[Solved, 4G interferences] Occasionnal noise in audio: grounding issue?
Hello,
I'm trying to cleanup my audio setup. I assume my PC and DAC are clean. But I've an issue that I suspect to be located inside my amplifier, maybe related to ground wirings.
In the amp, a nice build, I added a speaker protection board, powered by a separate small ACmains/DC12V supply. Initially, that was sometime generating noise in the audio, because I routed the 220V line too close to a PCB input channel. I since moved that 220V line away from the amp PCB, but I have still some noise in my audio, similar to such (like occasionnal capacitive coupling/discharge noise, low level but audible noises).
The noises I get aren't permanent (would be easy to fix). They occur shortly, every hours or so, for half a second, and maybe according to the audio tracks I'm listening to (might be related to audio levels, or dynamics, with the additionnal noise triggered or more or less perceptible; fact is that I perceive more such noises with some tracks, tracks that are clean). And most the time, audio is very correct, with no noise at all.
As a next step, I intend to shield the board and converted I added inside.
I will also rewire ground inside the amp, because it came with:
- ground connected to rear aluminium chassis part, from there, to other parts but via painted metal panels....
- audio ground connected to bottom painted metal panel
Can the ground wirings via painted parts be the cause of occasionnal noises I get? I will rewire them with a common point, bolt and nuts, via paint blanked metal parts.
May groundings/shieldings inside a amp chassis cause such noises or shall I search for other sources for those noises I get?
Shaking my amp PCBs with a wood stick causes no noise. So I assume all components and solder joints are Ok there.
Hello,
I'm trying to cleanup my audio setup. I assume my PC and DAC are clean. But I've an issue that I suspect to be located inside my amplifier, maybe related to ground wirings.
In the amp, a nice build, I added a speaker protection board, powered by a separate small ACmains/DC12V supply. Initially, that was sometime generating noise in the audio, because I routed the 220V line too close to a PCB input channel. I since moved that 220V line away from the amp PCB, but I have still some noise in my audio, similar to such (like occasionnal capacitive coupling/discharge noise, low level but audible noises).
The noises I get aren't permanent (would be easy to fix). They occur shortly, every hours or so, for half a second, and maybe according to the audio tracks I'm listening to (might be related to audio levels, or dynamics, with the additionnal noise triggered or more or less perceptible; fact is that I perceive more such noises with some tracks, tracks that are clean). And most the time, audio is very correct, with no noise at all.
As a next step, I intend to shield the board and converted I added inside.
I will also rewire ground inside the amp, because it came with:
- ground connected to rear aluminium chassis part, from there, to other parts but via painted metal panels....
- audio ground connected to bottom painted metal panel
Can the ground wirings via painted parts be the cause of occasionnal noises I get? I will rewire them with a common point, bolt and nuts, via paint blanked metal parts.
May groundings/shieldings inside a amp chassis cause such noises or shall I search for other sources for those noises I get?
Shaking my amp PCBs with a wood stick causes no noise. So I assume all components and solder joints are Ok there.
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Could be interference coming in over the AC line, or else radiated.
Try having an AM radio on at the same time, you may hear it on that also.
Try having an AM radio on at the same time, you may hear it on that also.
Question then still is how do I fix that?
Somewhere I do have a big L/C mains noise filter. Would this then solve my issue?
But it seems more related to tracks I'm listening to, with the noise poping in at the same position. It is perceptible on quiet tracks or vocals only tracks, looping them, but it is not always poping in.
Somewhere I do have a big L/C mains noise filter. Would this then solve my issue?
But it seems more related to tracks I'm listening to, with the noise poping in at the same position. It is perceptible on quiet tracks or vocals only tracks, looping them, but it is not always poping in.
If the noise is repeatable on particular tracks, then it is in the source material,
or a circuit is being overloaded on peaks.
Otherwise, try different times of day and see if it is better or worse.
Sounds more like external interference though, so try the line filter.
Bad resistors or transistors, or bad solder joints, can also cause erratic noises.
Is this in both channels, or just one?
or a circuit is being overloaded on peaks.
