Hi, I have been using this site for a number of years but this is my first time posting. I couldn't find any similar threads so starting a new one. Hopefully this isn't a double up of an existing thread.
I have recently set up a pair of speakers to go with my PC (old monitor audio bookshelf speakers with a homebuilt gainclone amp). However most of the time there is a very annoying "buzzing" sound when using the PC as my source. This does not happen when using an ipod/phone as the source.
The buzzing noise is always there irrelevant of the volume level on the PC but is gone when I turn the amp volume to 0. I assumed this was from the (low quality?) onboard PC sound card, so I tried using a dragonfly black USB DAC. Unfortunately the buzzing noise is still there with little change! Moving the USB DAC to the front panel USB posts seems to reduce the buzzing volume slightly but it is still there. The frequency of the buzz will change based on the PC usage and seems to be tied to the FPS when in a game. I imagine this is electrical interference from the graphics card?
My question is has anyone else experience this problem and managed to fix it? I have been searching for solutions online and some have suggested a separate 5v power supply for a DAC. Others have suggested replacing the PC poser supply (mine is supposed to be a high quality Corsair unit already). I would love to be able to listen to music while using the PC.
I am in the process of modifying a USB cable to supply a separate 5V signal to the DAC. Will update if this improves the situation.
I have recently set up a pair of speakers to go with my PC (old monitor audio bookshelf speakers with a homebuilt gainclone amp). However most of the time there is a very annoying "buzzing" sound when using the PC as my source. This does not happen when using an ipod/phone as the source.
The buzzing noise is always there irrelevant of the volume level on the PC but is gone when I turn the amp volume to 0. I assumed this was from the (low quality?) onboard PC sound card, so I tried using a dragonfly black USB DAC. Unfortunately the buzzing noise is still there with little change! Moving the USB DAC to the front panel USB posts seems to reduce the buzzing volume slightly but it is still there. The frequency of the buzz will change based on the PC usage and seems to be tied to the FPS when in a game. I imagine this is electrical interference from the graphics card?
My question is has anyone else experience this problem and managed to fix it? I have been searching for solutions online and some have suggested a separate 5v power supply for a DAC. Others have suggested replacing the PC poser supply (mine is supposed to be a high quality Corsair unit already). I would love to be able to listen to music while using the PC.
I am in the process of modifying a USB cable to supply a separate 5V signal to the DAC. Will update if this improves the situation.
With supplying clean 5V you might need to provide initial USB 5V bus for handshake. ADUM USB isolation might help on the USB? Cheap to try anyway.
Oherwise do the PC and DAC have optical TOSLINK?
Oherwise do the PC and DAC have optical TOSLINK?
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Thanks Kazap
I will try the 5v supply and see how that goes, my PC has two USB ports designed to run a USB device with external power so hopefully handshake isn't an issue. The USB isolator is cheep so will buy and see how that goes too.
Unfortunately the DAC only has a USB connection. I need to check but i believe the PC has an optical connection so maybe a new DAC will be a last resort.
I will try the 5v supply and see how that goes, my PC has two USB ports designed to run a USB device with external power so hopefully handshake isn't an issue. The USB isolator is cheep so will buy and see how that goes too.
Unfortunately the DAC only has a USB connection. I need to check but i believe the PC has an optical connection so maybe a new DAC will be a last resort.
The noise of your PC working is not a noisy soundcard/powersupply to your USB DAC, but a ground loop. Does your gainclone PSU have protection earth wire? Very likely.
Powering your USB DAC from independent PSU will not help since the ground wire is still there and the ground loop is still closed, producing noisy differential voltage ground-live in the single-ended dac -> amp line.
I solved the same problem (amp powered from the PC) by using a balanced-input amp and fake single-ended -> balanced connection Adding an Amp into Thin-Client PC
Either try to convert your amp to balanced input, or try to change its construction to class II (without PE - but safely, not just cutting the wire :- ) ), or get a small digital amp and power it with a class II power adapter.
In most cases I am surprised how an internal soundcard of newer PCs (Intel HDA codec) performs when the ground loop is taken care of. If the loop is closed, it is almost always causing problems in PCs since the noise between soundcard 0V and PE wire of the PC is huge due to giant currents running through the motherboard.
