Why do I get hiss on an external DAC?

M76

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I bought an external DAC with balanced output exactly to avoid noise from the PC, but now I constantly get hiss or hum or whatever you call it from the speakers and it is affected by what the PC is doing. If the GPU is occupied the hiss gets worse. If the screen displays bright colors the hiss is less pronounced than when the display is dark.

This is an external USB dac, how can the noise propagate through a digital interface from the PC? Or is it possible the noise is collected by the cable going to the speakers? Or through the mains?

What can I do to get rid of it? Would connetcing the speakers to different electrical outlets help?
 

criccio

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USB is ones and zeroes with integrity checks it can't collect noise like an analog connection.

I know, but its still metal on metal so its possible. I mean it has to be that if you're getting feedback based on what the PC is doing.
 

grim4593

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USB is ones and zeroes with integrity checks it can't collect noise like an analog connection.
Although the transmission is digital the power lines can still have power supply noise on them that makes its way into the speaker outputs. If the DAC does not have its analog circuitry properly isolated from the digital circuitry it can definitely end up with hiss.
I've had this happen with noisy GPUs and lower quality speakers. You might be able to fix it with a USB cord with an integrated ferrite bead or buy a clip on ferrite bead.
 

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M76

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Although the transmission is digital the power lines can still have power supply noise on them that makes its way into the speaker outputs. If the DAC does not have its analog circuitry properly isolated from the digital circuitry it can definitely end up with hiss.
I've had this happen with noisy GPUs and lower quality speakers. You might be able to fix it with a USB cord with an integrated ferrite bead or buy a clip on ferrite bead.
I have multiple ferrites tried playing around with them, but no matter where I put them they didn't seem to affect the hiss.

The thing is intermittent too, one day its fine, next day I get the noise. It's not going on right now for example.
 

N4CR

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Ground maybe? Probably not if hiss but worth a try.
Try isolating it on amp end.
 

DoubleTap

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Are you using any kind of analog input to the PC? Either a 3.5mm Mic or a 3.5mm Line in?

I use the 3.5mm Line in to mix the output from my Amazon Echo View - I found that if I just leave the 3.5mm cable disconnected from the Echo (but plugged into the PC) or if I have a dirty power source, then I get induction or power noise going in through that port and it gets inserted to the digital stream.

The previous Echo I had was USB powered and most USB chargers were super noisy. The little Apple one worked great and didn't introduce noise.
 
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travm

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Did you buy a shitty DAC?

Check the power supply (wall wart?) And try a ferrite there too. If it's a shitty amp design or a bad PSU it just is what it is.
Could also be dirty power. Is the amp usb powered? If it is you could try a powered usb hub to get the power supply right out of your PC.
 

thesmokingman

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I'm using a Fiio K5 Pro with usb cable (along with a Micca OriGain amp) and its unfortunately sandwich between a bunch of power cables with no noise/distortion. Maybe its your unit?
 

GotNoRice

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I get minor hiss when using my Maverick Audio TubeMagic D2 on either USB or Coax S/PDIF. It's definitely coming from the computer as it changes when I move my mouse. It's not as bad as the similar hiss I would get when using my X-Fi Titanium by itself inside the computer, but it's still there.

I don't get any hiss whatsoever when I use optical S/PDIF between my X-Fi soundcard and the DAC. I sort of expected that this would be the case, even before I got the DAC, which is why I made sure to get a DAC that had optical input.
 

Nenu

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I have this issue with my AV system + PC and it only happened after I changed from a pre-amp + power amp to a full AVR, playing through the same power amp.
I also have an external DAC that plays into the same power amp "which doesnt have this problem".
I narrowed down the cause but havent fullt sorted it yet but its good enough for me not to care.
With music through my external DAC I dont have the problem at all so I'm not further motivated than what I did below.

I was originally running an AV pre-amp that had an earth connection to the mains.
My new AV amp doesnt use an earth connection and when my computer is connected to it (even when watching TV), I hear the PC processing loudly when it is working hard or if the mouse is moved. The volume level makes no difference from the PC or on my AV amp, the processing noise is the same loudness.
All other equipment has an earth connection (external DAC, PC, power amp). I imagine the situation can differ if any of those are earth less.

The issue is a form of ground loop.
I heard a quick fix is to remove the earth from my PC but I wont take this risk.
I tried chokes on the PCs power, HDMI and USB connections but they didnt help at all.
In the early moments of isolating the cause I found using a 50m extension reel to power the PC from another room removed practically all the noise. It doesnt matter where the extension is plugged though, it still works. So I left it this way, it does the job and the reel is hidden.

This is just an fyi in case its useful as a solution or to help diagnosis.
If I hadnt found this simple fix I would have pursued it further.

ps
Within the last year I changed my PSU from an 8 year old Corsair AX750 to a Seasonic Prime Ultra Titanium 750W.
Using a direct mains connection to the PC (without the extension reel) the processing sound coming from my speakers had reduced a lot but it was still substantial enough to continue using the extension, I thought it worth a try.
So the route through the PSU for electrical noise from the PC can be reduced with a good PSU but isnt a full solution.
Better mains isolation will help however you can achieve it.
 
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Danny Dawg

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Nov 5, 2008
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Some things I have run across in the past:

- Does your external USB DAC need the DAC's own USB driver to function properly?
- Do you have an impedance mismatch between the headphones and the DAC?
- In the WIndows Control Panel, ( I am on Win 7, not 10) do you have the proper settings for the sample rate aligned with what the DAC can handle?
 

XoR_

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I had similar issue with Little Dot MK3 and anything connected to PC
Solution was using socket without ground pin.
I intend to get separation transformer just to be on safe side but always forget to buy it =P
 
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