Otherwise, try different times of day and see if it is better or worse.
Sounds more like external interference though, so try the line filter.
Bad resistors or transistors, or bad solder joints, can also cause erratic noises.
Is this in both channels, or just one?
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I found some confusing tracks with noise inside, checking with Audacity.
The one I have issues with seem to be clean (and I can repetively listen them, and for periods, get a clean output). I do not think those tracks are the problem; they are mainly vocals or quiet, so the superposed noise (low level) gets more perceptible.
Its a 2x100W amp I'm using at approx 2x10W, I don't think its any overload issue.
Noise may be more present in one channel, the closest to the board I added. This is why I'll shield that board.
Bad resistors or transistors, or bad solder joints: I think I would have noise with much more tracks, and not only with some, at more or less precise positions of the tracks.
I'll try to shield and route my additionnal board better, rewire the groundings, and if I still get noises, I'll test adding the big mains filter.
I also have to change a RCA cable. He may catch interferences (AM or orthers), when I touch it, I get hiss.
The one I have issues with seem to be clean (and I can repetively listen them, and for periods, get a clean output). I do not think those tracks are the problem; they are mainly vocals or quiet, so the superposed noise (low level) gets more perceptible.
Its a 2x100W amp I'm using at approx 2x10W, I don't think its any overload issue.
Noise may be more present in one channel, the closest to the board I added. This is why I'll shield that board.
Bad resistors or transistors, or bad solder joints: I think I would have noise with much more tracks, and not only with some, at more or less precise positions of the tracks.
I'll try to shield and route my additionnal board better, rewire the groundings, and if I still get noises, I'll test adding the big mains filter.
I also have to change a RCA cable. He may catch interferences (AM or orthers), when I touch it, I get hiss.
would you mind posting the inside photos of the nice amp so members can have more clue to locate the fault.
The quickest way may be to spray parts in the bad channel one at a time
with cooling spray, and see if the noise goes away.
Techni-Pro 758CH1672 Techni-Tool Freezer, Chills -62 Deg F., 10 Oz Aerosol Can | JENSEN Tools + Supply
with cooling spray, and see if the noise goes away.
Techni-Pro 758CH1672 Techni-Tool Freezer, Chills -62 Deg F., 10 Oz Aerosol Can | JENSEN Tools + Supply
That is the inside, currently dirty.
The speaker protection board (with a switching AC/DC supply) is in place using foam only, top of capacitors bank. That is the mechanical part I will correct, using a metal shield plus spacers.
I once pulled that board and its cablings to the outside, and got less noise... so I rerouted its 220V line.
You will see the 220V line for this board now routed close to the transformer, away from the channel on right side. Routing this 220V line closer to right side input channel caused more of such interference noise...
Amp being a Q405 clone. So, most the time, and for hours, it works very well. And some rare times, I'm getting interferences, sort of superposed hiss or hum, for approx half a second. I did also get some such noises with no audio track playing. Or do hear more often superposed noises on quiet vocals tracks.
The speaker protection board (with a switching AC/DC supply) is in place using foam only, top of capacitors bank. That is the mechanical part I will correct, using a metal shield plus spacers.
I once pulled that board and its cablings to the outside, and got less noise... so I rerouted its 220V line.
You will see the 220V line for this board now routed close to the transformer, away from the channel on right side. Routing this 220V line closer to right side input channel caused more of such interference noise...
Amp being a Q405 clone. So, most the time, and for hours, it works very well. And some rare times, I'm getting interferences, sort of superposed hiss or hum, for approx half a second. I did also get some such noises with no audio track playing. Or do hear more often superposed noises on quiet vocals tracks.
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As soon as I read “my PC” I thought, oh yeah…
There are so many tasks going on in there that can effect each other and ultimately the sound.
Make sure you have the latest BIOS and that the rest of your software is updated, also there are some tips and tricks to help with audio over a PC as well if you search.
There are so many tasks going on in there that can effect each other and ultimately the sound.
Make sure you have the latest BIOS and that the rest of your software is updated, also there are some tips and tricks to help with audio over a PC as well if you search.
