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DAC causing annoying hum

 

Silver Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 453
Registered: Feb-07
Here's the background: I'm using a SuperPro USB DAC (http://www.audiomagus.com/component/page,shop.product_details/flypage,shop.flypa ge_modern/product_id,31/category_id,25/manufacturer_id,0/option,com_virtuemart/I temid,27/)

The DAC is connected to my PC via USB, then to my system via RCA cables. Since my system is in my living room (as is the DAC), and my PC is in my basement, I am running the USB cable through a hole in the floor. Since the USB cable that came with the DAC is too short, I had to use a DAC extension cable.

The problem is that when I switch to the input that my DAC is connected to (in this case CD), I hear a really annoying hum even at low volumes.

At first I thought it was a ground loop caused by the power supply of that DAC, but the hum continues even if the DAC is unplugged. The only thing that will stop the hum is unplugging the USB cable from the PC.

I have tried using a different PC, with the same result. I have similar PC based system elsewhere with no hum. The only difference is that this one uses the USB extension cable.

Could this be the cause?
 

Gold Member
Username: Nuck

Post Number: 9414
Registered: Dec-04
Seems so Dave. What pc source are you using? Does your sound card offer a s/pdif connection?
For runs like this, I use a card with this connection, and it offers long runs with cheap cabling.
The sp/dif will carry digital signals to the dac.
Mine is a CL X/Pro card with external I/O for guitar, mic and a RIAA for vinyl.
 

Silver Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 454
Registered: Feb-07
Hey Nuck,

I don't even have a sound card in this machine. I'm using the USB DAC so I don't need to bother with a soundcard.

As an experiment I'm going to move the PC out to the living room so I don't need to use the USB extension and see if that eliminates the hum.

If that doesn't work I'm going to pull my hair out, then take it from there.
 

Gold Member
Username: Nuck

Post Number: 9416
Registered: Dec-04
Bald is beautiful.
 

Silver Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 456
Registered: Feb-07
speaking personally?
 

Gold Member
Username: Nuck

Post Number: 9417
Registered: Dec-04
Yeah, I nailed Sinead O'Connor.

Oops, skinead O'Connor.
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