DAC muting function doesn't work as it should issue

[Sandm0n]

Hi All,


I have 2 DACs with the same issue, Orelle DA-180 and Maverick audio Tubemagic D1, when I use the optical or coaxial inputs and switch between tracks in my audio streamer I get a "hiss" noise in my speakers.
While using the Orelle DAC there is this noise then 3 seconds silence and then I can hear the muting relay clicks and then music, in the Maverick audio DAC there is this noise then relay click and music, there is no silence like in the Orelle.
There is no noise when I'm using the USB input in the Maverick audio DAC or using an external USB to toslink/spdif converter.
Unfortunately I don't have the DACs schematics and cannot find one.
Does anyone have an idea what can be the cause for it or what components on the PCB controls the muting relay response speed? it feels like the relay doesn't respond fast enough to the muting signal.


Thanks

 

[Markw4]

Its probably caused by a dropout in the optical or coaxial signals, and the mute circuity in the dac too slow to catch it. Not an uncommon problem with some dacs. Also, it might be made worse by the source device sending the optical or coaxial signals if it doesn't set the output volume to zero before momentarily cutting out.

 

[Sandm0n]

Thanks.
I would like to know which part in the DACs controls the response time of the muting relay?

 

[Markw4]

It may be operated by an MCU chip on the dac board, or it may be operated in some other way. You might have to follow PCB traces to the relays to see where they are operated from and what device is monitoring the need to mute.

 

[Sandm0n]

If it helps, the DIR chip in the Orelle DA-180 is YM3626B and the digital filter chip is YM3434.

 

[Markw4]

The DIR chip part number you gave does not turn up any datasheet in a google search. Either its not a good part number or datasheets must be very rare.

 

[Sandm0n]

Sorry, my mistake, it’s YM3623B

 

[Markw4]

Datasheet attached below. It does have an ERROR pin if there is a parity error. It also may have its clock output signals drop out if there is an input signal dropout. Looking with a scope while changing tracks my tell you if its signals could be useful for muting. How long the signals take to react to input changes, and whether or not the dac is already muting as fast as it can when there is some possible triggering condition are a couple of things you might be able to figure out.

 

[synonymous]

Probably nothing in relation, but, in my system, I use shairport-sync. If I use my linux machine (which I usually do) I get little tiny tiny artifacts when the tracks are changed, while using something like Apple TV I get none. The folks that make pulseaudio for linux apparently have dithering built into the system that takes care of the streaming to networked audio devices, while the Apple TV unit apparently can tell that I have a hardware volume control on my DAC. Volume changes on the linux machine result in both an instant hardware change followed my a dithered volume change, while the Apple machine only adjusts the hardware volume on the DAC (which of course is best). It would seem a simple change in the code for the pulseaudio guys by removing instead of difficulty adding.

Nothing in the ways of muting for you, but maybe the sound system is still open somehow

 

[Sandm0n]

Here you can see the marked resistor that in connected to the Err leg of the YM3623B and to a set of transistors and the relay, it’s definitely the mute “mechanism”, how can I know which part sets the response time of the relay?

Let’s say I can live with the momentarily hiss noise when I switch tracks but the 4 seconds gap is really annoying.

Thanks

 

[Sandm0n]

I don’t know if it’s related but I noticed that a capacitor that is connected to the YM3623B leg 7 (Kmode) has been previously replaced for some reason but I don’t know what was the original capacitor value.

 

[Markw4]

I would suggest to measure what is going on with a scope first. From the time you, say, unplug then replug the SPDIF or TOSLINK input, how long does ti take for the Err signal to be asserted. How long does it stay asserted afterwards? If the signal is late to assert, your problem would appear to be before the relay and transistors.