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[phusis]

Hi all --

I'm happily using JRiver MC19 for music and Blu-ray playback. My D/A Converter is a NuForce DAC-9 (w/24-bit DAC chip, from what I know) coupled directly to a Belles SA-30 poweramp, and the internal volume control of MC19 is used. ASIO is the chosen output mode.

Now my question goes:

Via the 'Audio Path' I can see the output is 32-bit, but how can that be when my DAC's maximum bit depth (I suppose; the DAC chip used is a Burr-Brown PCM1798) is 24-bit? EDIT: is it a "true" 32-bit output evenso - that is, with regard to the available bit-range of the digital volume control of MC19? 

Being that I use the internal volume control the max. supported output bit depth is very much of interest here, so to get a heading on when bit truncation could become an issue. With 24-bit output (of which only roughly 21-22 bits are effectively available?) it is my understanding 16-bit source material can take up to about 36dB (or less) of attenuation before being affected, while 24-bit material is impacted, it would seem, even at 0dB. Here a true 32-bit output would be a blessing, needless to say - certainly with 16-bit material, although 24-bit material could face truncation at <36dB in a similar fashion as a 16-bit source with 24-bit output.

Furthermore: how much does a dithered volume control  help here - i.e.: where truncation is involved?

[6233638]

You get about 6dB per bit, so if we're talking about the digital domain, that gives you about 48dB of attenuation if you're playing 16-bit audio at 24-bit.
 
It gets quite complicated once you get out of the digital domain and start considering what the actual noise floor of your DAC is (20-bit would be very good performance, and state-of-the-art is in the 21-22 bit range) and beyond that, there's the noise floor of your amplifier, which will be higher still - most will measure closer to 16-bit performance than 20-bit.
 
The short version is: unless you're actually hearing a problem, it's best not to worry about it.
 
One thing you might be able to do is to use a lower wattage amplifier, or a passive attenuator between the DAC and amplifier so that the digital volume control is closer to 100% when it's at normal listening levels, if that's something you are concerned about.
 
Personally, I think these issues are over-exaggerated on a lot of audio forums.
 
 
 
As for Media Center's output being 32-bit when you only have a 24-bit DAC, I'm guessing that you are using an ASIO driver, as ASIO only works in 32-bit - at least that is my understanding.

There is an option under Tools > Options > Audio > Device Settings which lets you specify that the DAC only uses 24-bit data when using an ASIO output.
 
This should only really affect the noise shaping used, and shouldn't really have much of an audible effect whether it's enabled or not. It's more about being technically correct than being something you really need to be concerned about.
 
 
There is a bit-depth simulator available in the parametric EQ DSP which you can use to hear the effect of reducing the bit-depth at its extremes.
When you're actually playing music, you can probably reduce the bit-depth quite a lot before the effects are made audible.

[phusis]

6233638 --

Thanks for your fast and informative reply!

Mostly my concern revolves around playback of 24-bit material and how this is always affected with 24-bit output (in effect, it would seem, with somewhat less than 24 usable bits..), such that a theoretical concern at least would see diminishment where true 32-bit output was available. I have in fact been in some flaming forum-discussions on the use of digital volume controls, where I have tried to address the importance of having actual experience with proper digital attenuation before forming theory-heavy conclusions on their claimed non-merits (the constant "loss of resolution, etc. etc." babble, without even seeing "inwards" the inherent limitations of analog dittos), so I'm really an outspoken proponent of digital attenuation. The implemention of dithering in MC's internal control volume certainly made a possitive difference to an already excellent device.

My poweramp is in the low power end already, specified at 30 watts pure class A, but my speakers are fairly efficient so I rarely get much below 35dB of attenuation (except with down-converted 2-channel Blu-ray playback). I don't detect any audible problems with MC's digital colume control per se, but oftentimes what can better doesn't dawn on you until actually hearing it (as in: "I thought everything was A-OK, but dammit if is this new developement doesn't lift the sonic potential even further"). A passive attenuator has been considered, but given the present sonic state I don't much feel inclined towards its implementation (alas: though of course I could be wrong). I guess the coming of a true 32-bit DAC (not that these aren't available as is) would quiet any concern most effectively..

Thanks again for your reply.

[6233638]

Well a 32-bit DAC would certainly be better if you want to attenuate the volume of a 24-bit track in the digital domain, as you can do so without discarding any information.
 
But no 32-bit DAC comes close to 32-bits on its analog output - as I said before, the state of the art does not quite approach 22-bits, and at that stage we're really getting limited by thermal noise more than anything else.
 
 
It's another case where it is theoretically better to use 32-bits, but practically I don't think it's going to make any difference whatsoever.
Whatever difference there may be, will be masked by the noise floor of either the DAC's analog output, or your amplifier's noise floor.
 
