becomes a lossless 44.1Khz audio track, the ZP80 will pass it through the digital outputs (at fixed or full volume).

Since the Dolby Digital and DTS streams are already compressed, there is very little advantage in wrapping the file in a lossless compression format.

You will probably enjoy these clips.
Userlevel 2
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.


Buzz, is this a fact? Can I stream a DTS/DD-soundtrack from a dvd with the Sonos ZP-80? That would be great! 🙂
I do have the Classé SSP-30 and the Sonos ZP-80. Can I really get the DTS/DD-soundtrack in a folder? How do I do that? I know how to rip and copy a dvd, do I have to use the audio.ts now instead of the video.ts?
When I have a good music-dvd what I do now is this: rip it to the HDD, then make a WAV out of it with "AudioRipper", then in iTunes I convert it to AAC 320kbps.
A bit complex, isn't it?
It would be great to have the full DTS/DD-soundtrack available with the Sonos and the Classé homecinema system.
I do understand that I have to fix the volume....

Gr. Paul.
Yes, it's amazing what high gain at the input of a power amp gives you...sounds like you got a good preamp!
Userlevel 2
I have now added a high end preamp, Electrocompaniet EC 4.7 MK2, with 16 volt outoput, balanced (XLR) signal.

Its a huuuuuge different in the power of the ZP80 signal and the EC 4.7 preamp signal. With ZP80 i used to play with 75% volume, With the preamp i only use 25%!

It sounds like the music got more POWER and more/deeper bass. 🙂
A volume control is simply a resistor with a fixed contact at each end and a moving contact attached to the knob. A line level signal is applied across the ends with the "low" end connected to ground. When the volume control is at minimum, the "wiper" is effectively connected to ground and there is no output signal. At maximum volume the wiper is connected directly to the line in.

At mid rotation there is resistance between the wiper and ground and to line in. Part of this resistance is effectively in series between the line in and the volume control output.

Meanwhile, the cable has some capacitance. At higher frequencies, the capacitor begins to act as a low resistance shunt to ground. This high frequency shunt, combined with the series restance of the mid rotation control, begins to roll off the highs.

At maximum volume the low impedance line in swamps the cable capacitance and the highs return.

But wait, there is another drama: Since it is not at a temperature of absolute zero, every resistor is actually a noise generator. The noise voltage increases with temperature and resistance.

Returning to our volume control, when we are at minimum, the output is connected to ground, there is very little resistance and a very low noise voltage. At maximum rotation the outrput is connected to the low impedance line in and the noise voltage is both absorbed by the line in and swamped by the large signal. At mid rotation, the output noise is passed to the follow-on device.

Hence, there is a point near mid rotation of our passive volume control that maximizes noise and minimizes the high frequency response.

These effects are very easy to measure and often are not so hard to hear.

---

The following experiment does not work on well designed equipment or units with electronic volume controls.

Insert a shorting plug into a line level input and switch to this input. In a VERY quiet room, rotate the volume control through its entire range while listening close to the speakers or with headphones. Surprise!! there is an increase in noise as the control is rotated through its center range.

Equipment reviewers are well aware of this little quirk. That's why they measure noise and frequency response at a preamp's full volume. (but they forgot to tell you exactly why they do that -- the numbers look better)