Powering your USB DAC from independent PSU will not help since the ground wire is still there and the ground loop is still closed, producing noisy differential voltage ground-live in the single-ended dac -> amp line.
I solved the same problem (amp powered from the PC) by using a balanced-input amp and fake single-ended -> balanced connection Adding an Amp into Thin-Client PC
Either try to convert your amp to balanced input, or try to change its construction to class II (without PE - but safely, not just cutting the wire :- ) ), or get a small digital amp and power it with a class II power adapter.
In most cases I am surprised how an internal soundcard of newer PCs (Intel HDA codec) performs when the ground loop is taken care of. If the loop is closed, it is almost always causing problems in PCs since the noise between soundcard 0V and PE wire of the PC is huge due to giant currents running through the motherboard.
Connect requests (D+ or D- pull-ups) must occur only if VBUS is present, by USB 2.0 specifications Sec.7.2.1. So it is a spec violation just to "have" the pull-ups, the pull-up must be conditional with VBUS.
The ADUM alone may solve your noise without needing the clean 5V supply.
If your doing clean 5V anyway Id suggest making your USB cable for injecting clean 5V as a Y cable with simple pull apart connectors on the USB host VBUS 5v and ground lines. USB receivers like in your DAC may need to connect with the host bus to lock but once connected can be happy to run off external 5v with the host bus pulled.
I seem to remember the ADUM passes little current so depending on the DACs USB receiver powering it might be useful to inject clean 5V after the ADUM isolator and break the VBUS before the ADUM
Ill be very interested to find out what works for you. I reckon your sort it after trying a few combinations.
Phofman and Kazap, Thanks for the responses.
The amp with the nose issue is my second home made gainclone. I opened it up on the weekend to review how it was grounded. As suspected it is grounded through the 3rd power pin which has created a ground loop.
I swapped the amp over with my first home built gainclone with isn't grounded at all, and sure enough the noise is completely gone! Removing the DAC and using the onboard sound card is also clean. The motherboard is new and has a good quality onboard sound card (according to the manufacturer) so still sound great without the DAC. I am quite surprised how much noise was being introduced even with a high end PC power supply and motherboard.
As a solution to the noisy amp, I may keep the metal case ground and disconnect the ground connections from the circuits. Does this have any safety implications? Alternatively I could ground the amp through PC case?
I will also try the clean 5v power supply when I have some free time on the weekend (out of curiosity) and report the findings back.
Thanks for your help!
The amp with the nose issue is my second home made gainclone. I opened it up on the weekend to review how it was grounded. As suspected it is grounded through the 3rd power pin which has created a ground loop.
I swapped the amp over with my first home built gainclone with isn't grounded at all, and sure enough the noise is completely gone! Removing the DAC and using the onboard sound card is also clean. The motherboard is new and has a good quality onboard sound card (according to the manufacturer) so still sound great without the DAC. I am quite surprised how much noise was being introduced even with a high end PC power supply and motherboard.
As a solution to the noisy amp, I may keep the metal case ground and disconnect the ground connections from the circuits. Does this have any safety implications? Alternatively I could ground the amp through PC case?
I will also try the clean 5v power supply when I have some free time on the weekend (out of curiosity) and report the findings back.
Thanks for your help!
The ground loop is not really about noisy supplies/low end MB, but about large currents running through ground traces of the motherboard, creating thus the voltage difference. It is not a fault of the MB, it just works that way. I do not think any other PSU would help, if the ground loop is closed. You checked the actual soundcard output is clean and good.
Grounding the case and removing ground connection from 0V - it depends on your construction and isolation parameters of your transformer. Sure it is the easiest solution, but I am not sure if safe too.
I do not think grounding through PC case would help - the noisy voltage difference is between 0V of the soundcard and the PC PE wire = PC case = your amp PE wire = your amp case. The noisy currents through ground signal line would not be eliminated IMO.
Grounding the case and removing ground connection from 0V - it depends on your construction and isolation parameters of your transformer. Sure it is the easiest solution, but I am not sure if safe too.
I do not think grounding through PC case would help - the noisy voltage difference is between 0V of the soundcard and the PC PE wire = PC case = your amp PE wire = your amp case. The noisy currents through ground signal line would not be eliminated IMO.
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