You would be much more likely to hear a difference from better matching your DAC's output to the amplifier, so that you don't have to use as much digital volume attenuation in the first place.

[Vincent Kars]

The DACs by ESS are 32 bit.
Indeed this is about volume control without losing resolution.
They have a nice paper about it:
http://www.esstech.com/PDF/digital-vs-analog-volume-control.pdf

[6233638]

Actually, the ESS DACs have 48-bit internal precision for things like volume control.
Many of the devices these DAC chips are used in will only accept 24-bit inputs though.

[kstuart]

FYI, Schiit Bifrost and Gungnir DACs are entirely 32-bit internally.

Their included ASIO driver works best when set to "32-bit" regardless of the file being played.

[kstuart]

When you're actually playing music, you can probably reduce the bit-depth quite a lot before the effects are made audible.

You do realize that this is exactly the same statement as "madVR provides both BiCubic and Jinc scaling, but the difference is not visually detectable in watching videos" ?

[mojave]

A couple of clarifications:

ASIO only works in 32-bit - at least that is my understanding

I have two Steinberg pro audio DACS with ASIO drivers (both still on the market). One has a 32-bit internal audio path and one has a 24-bit internal audio path. I also have several consumer audio cards and it differs. It is completely up to the device/driver whether it will use 24 or 32-bit. However, most are 32-bit. The only way to know is to check the audio path output.

Their included ASIO driver works best when set to "32-bit" regardless of the file being played.

If using JRiver's internal volume control and the DAC has 24-bit final output, then in the device settings (Tools > Options > Audio > Audio Device > Device Settings) you want to check the box "Device uses only most significant 24-bits (Lynx, etc.). This is so JRiver applies the proper dither to 24-bit rather than 32-bit. You can read more in this thread.

The DACs by ESS are 32 bit.
Indeed this is about volume control without losing resolution.
They have a nice paper about it:

What is funny about that presentation is it is using the ESS9008S DAC. On page 14 of the presentation, it shows that the DAC has 24-bit output. So the internal 32-bit processing still is dithered to 24-bits at the end. In this case it is actually better to use JRiver's 64-bit volume control for more precision through the DSP and not use the ESS volume control. The newer ESS DAC's do have 32-bit output.

[phusis]

Thanks to all for inputs.

A couple of clarifications:
I have two Steinberg pro audio DACS with ASIO drivers (both still on the market). One has a 32-bit internal audio path and one has a 24-bit internal audio path. I also have several consumer audio cards and it differs. It is completely up to the device/driver whether it will use 24 or 32-bit. However, most are 32-bit. The only way to know is to check the audio path output.
If using JRiver's internal volume control and the DAC has 24-bit final output, then in the device settings (Tools > Options > Audio > Audio Device > Device Settings) you want to check the box "Device uses only most significant 24-bits (Lynx, etc.). This is so JRiver applies the proper dither to 24-bit rather than 32-bit. You can read more in this thread.
What is funny about that presentation is it is using the ESS9008S DAC. On page 14 of the presentation, it shows that the DAC has 24-bit output. So the internal 32-bit processing still is dithered to 24-bits at the end. In this case it is actually better to use JRiver's 64-bit volume control for more precision through the DSP and not use the ESS volume control. The newer ESS DAC's do have 32-bit output.

mojave --

I've followed your (boldfaced) advice, but for some reason finds the sonic outcome in the wake of this to be a mixed blessing - indeed restrictive. Generally the presentation feels less vibrant as if lacking a natural reverberance.

Maybe the fact that I'm using a USB to S/PDIF converter, the Audiophilleo2 + PurePower, via the BNC input of my DAC has something to do with this?

[kstuart]

Again, Schiit advises that their DACs are internally 32-bit throughout, and so not to apply the boldfaced advice above.   (And their own ASIO driver setting should also be 32-bit for best sound quality.)

Note that this has nothing to do with the bit depth of files that will be played through the DAC.

You might want to inquire specifically with your equipment manufacturers.

[6233638]

Again, Schiit advises that their DACs are internally 32-bit throughout, and so not to apply the boldfaced advice above.   (And their own ASIO driver setting should also be 32-bit for best sound quality.)

I'm not sure why you keep bringing this up, as phusis has a 24-bit NuForce DAC-9.

[kstuart]

I'm not sure why you keep bringing this up, as phusis has a 24-bit NuForce DAC-9.

Because mojave quoted my previous text about that, when he replied mentioning the "device uses the most significant bits" checkbox.

And I wanted to clarify that I asked about that specific point.

JRiver support in Interact is designed so that threads are used by later readers as sources of information, so I wanted to make it clear that the checkbox should not be checked unless one is certain that it applies.

By quoting my text about a 32-bit DAC, mojave may have inadvertently confused the issue (by implying that the checkbox is helpful or needed most of the time, when it is not).