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Ideal audio output level from Chromecast to DAC?

lattiboy

lattiboy

Well-Known Member
Hey there,

I have a Musical Fidelity VDAC II that I feed my main system with. I use a Chromecast with an HDMI optical audio extractor as my source (I've done A/B between this setup and a Chromecast Audio with optical out and found no difference)

At any rate, I stream TIDAL HiFi to the system with my iPhone and was wondering what the output level in the app should be. I had assumed about 50 percent, but then an engineer friend said you should always have it at full volume if using optical output to an external DAC.

Can somebody chime in on this?

thanks!
 
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Anybody else? I hear a bit of noise floor while at 100%, but I don't know if that's the amp or pre....
 
Isn't the output a digital signal, not processed yet? I would think that the attenuator would have no effect.

BillWojo
 
It is variable in the digital domain. I feel the Chromecast is pretty loud in the analog output compared to my DAC set to 0dB. I just swapped to optical but haven’t used it much since getting a Bluesound Vault 2i. I will compare that with my DAC and report back.
 
Btw, optical out of CCA is 24 bits, at least when I'm streaming Sporify, and it is volume-controlled.
 
So, what you're really asking about is the volume on the app on your iPhone, correct? If so, I'd say 90% is good. But, just use what sounds good to you and your system.
 
lattiboy said:
Hey there,

I have a Musical Fidelity VDAC II that I feed my main system with. I use a Chromecast with an HDMI optical audio extractor as my source (I've done A/B between this setup and a Chromecast Audio with optical out and found no difference)

At any rate, I stream TIDAL HiFi to the system with my iPhone and was wondering what the output level in the app should be. I had assumed about 50 percent, but then an engineer friend said you should always have it at full volume if using optical output to an external DAC.

Can somebody chime in on this?

thanks!
Click to expand...

If loudness at the head end is being digitally attenuated, then you are shaving off resolution to do so. Typically one or two bits. You are better off setting loudness to ‘off’, ‘fixed at 100%’, or whatever full output setting will disable digital loudness attenuation. You will get better resolution attenuating loudness in the later analog stages by doing so.
 
^^^ Not necessarily, 16 bits can be attenuated in the 24 bit space with no resoulution loss until way down, this is what happens in Chromecast Audio I suspect.
 
Late to the party, I know. This caught my eye: "I use a Chromecast with an HDMI optical audio extractor as my source." What is an "HDMI optical audio extractor?"
 
Calypte said:
Late to the party, I know. This caught my eye: "I use a Chromecast with an HDMI optical audio extractor as my source." What is an "HDMI optical audio extractor?"
Click to expand...

It’s a cheap device that separates out the optical steam from an hdmi device. The output has optical and hdmi which lets you use older AVR
 
PAGS said:
I like to adjust the volume with my tablet, so obviously I don't do 100%. But I'm an audio cretin.
Click to expand...

Ha ha. I’m definitely an audio cretin then. I’m listening to Spotify premium streaming from my iPad as I type this on my iPad and going through my CCA. I set the volume on my amp to a level that gives me some wiggle room to adjust on the tablet or iPhone. Bits, attenuation, meh. I’ve not noticed any difference in SQ, especially since it’s not hires.
 
lattiboy said:
It’s a cheap device that "separates out the optical steam" from an hdmi device.
Click to expand...

Yes, it`s a cheap device, but no, it does not separate a optical signal from the HDMI signal stream, because there isn`t any optical in the HDMI signal, but, it does, in fact, sample off the HDMI digital audio stream, and then converts/transcodes the signal to S/PDIF optical &, or Coax..

My quotation marks added to attiboy`s post..

Just saying, so there won`t be any confusion..

Kind regards, Billy Ferris
 
jcg1112 said:
Ha ha. I’m definitely an audio cretin then. I’m listening to Spotify premium streaming from my iPad as I type this on my iPad and going through my CCA. I set the volume on my amp to a level that gives me some wiggle room to adjust on the tablet or iPhone. Bits, attenuation, meh. I’ve not noticed any difference in SQ, especially since it’s not hires.
Click to expand...

The volume is actually controlled on the CCA in 24 or 32 bits, that's why there's no SQ loss.
 
gvl said:
The volume is actually controlled on the CCA in 24 or 32 bits, that's why there's no SQ loss.
Click to expand...

Well, thanks. Now you’ve got my curiosity piqued. I guess I’m going to have to actually look into this to understand what y’all are talking about. And so it begins...
 
jcg1112 said:
Well, thanks. Now you’ve got my curiosity piqued. I guess I’m going to have to actually look into this to understand what y’all are talking about. And so it begins...
Click to expand...

This is probably a somewhat simplified explanation but each music sample is a number that represents the signal level encoded as binary. Say it is a 24-bit digital volume control, 24 bits is naturally more bits than 16, so when the original 16-bit sample (the Xs below) is converted to 24 the least significant bits are simply padded with 0s:

XXXXXXXXXXXXXXXX00000000

Now, you can take all these 16 bits as is and shift them so that they now occupy the lowest 16 bits effectively reducing the signal level 2^8 = 256 times or about 48dB, that's your digital volume control range that doesn't cause any loss of the original 16-bit information, in the digital domain anyway:

00000000XXXXXXXXXXXXXXXX

Now, if you play hi-res with native 24-bit resolution a 24-bit digital volume control will cause loss of some bits on volume less than 100%, but many modern DACs are actually using 32-bit inside and the same idea applies.
 
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