JRiver 64-bit internal volume control

[lmf22]

From what I understand, JRiver's internal volume control (set to "Internal," not the other options) are processed at 64-bit.  And for every 6db reduction, I would lose 1-bit of resolution.  
 
Does that mean I can safely down the volume by maybe -24db without losing any of the resolution in my music (even with 24-bit music)?  Also, it is better to attenuate by 6db intervals (-6db, -12db, -18db, -24db, etc.)? 
 
I ask because at full volume (100%, or disable volume control) in JRiver, the signal is too loud, and I do not get much range on the volume knob on my integrated amp.  It is a problem because I usually play music at a low volume (around 70-75db).  

 

[stv014]

Quote:

Originally Posted by lmf22 /img/forum/go_quote.gif
 
Does that mean I can safely down the volume by maybe -24db without losing any of the resolution in my music (even with 24-bit music)?

 
Not necessarily, because the 64-bit signal still has to be quantized to whatever your DAC supports (usually 24 bits), and then noise from the DAC and any other components before the final analog volume control further reduces the effective "resolution". So, if you have a DAC with a dynamic range of 100 dB, then 40 dB of attenuation will leave you with only about 10 effective number of bits, regardless of whether the software uses 32, 64, or even 80-bit internal processing.
 
The good news is that the ENOB does not actually have to be that high for good sound quality. You can test that with these files, which show how a 24-bit original sample is degraded by quantizing it (with dither) to various number of bits, from 16 down to 8. Under normal listening conditions, people cannot tell 16-bit apart from 24-bit. Therefore, if you have -110 dB noise from the DAC and other analog components, then, with 24-bit output format, an attenuation of 10 dB is safe, even when listening at relatively high volume. Even more attenuation is still OK at normal volume. For example, with 90 dB peak SPL and 20 dB attenuation from a 110 dB dynamic range, the noise floor will have an A-weighted SPL of 0 dB and very likely not be audible at all, despite the "resolution" being only 15 bits.
 
Quote:

Originally Posted by lmf22 /img/forum/go_quote.gif
 
Also, it is better to attenuate by 6db intervals (-6db, -12db, -18db, -24db, etc.)? 

 
It makes no real difference other than with undithered low resolution formats. With dithering and/or 24-bit output, -6 dB sounds no better or worse than -5.99 dB or -6.01 dB. Also, for exact bit shifting, the gain/attenuation would actually need to be a multiple of 6.0205999132796239 dB, rather than 6 dB.

 

[lmf22]

Thanks for the detailed reply.  So technically, with any digital volume adjustment, I am not getting the full dynamic range and resolution of my DAC.  But practically, I can have -20db (for normal volume listening) and -10db (for high volume listing) and probably not be able to tell the difference.  Seems like it is probably safer to do -10db.
 
I know that my DAC (Bel Canto DAC2.5) has a dynamic range of 122db, but I do not know about the analog volume control's "resolution."  So if I can live with the small range of control on my volume knob, maybe I should just stay with no digital volume adjustment in JRiver? 

 

[stv014]

If you have limited useful volume control range and/or channel imbalance at low volume, then it makes sense to reduce the digital volume and ignore the very likely inaudible increase in the noise floor. You can test how much the analog volume can be increased before any hiss or other noise becomes audible, and if you keep the digital volume high enough that the analog volume is always safely below the lowest "noisy" level, then it should be OK.

 

[lmf22]

Quote:

If you have limited useful volume control range and/or channel imbalance at low volume, then it makes sense to reduce the digital volume and ignore the very likely inaudible increase in the noise floor. You can test how much the analog volume can be increased before any hiss or other noise becomes audible, and if you keep the digital volume high enough that the analog volume is always safely below the lowest "noisy" level, then it should be OK.

 
stv014, I am assuming you are talking about testing the analog volume by turning up the volume knob without any music playing, and see when there is audible noise?  I do not get any noise until almost the highest position on the volume knob.  I have the Octave V70SE integrated amp, and was told that it has a pretty good preamp section and volume control.  
 
My Bel Canto DAC2.5 allows digital volume control.  Should I use the DAC's digital volume instead of JRiver?  I am thinking the changes should be done a far down the audio path as possible.  Does that make sense?