DACs With and Without Auto-Mute

[wacomme]

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]

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.

 

[wacomme]

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]

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.

 

[wacomme]

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]

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!

 

[wacomme]

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.

 

[MRC01]

Well, the SMSL SU-6 is less expensive than the DO100. I can't tell, but does it have balanced connections?
...

Nope. You can read details in Amir's review here on ASR.

 

[morethinkingcapacityneede]

Old thread, but thought I’d post because I found the same issue with my DO100. When using spdif in (optical or coax), but strangely not USB in; it mutes when doing sweeps with R only. Took me too long and 2 USB-SPDIF bridges to figure out. With REW you can set an option to play dither in silent parts of the sweep which fixes the issue.

From REW website:

“ If Fill silence with dither is selected the generator will replace silent parts of the sweep with 16-bit dither. This option is provided to try and counter aggressive output muting which some DACs exhibit when one of their input channels does not have any signal. There is some penalty in the impulse response noise level, though it is far below the noise floor for acoustic measurements, only potentially having an impact when measuring electronics. Nonetheless the option should only be selected if required to counter device behaviour.”

Really like the DO100 otherwise

 

[MRC01]

From REW website:

“ If Fill silence with dither is selected the generator will replace silent parts of the sweep with 16-bit dither. This option is provided to try and counter aggressive output muting which some DACs exhibit ...

This is helpful but won't always work because some DACs trigger output muting at higher levels, like around -87 dB. That's high enough for the DAC to auto-mute even with 2 bits of dither.