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  #1  
Old Nov 17th, 2010, 01:52 AM
holo holo is offline
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Default Fixed or Variable volume control

Hi

I have the following sonos gear. A Cullen modded Sonos ZP90 and it is in a Peachtree Nova which I will connect to my Yamaha 3900 reciever which is obviously connected to my speakers. I also have an S5 elsewhere in the house.

As I have been renovating my house I only have a temporary setup, however this finishes soon and I will get all my gear out.

So, if I set the volume at fixed volume this means I control the volume just through my receiver remote control. However it means the volume buttons on the cr200 and iPhones don't work.

Alternatively, if i set it to variable volume, I need ensure the receiver is at a sufficient volume to start with, and then I can control the Sonos volume from the cr200 or iPhones.

So, variable volume is perhaps more convenient, as 3 devices control the volume.

However, I seem to recall fixed volume produces the best sound. Is this correct ?

Do you use fixed or variable sound settings ?

Thanks
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  #2  
Old Nov 17th, 2010, 03:14 AM
buzz buzz is offline
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holo,

Functionally, what is the benefit of the Nova?

The digital outputs of the ZP90 use a 24-bit volume control. If you keep the ZP90's volume out of the lowest settings, discussions of sonic "damage" become very academic.

Operationally, I recommend using an automated speaker selector and a ZP120 for the main room. This avoids the volume control(s) "war".
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  #3  
Old Nov 17th, 2010, 03:33 AM
the_lhc the_lhc is offline
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Quote:
Originally Posted by buzz View Post
holo,

Functionally, what is the benefit of the Nova?
It's a digital integrated amplifier and it has a hole in the back of it which can accept a ZP-90 (or 80).
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  #4  
Old Nov 17th, 2010, 05:33 AM
ninjabob ninjabob is offline
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My understanding is that if you do not use variable volume without a reasonable overhead then ReplayGain does not work so I use variable with my AVR350.
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  #5  
Old Nov 17th, 2010, 01:02 PM
holo holo is offline
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Quote:
Originally Posted by the_lhc View Post
It's a digital integrated amplifier and it has a hole in the back of it which can accept a ZP-90 (or 80).

yep, and a very good dac as well.

http://signalpathint.com/index.php/Nova/Nova.html

So, the thought is that there is no loss of sound quality with variable sound output ?
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  #6  
Old Nov 17th, 2010, 01:53 PM
ratty ratty is offline
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Quote:
Originally Posted by holo View Post
So, the thought is that there is no loss of sound quality with variable sound output ?
Until you drop the variable volume to a very low level, there should be no loss of resolution. The ZP volume control operates in 24-bits and populates the lowest byte on the S/PDIF as the volume reduces from maximum.

This thread might make for interesting reading.

I've not seen confirmation of whether any dithering is applied during volume adjustment.
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  #7  
Old Nov 17th, 2010, 02:40 PM
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Majik Majik is offline
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Quote:
Originally Posted by holo View Post
So, the thought is that there is no loss of sound quality with variable sound output ?
It's not a straightforward answer.

(Long and rambling discussion follows):

There's two different, but related, things to consider: the fidelity of the digital data, and the impact in the analogue domain.

Considering the digital data, reducing the volume means changing the data. This is fundamental. You are changing the amplitude of the samples. Let's look at some examples assuming a 16-bit word

A sample with a value of 0010000000000000 in binary (8,192 in decimal) should end up as 0001000000000000 (4,096 decimal) for a gain reduction of 50%.

However, a sample with a value of 0010000000000001 in binary (8,193 decimal) will also end up as 0001000000000000 (4,096 decimal) with the 50% volume reduction. As you can see, there's an error here. This is because the resolution of the 16-bit word isn't enough to capture the detail of the original data in after the gain reduction.

Now, consider if the word length is 24-bits. In this case we have 8 bits of greater resolution. Our second sample can now be represented as:
001000000000000000000000
in binary (with the original 16-bit data in bold). This allows us to do the 50% gain reduction to get:
000100000000000010000000
You can see the original bits are preserved, meaning the error is less.

This is what Sonos does with fixed volume: adjusts the amplitude of a 16-bit sample within a 24-bit word so as to not have to discard the data.