The PC side is updated, I've already worked on that side. The only noise I'm since getting from LAN/PC is when I transfer big files over the LAN, as I'm streaming the music; this activity causing sound interuptions, not superposed noise.
The occasionnal bad sound I'm getting is similar to that coupling noise I more often got with the 220V line routed very close to the input channel on the right side of that picture. This is why I'm now focusing on the amp side, wirings, groundings and shieldings.
The occasionnal bad sound I'm getting is similar to that coupling noise I more often got with the 220V line routed very close to the input channel on the right side of that picture. This is why I'm now focusing on the amp side, wirings, groundings and shieldings.
what a nice amp, neat and tidy.
let's make sure the noise is come from AC or PC,
on the amp board, disconnect the input wire and connect a resistor to short the input to ground, use a resistor around 3k to 5k.
power it on for 1 hour or longer,
if the noise disappear, the noise is from PC.
if it persist, its from the AC supply.
let's make sure the noise is come from AC or PC,
on the amp board, disconnect the input wire and connect a resistor to short the input to ground, use a resistor around 3k to 5k.
power it on for 1 hour or longer,
if the noise disappear, the noise is from PC.
if it persist, its from the AC supply.
> let's make sure the noise is come from AC or PC,
> on the amp board, disconnect the input wire and connect
> a resistor to short the input to ground, use a resistor around 3k to 5k.
Got it. I'll do that as any next step. Because it won't be easy to unscrew input of the right board, due to the way it is mounted, and because I have following to correct.
First, for cleanup as for safety, I'll rewire the ground circuit, around a point, removing some paint on the bottom metal panel. For safety and to avoid shorts on 220V, I'll also better install that board I added, with a minimal shield, as that AC/DC converter may radiate. So far, I more suspect those areas than the pc or the amp itself.
> on the amp board, disconnect the input wire and connect
> a resistor to short the input to ground, use a resistor around 3k to 5k.
Got it. I'll do that as any next step. Because it won't be easy to unscrew input of the right board, due to the way it is mounted, and because I have following to correct.
First, for cleanup as for safety, I'll rewire the ground circuit, around a point, removing some paint on the bottom metal panel. For safety and to avoid shorts on 220V, I'll also better install that board I added, with a minimal shield, as that AC/DC converter may radiate. So far, I more suspect those areas than the pc or the amp itself.
There might be transients in the tracks causing the amp input to start clipping.
Do the earthing properly.
Cheap RCA cables may be two wire though they look co axial, sometimes the shield is open.
Put a MOV on the overall setup board, at the wall from where all the power is drawn, I use one permanently connected line to neutral.
And before that see if same track causes this issue at different types of the day.
SMPS noise inside the amp...can you take the supply from the main unit, removing the SMPS for the protection?
And see the PC supply is clean with good capacitors, check the earthing of that too.
And remove the foam, the heat from the supply needs to be dissipated.
Do the earthing properly.
Cheap RCA cables may be two wire though they look co axial, sometimes the shield is open.
Put a MOV on the overall setup board, at the wall from where all the power is drawn, I use one permanently connected line to neutral.
And before that see if same track causes this issue at different types of the day.
SMPS noise inside the amp...can you take the supply from the main unit, removing the SMPS for the protection?
And see the PC supply is clean with good capacitors, check the earthing of that too.
And remove the foam, the heat from the supply needs to be dissipated.
PC side is generally dirty (PSU noises, graphic card noise, etc). For that purpose, I've a low noise 5V PSU for the DAC. I added also a EMI/VBUS filter between the PC and the DAC. Plus tried with the DAC on a 5V power pack, then via bluetooth (no more PC supply or USB/EMI noises or ground loops issues in that case). I still got those occasionnal superposed low level noises.
So I'm now focusing on the amp side, with my dirty mods (with an SMPS), the groundings, and my currently poor RCA cables. Noise occuring or being perceptible so approx 4-5 times a day. It may be present more often, but unperceptible with pop or rock.
The SMPS (plus noise coming in via mains our due to poor groundings) is a good suspect. As I wrote, since I rerouted the 220V power line of this SMPS, it occurs less often, this is why I'll shield it.
