Sunday, July 26, 2015

DAC output level measurements

Since this blog is my notebook, here are the measurements of my various DACs, with 10M DMM loading (sorry didn't bother with different), at about -26dB (whatever level, it was consistent):

Denon DVD-5000:
L: 41.6 mV
R: 41.5 mV

Onkyo RDV-1:
L: 48.8 mV
R: 48.0 mV

Audio GD DAC 19
L: 63.0 mV
R: 63.3 mV

The Onkyo does show the most inter channel difference at 0.14dB, which is just above the usual 0.1dB matching requirement.  The Denon is the most tightly matched at 0.02dB.

I suspect the Denon has comparatively low output because it is saving output range (which may actually peak above 3V) for HDCD boost, but this is just a guess.

This shocked me to calculate, but the Audio GD is 2.2dB (left) and 2.4dB (right) louder than the Onkyo.  I would expect the measurements with actual amplifier loading (22k ohms) to be 0.2dB or less different at most and probably below 0.1dB different.

While ABX testing sets a condition at 0.1dB matching, typical matching isn't that good.  Some preamps with steps won't let you set balance closer than 1dB, though 0.5dB is common on digitally controlled preamps.  Old fashioned potentiometer volume controls might have +/-3dB inter channel mismatching (a 6dB total range)--so you really needed to use the companion balance control.  (I was glad to dump those in my then-main bedroom system in 2005 or so with a Classe CDP-35 preamp with digital volume control in no small part for the sake of being rid of potentiometer balance variation, which I barely remember but when I do it is with great dread.  Even my Aragon 28k preamp had considerable channel variation at the very low position I had to use on it.

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