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What volume level should a DAC be set to when feeding your Pre Amp

G'day All

I have an Accuphase DAC (DC-901) with a digital volume control that feeds my Pre Amp/Accuphase integrated Amp.  The DAC is fed via USB. It reports its volume level in db and altering the volume on the DAC impacts the volume level coming out of my Integrated.  I currently have the DAC set at 0.0db. This DAC level is purely a guess on my part not really understanding the technicalities of it all.  I'd like to understand better the implications of this DAC volume setting on my overall listening experience and whether or not the setting I have in place currently is correct.

Any advice appreciated.

Cheers
plb02
plb02 OP
25 posts
 
Thank you George.

I had "randomly" picked -15db on the DAC (its range is -80db -through 0db.  The only reason being this resulted in my Integrated sitting between 9 and 11 oclock on the volume control for regular listening levels.  I may have blindly determined the correct setting with any rhyme or reason. I have tried 0db on the DAC (full volume) and had no discerning change in sound quality (my ears are not that young). I also wasnt keen un running the volume way up to between 12 and 3 oclock for low level listening when the DAC was set to lower levels. I may be mistaken but figured this was working the Amp harder.

Cheers
georgehifi's avatar
georgehifi
10,312 posts
 
I may be mistaken but figured this was working the Amp harder.
No the same, just letting the same amount of input signal through the volume pot to the power amp section, instead of shunting it to ground when the dac's vc is higher.

Cheers George 
kijanki's avatar
kijanki
4,394 posts
 
0dB FS (full scale) should correspond to 24dBu.  Since 24dBu is a level related to 0.775V (1mW over 600ohm) it will correspond to 12.3Vrms.  When you selected -15dB your DAC would output  24dBu-15dB=9dBu = 2.2Vrms.  I'm not sure what nominal level should be.  I looked at one of the power amps that outputs 125W at 8ohm and has gain of 26dB.  That would imply 1.6Vrms input.  My current power amp Benchmark AHB2 has high gain position of 8.2dBu=2Vrms.  You should be OK.  My previous DAC had jumper selections of 0dB, -10dB and -20dB.  The best position for driving power amp direct was -10dB. 

You might find this useful:
https://www.av-iq.com/avcat/images/documents/pdfs/measdigaudlvls.pdf 
junzhang10
252 posts
 
Line out level
georgehifi's avatar
georgehifi
10,312 posts
 
plb02 OP

It seems like your on a winner, it looks from other posts you have the Accuphase E470 integrated, it has poweramp inputs at 1.5v in for full wattage output on the back so you can forget about the preamp section, for the best most transparent/dynamic sound I would feed your dacs output which has up to 2.5v output direct into these poweramp inputs and just use the dac’s volume control.

Cheers George
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