I'll consider all your inputs, and will let you know the outcomes in some days.
So I'm now focusing on the amp side, with my dirty mods (with an SMPS), the groundings, and my currently poor RCA cables. Noise occuring or being perceptible so approx 4-5 times a day. It may be present more often, but unperceptible with pop or rock.
The SMPS (plus noise coming in via mains our due to poor groundings) is a good suspect. As I wrote, since I rerouted the 220V power line of this SMPS, it occurs less often, this is why I'll shield it.
I'll consider all your inputs, and will let you know the outcomes in some days.
I beleive that is fixed now.
Since yesterday, I still get some noises, but they seem to be much more common (like pops when my fridge motor starts, or when I connect my solder iron to mains), and that is probably solvable using a mains filter.
I tested the amp with handy 100k resistors on the RCA inputs, remained silent, as I expected. I did that test for some minutes only, I was pretty confident in that part.
I pulled again away the SMPS: no change, had still those weird noises. SMPS is since back again inside the amp chassis.
Issue was due to currents sometime flowing via the RCA cables, and maybe currents and additionnal noises triggered by some of my precise tracks (the dynamics). Was sort of discrete capacitive discharge or inductive coupling in the RCA cables, more or less audible, according to the audio track levels. I had finally noticed such noises poped also in occasionnaly with the DAC not playing any track, those probably due to mains noises.
I hope my fridge pops and some others, but similar, will now be the last problem with this setup.
Since yesterday, I still get some noises, but they seem to be much more common (like pops when my fridge motor starts, or when I connect my solder iron to mains), and that is probably solvable using a mains filter.
I tested the amp with handy 100k resistors on the RCA inputs, remained silent, as I expected. I did that test for some minutes only, I was pretty confident in that part.
I pulled again away the SMPS: no change, had still those weird noises. SMPS is since back again inside the amp chassis.
Issue was due to currents sometime flowing via the RCA cables, and maybe currents and additionnal noises triggered by some of my precise tracks (the dynamics). Was sort of discrete capacitive discharge or inductive coupling in the RCA cables, more or less audible, according to the audio track levels. I had finally noticed such noises poped also in occasionnaly with the DAC not playing any track, those probably due to mains noises.
I hope my fridge pops and some others, but similar, will now be the last problem with this setup.
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thank you b4nt
you're so kind to let us know the process,
I learn something here and I'll follow.
you're so kind to let us know the process,
I learn something here and I'll follow.
Maybe it comes via Y2 caps of either one of your signal sources or (more likely) from you SMPS. If the SMPS has no PE connection, it has to be connected to one of the mains lines. Depending on how the mains plug is inserted, it connects to N or L. In the latter case 50Hz could be coupled to your ground via the Y2 (necessary for EMC compliance) capacitor.
The SMPS is out of cause. Since I have routed / moved away his 220V line from the input channel neighbour, I got not more noise from inside the amp.
The SMPS isn't floating. Its output minus is connected to amplifier 0V which is earthed, there, any leakage current goes...
I sure get a minimal amout of noise from such a configuration. But I hear so only hiss with the amp+SMPS alone, and my ear very close to a speaker.
I didn't check what the voltages exactly are, the amp boards are powered by +/-30 to +/-50V. Most of the speaker protection boards are given for 24-32V max only. So I picked this autonomous SMPS powered board.
The SMPS isn't floating. Its output minus is connected to amplifier 0V which is earthed, there, any leakage current goes...
I sure get a minimal amout of noise from such a configuration. But I hear so only hiss with the amp+SMPS alone, and my ear very close to a speaker.
I didn't check what the voltages exactly are, the amp boards are powered by +/-30 to +/-50V. Most of the speaker protection boards are given for 24-32V max only. So I picked this autonomous SMPS powered board.
Who cares about L and N? Just checked, that little SMPS has two inputs: AC and AC.
I corrected earthing inside the amp, then added some wires outside the boxes (the red and white ones), they killed a lot of noises.
First I got a loud buzzing system, then heavy hum, finally silence 🙂
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