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DAC output voltage / level and distortion

gags11

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This may be a naive observation or question, but reading reviews of many dacs tested in this site, it strikes me that many of them perform better when their output is set less than the max, or zero gain. Some of them start distorting really bad at 0db gain, like the Mytek Brooklyn.

I would like to understand this a bit better. Mytek, for example, outputs 6 volts from its analog outputs when volume is to zero. It sucks at that level, and improves when turned down. Matrix X-Sabre Pro outputs 4 volts at volume 0. But they mention that there is a built in headroom. Does this mean that DACs also need headroom? Or does Matrix on purpose decrease or limit its 0db to 4 vs 6 volts to preserve some headroom and improve distortion?

My subjective observation with Mytek Brooklyn DAC + is that when my active crossover attenuators are out, and the Mytek is outputting much lower voltages (using analog volume), I hear much cleaner and more dynamic sound compared to when attenuators are in. Say volume set to -2db with attenuators vs -14db without. The caveat here is that the attenuators may be degrading the sound, but the designer of the active crossover, Phil Marchand, is sure that the attenuators actually improve SNR.

Every DAC is different and have different output voltages. It would be interesting and kind of important to test them with a set output voltage in order to compare SINAD. I would love to see how the Mytek DAC+ performs at the same output voltage as the Matrix DACs.

As I mentioned in the beginning, these may be very primitive and naive observations. Would like to hear and learn from you all. Thanks in advance!
 

RayDunzl

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Does this mean that DACs also need headroom?

Spec of my Benchmark DAC2:

0dBfs output, 2Vrms

Analog section clip point : 3.7Vrms

1570596182262.png


3.7V / 2V = 1.85 voltage ratio

1570596385534.png


So, if I read this correctly, the analog section following the DAC has 5.3dB headroom on the unbalanced outputs.

The balanced outs:

1570596649002.png


Looks like 5dBu headroom...

29dBu = 21.83V
24dBu = 12.27V

Ratio = 21.83 / 12.27 = 1.779 = 5.003dB headroom.

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There may be some spoofing in the digital pipeline to take care of digital inter-sample overs, but I don't have a clear explanation of what goes on there. I suspect an attenuation of the digital signal before the data hits the converter.
 
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gags11

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Thanks for the response! It seems that many DACs do have built in headroom to avoid clipping. It’s nice that Benchmark actually lists all that information in within their specs.
 

HammerSandwich

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Benchmark explains "inter-sample overs" here. I don't recall how the Mytek does volume, but reducing the digital signal by >3dB should avoid this issue.
 
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