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DACs With and Without Auto-Mute

wacomme

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What's the purpose of auto-mute in dacs? I ask because my SMSL DO100 certainly has it, and it's a PITA. Granted, it seems to work fine under normal listening conditions, though I have heard other people having issues with silence in certain tracks, but to conduct REW measurements and resulting EQ filters, the auto-mute function rears its ugly head. Here's my story . . .

It's just a huge bother when conducting REW measurements with the right channel; apparently, auto-mute looks at the L channel and if there's no sound it shuts down. Thankfully, turning the dac off and back on for each R channel REW measurement seems to create an accurate and trustworthy frequency response measurement for the R channel. Also, if I use Speaker Cal for the pink noise rather than Full Range, I can push continuous sound out of the R monitor and thus be able to synchronize the loudness of each monitor (adjusting gain on back of monitors). If I switch to Full Range pink noise, I get at most a second or two of sound from the R monitor (L channel and monitor are NOT affected), and I must turn off and back on the dac to get any additional sound from the R channel.

Now, I don't think I have any R channel issues, per se (I've already replaced the DO100 thinking the dac had R channel problems), but the auto-mute seems to serve no useful purpose. Why have it? It also makes me wonder if I should return the DO100 altogether and buy a dac that does NOT have an auto-mute function. What's the opinion on this matter? Is an auto-mute dac a device that should be avoided? If so, what dac is a suitable replacement? I need a dac with volume control and balanced connections.
 

MRC01

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Auto-mute is uncommon but not rare, though it's often undocumented. The ones I've seen trigger at a level just above dithered 16-bit, around -87 to -90 dB. Often it's not instantaneous but has a time delay of a few seconds. In my view it's a "bug" or flaw in a DAC.

I've also seen DACs that shut themselves off or auto-mute when signals are played in just one channel. For example the Topping EX-5 does this if the R channel is loud while the L channel is quiet (after 25 secs at 44.1k or 5 secs at 192k).

Perhaps this is something that @amirm could add to his test protocols: play 24-bit audio with white noise at -120 dB for a full minute and see if it mutes. Do this with (A) both channels quiet, (B) R channel loud (white noise @ -1 dB) and L channel quiet (white noise @ -120 dB) and (C) reverse of B. If the DAC auto-mutes, that's a fail. We'd see a few of the DACs fail this test.

Of course you can run this test yourself when it's new and return if it fails, as I have done.
 
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wacomme

wacomme

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Auto-mute is uncommon but not rare, though it's often undocumented. The ones I've seen trigger at a level just above dithered 16-bit, around -87 to -90 dB. Often it's not instantaneous but has a time delay of a few seconds. In my view it's a "bug" or flaw in a DAC.

I've also seen DACs that shut themselves off or auto-mute when signals are played in just one channel. For example the Topping EX-5 does this if the R channel is loud while the L channel is quiet (after 25 secs at 44.1k or 5 secs at 192k).

Perhaps this is something that @amirm could add to his test protocols: play 24-bit audio with white noise at -120 dB for a full minute and see if it mutes. Do this with (A) both channels quiet, (B) R channel loud (white noise @ -1 dB) and L channel quiet (white noise @ -120 dB) and (C) reverse of B. If the DAC auto-mutes, that's a fail. We'd see a few of the DACs fail this test.

Of course you can run this test yourself when it's new and return if it fails, as I have done.
In my case the DO100 auto-mutes when the L channel is quiet. When conducting R channel REW measurements I see a sudden frequency dropoff at around 5kHz. This can be circumvented by turning off the dac and turning it back on before each R channel measurement, but . . .
 

MRC01

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Try lowering the level of the sweep to -12 dB. With the EX-5, this does not auto-mute. It auto-mutes only when the R channel is loud and the L channel is silent. If the R channel sweep is at -12 dB it doesn't auto-mute even if the L is silent.
Of course, this should not be necessary. It's just for troubleshooting & curiosity.
 
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wacomme

wacomme

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Try lowering the level of the sweep to -12 dB. With the EX-5, this does not auto-mute. It auto-mutes only when the R channel is loud and the L channel is silent. If the R channel sweep is at -12 dB it doesn't auto-mute even if the L is silent.
Of course, this should not be necessary. It's just for troubleshooting & curiosity.
This is good to know.

Are you keeping the EX5 is spite of the auto-mute? It just peeves me that my DO100 auto-mutes, and I'm looking at other dacs for a possible replacement. I may "just get over it", but it irritates me that my dac has this "abnormality".
 

MRC01

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The EX-5 also had another bug in which it did not display the correct sample rate. I reported both bugs to Topping. They never responded, though one of the members here works for Topping and contacted me privately when I posted it. Topping could not fix the bugs so I returned the EX-5. It was for my desktop system, which now has an SMSL SU-6 that does not have either of these bugs. It's a keeper!
 
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wacomme

wacomme

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The EX-5 also had another bug in which it did not display the correct sample rate. I reported both bugs to Topping. They never responded, though one of the members here works for Topping and contacted me privately when I posted it. Topping could not fix the bugs so I returned the EX-5. It was for my desktop system, which now has an SMSL SU-6 that does not have either of these bugs. It's a keeper!
Well, the SMSL SU-6 is less expensive than the DO100. I can't tell, but does it have balanced connections?

I'm also wondering if I should stay away from SMSL altogether. How are their products for reliability? Is Topping better? Schiit? I'd like a dac that will last many years without issue.
 
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