[jpelg]

How do you vary volume via a digital output without playing with bits?

 

[helluvapixel]

Quote:

How do you vary volume via a digital output without playing with bits?

it reads a line signal. so your system knows what 'volume level' the bits get convert to audio should play. Everything will require a line level. That's why some DACs sound better with some amps because they have  high line level etc. The bits are intact, there's just a line level bit attached to the stream so a volume can be established.

 

[davebtw]

Hello,
 
That means somewhere in the chain there is gain/loss being applied:  If it is in the digital domain then the bits are being changed, if in the analog domain, that is a different story.  I am using a Benchmark DAC-1 as my converter, and I assure you there is a gain control in the digital path.  That means the bits are being changed.  Of course if it is a small amount, then it may be benign.
 
I just wondered what others here on this forum know about the issue.  I have the equipment and will be measuring the thing very soon and I'll report here what I find.  It won't be hard to tell what is going on, once I get my Audio Precision on the thing.
 
I was hoping it worked like my discman or a regular CD player with a digital output.  No volume control in the digital path on any unit I have ever owned.
 
-david BTW
 
 

 

[Skylab]

So are you guys saying the volume control still works in the digital domain when you are running the Pure into a DAC?  I didn't try that, but I doubt that would work.  I bet it is just a volume control when you are using the Pure's analog outs.  In which case, if you leave it at full volume, and control the volume with your preamp/headphone amp, you are fine (that is what I did when I tested it).

 

[BmWr75]

Exactly.....just like you should do with iTunes.  Always leave the volume control at maximum in iTunes if you want an unadulterated digital signal for wireless streaming (this comment applies only to PCs running XP or earlier, am unsure if Windows 7 solved this problem).

 

[helluvapixel]

Quote:

So are you guys saying the volume control still works in the digital domain when you are running the Pure into a DAC? 

You can control volume on the digital out. From what I read elsewhere your best bet is to ensure the volume is 100%.
 
However, because you are still sending the same musical bits is adjusting the volume, hence a line level adjustment, really altering the digital sound you'd hear? I mean, if the digital is carrying the sound of a guitar chord "C", it's a sound chord "C" by any measure of the volume or loudness. Aren't we into some level of semantics here, since all output devices have a line level of some sort. Not all DACs send the same line level (volume).
 
If there is bad quality in the recording, adjusting a volume from the digital output won't change that. Nor if it's a good recording would it change? The issue is more providing the clean signal at the correct level so not to introduce distortion/clipping?
 

 

[grokit]

Not using an i20, but on my high power rig I leave my dual mono speaker amp volume pots in a fixed position and attenuate in iTunes, there's no difference in SQ that I can hear whether it's at 100% or not but I'm using a Mac.

 

[helluvapixel]

http://www.hydrogenaudio.org/forums/index.php?showtopic=47597&view=findpost&p=422892
 
I found this post interesting. A bit subjective but possibly in the truest sense there is 'some' change to the bits but whether it adversely affects audio..... anyways I sent PURE an email to see what their official line is on the matter.

 

[jpelg]

It is my (admittedly VERY limited) understanding that digital volume attenuation can have issues, with its effectiveness & resultant sound quality being highly dependent on the specific implementation. 

 

[zzffnn]

I am using iPhone 3GS streaming 320 kbps MOG -> Pure i20 -> Gamma2 Dac -> Beta 22 -> LCD-2s / PK1. The digital volume control does not work in this case (the screen says "no volume available").
However, with using the iPod function of iPhone 3GS in the exact same setting, the digital volume DOES work.
No big deal for me as I do not care that much for a digital transport that cost only $100; at that price, it is a good deal (I can even streaming youtube video to TV using i20!).

 

[helluvapixel]

I am going to confirm that using an iPhone 3GS has no volume control (on analog output). To date I've been using a 160GB iPod Classic (volume control on analog and digital output).

 

[grokit]

I would love to read a comparison between the i20 used as an iPod transport and some of the usb-spdif converters out there like the Bravo, Hiface, and MHDT Bridge being used with iTunes.

 

[zzffnn]

No. What I said was that 3GS streaming MOG.com has no vloume control, which has to do with MOG.com or streaming.
But, using the iPod funtion of 3GS playing songs stored in 3GS, I DO HAVE digital volume control when feeding i20 to a dac.
I do not care for i20's analog output so I have not tested that.

 
Quote:

I am going to confirm that using an iPhone 3GS has no volume control (on analog output). To date I've been using a 160GB iPod Classic (volume control on analog and digital output).

 
 

 

[davebtw]

I sent in a tech support request to Pure and after some back and forth trying to find the right words so the tech support engineer got the real question I today received this really pretty clear answer:
 
Dear David,

The maximum volume control setting on i20 sets 0dBfs digital output level within the DSP which converts asynchronous USB packetized audio data from the iPod to I2S audio data (i20 system) to feed the D/A converter within i20 and also to feed the digital outputs (S/P-Dif).

This can be quickly verified with a digitally generated file of -nndBfs added to the iPod playlist and then played out of the S/P-DIF path on i20 and digitally captured, as digital interfaces pass level in absolute dBfs with 0dBfs being the highest magnitude signal that can be described.

N.B. Additionally, yes, using the digital volume control at a setting other than 0dBfs (maximum) does manipulate the audio stream to reduce volume and hence with large shifts (SNR)

Regards,
 
David Wilson
 
 
I will be confirming this with real measurements when I get my lab (and Audio Precision System Two Cascade) rebuilt in the very near future.  In the meantime, it appears that once the iPhone4 is on the doc, running up the volume to full using the i20 remote will provide the best digital output, with the most dynamic range and maybe even bit-accurate when using apple lossless format(we shall see).  There is no indication that the volume control is going up or down on the screen, so one just has to keep hitting the up command until convinced it is up all the way.
 
Have Fun,
 
-david BTW
 

 

[.Sup]

Interesting. The volume on Onkyo dock has no effect if its on low or high volume.