Note that these bits (like the one I have underlined) represent tiny differences in volume level between samples. The further to the right they go, the smaller the effect they have.

Eventually if you turn the volume down, the bits start falling off the end of even a 24-bit word. This happens when the volume is set at of below -48dB down from the "fully on" level, which is pretty low. By most standards this is considered "mute".

The other thing to consider is that, just with any kind of maths, there can be rounding errors introduced by the fact that the numbering system cannot accurately represent every possible number.

This is basically a precision issue, just as before.

Consider how a pocket calculator represents 1/3 as 0.33333333. In reality the 3's go on forever but the calculator cannot represent them all. It has limited precision. 0.33333333 is very close to 1/3 but it's not exactly the same. There is an error there which is caused by the limitations of the decimal numbering system. The greater the precision you can represent the number, the smaller the error.

The same thing happens with binary. With 24-bits, the rounding error is very small (+/-144dB).

The other thing to then consider is what the impact of this is when converted to analogue at the DAC. All DACs (and their supporting circuitry) have a noise floor below which effectively limits the useful resolution of the system. If you have a noise floor of -96dB, that effectively limits the useful resolution of the system to around 16-bits. If you feed such a system with 24-bits then any data in the lower 8-bits is lost in the noise.

So although with the Sonos digital volume control you don't lose bits, what you are doing is moving the signal further into the noise floor of the DAC. Depending on the DAC you have, and your environment, etc. this may or may not be an issue for you.

Bear in mind every follow-on component in the system, including the listening environment itself, contributes noise which has a similar masking effect to the DAC noise floor. Even if you are using an analogue volume control, turning it it down will move the signal further into the noise floor of the amplifier. Also, as analogue volume controls are typically an active part of the audio chain, unless they are very high quality they can introduce significant noise themselves.

So, the answer really is, Your Mileage May Vary depending on your system, your environment, your ears, and your brain.

Much has been made of the "negative" impacts of using digital volume control, but these claims are often made ignoring the equivalent impacts of analogue controls.

The reality is any differences are very, very, very small. There may be people who can hear them, but in tests most people cannot hear the differences between high-quality MP3s and lossless files. The differences between analogue and digital controls are normally far less than this.

If you have a high-end system and worry about hearing the potential differences enough to spoil your enjoyment of the music then go with fixed volume and use your amp analogue volume control (if, indeed, it is analogue) to control the volume.

If you are happy with the sound you are getting, then use the Sonos volume control and get the benefit of the convenience (not to mention Replaygain will work if you use it).

Cheers,

Keith
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I am not affiliated with or representative of Sonos in any way. All opinions expressed are my own!

Last edited by Majik; Nov 17th, 2010 at 02:54 PM.
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  #8  
Old Nov 19th, 2010, 12:15 AM
holo holo is offline
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thanks ratty and Keith, when I get my proper gear set up in a week or so I look forward to experimenting a bit. Volume control with iPhone/iPad is so convenient though
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  #9  
Old Nov 19th, 2010, 01:25 AM
biggetje biggetje is offline
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I use variable volume output on my ZP90.
ZP is connected to ADM9.1 active speakers.

I put the volume setting of the ADM's such, that if the CR200 is set to max. volume, the system volume output will be the maximum that is still enjoyable for me and the neighbors ;-)

The ADM's are able to reproduce very, very little details in music, but I was not able to hear any difference in fix- or variable setting.
Theory may be different, but this is how I experience it.


Note: with "little details" of course I mean "a lot of details" ;-)

Last edited by biggetje; Nov 20th, 2010 at 12:22 PM.
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  #10  
Old Nov 19th, 2010, 02:05 AM
ratty ratty is offline
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Quote:
Originally Posted by biggetje View Post
The ADM's are able to reproduce very, very little details in music, but I was not able to hear any difference in fix- or variable setting.
The ADMs support 24-bits on the S/PDIF and, in-theory, in the DAC. How much effective resolution they have I don't know, but their noise floor is excellent. I've not heard differences between Variable and Fixed either.

I actually run a ZP80 at Fixed Volume into my ADM9s. They're in a room which is rarely linked with other zones, I consciously want to defeat ReplayGain for album play and I appreciate the very fine resolution of the ADMs own volume control. Each to his own.
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