[av2606]

I have this weird problem with my DAC and I think it may be down to the stock PSU (wallwart) I'm using. Could it be something else?
 
Basically I have my DAC/amp combo (Topping D3) connected via USB to my Windows 7 PC. Occasionally, when the boiler turns on or a mains switch is switched on or off, there is a pop from my sound output (be it headphones or RCA out). Windows 7 makes the disconnected USB sound and then reconnects a few seconds later. I have to restart the browser or audio player to get the sound working again.
 
I don't get any noise or random disconnects, it happens only when a mains switch is switched on or off or when the boiler comes on.
 
It's an annoying problem. Any ideas as to what can be causing this?

 

[NA Blur]

Sounds like the voltage at the wall plug is dropping down below spec when the mains / boiler kicks.  This causes your PC and DAC to possible both drop in voltage.
 
One easy thing to try, if it is a USB DAC, is to go into power management for your USB HUB devices and remove the power management.  This will allow your PC to provide more power to the DAC.  Not sure if that will work, but it can help.

 

[leeperry]

maybe the cable is the problem? might try something with triple shielding or so.

 

[One and a half]

What really happens is this:
 
When the boiler or light switch, switch off, radio frequency is released...somewhere in the 60Khz to 200kHz range. The greater the AC current the switch has to break, the greater the RF energy. That energy's strength can dissipate from the source via the building's cabling to drag down, eventually, however for the first ms or so, the energy has enough strength to reach the DAC.
 
The RF signal is so strong, that you can hear it, plus, it superimposes on the USB signal lines. The DAC/PC translates this to an error, and the PC disconnects the DAC, since the data is error content.To reset, the PC needs to establish the connection with the DAC with real data, not spikes.
 
The victim here is the Topping wall wart, which allows the spike to pass through, which, for what it does, should do a better job and has failed to do so.
 
How to fix
Several methods.
a) Install an inline AC filter to the wall wart, and not just a voltage suppressor, you need the type with chokes and caps.
OR
b) Replace the wall wart with something better of the same or higher rating, but keep the voltage the same. Linear power supply, which would be worth more than the DAC itself.
c) Install item a) and the PC on the same filter.
OR
Install RF suppression devices on the boiler cutout and all the light switches

 

[One and a half]

Sorry duplication

 

[av2606]

  What really happens is this:
 
When the boiler or light switch, switch off, radio frequency is released...somewhere in the 60Khz to 200kHz range. The greater the AC current the switch has to break, the greater the RF energy. That energy's strength can dissipate from the source via the building's cabling to drag down, eventually, however for the first ms or so, the energy has enough strength to reach the DAC.
 
The RF signal is so strong, that you can hear it, plus, it superimposes on the USB signal lines. The DAC/PC translates this to an error, and the PC disconnects the DAC, since the data is error content.To reset, the PC needs to establish the connection with the DAC with real data, not spikes.
 
The victim here is the Topping wall wart, which allows the spike to pass through, which, for what it does, should do a better job and has failed to do so.
 
How to fix
Several methods.
a) Install an inline AC filter to the wall wart, and not just a voltage suppressor, you need the type with chokes and caps.
OR
b) Replace the wall wart with something better of the same or higher rating, but keep the voltage the same. Linear power supply, which would be worth more than the DAC itself.
c) Install item a) and the PC on the same filter.
OR
Install RF suppression devices on the boiler cutout and all the light switches

Thanks, very helpful. I will post my results.