Intermittent buzzing on Topping L30/E30 setup

[Lime1028]

Basically I get this random buzzing, it's 5-7 short 1-3 second buzzes of sound, at a sort of mid pitch (the pitch is the same all the time), and then it stops. It happens randomly, some times it's every 15 minutes, other times it could be an hour between instances. I tried a couple pairs of headphones and IEMs to make sure it wasn't an issue there, happens across all of them, however I did notice something. The volume of it doesn't seem it be depended on the volume set on the amp. On IEMs which are run at a much lower gain the sound is at a noticeably higher volume then on a harder to run set of headphones where it may only be a very small sound in the background. This makes me think it's something wrong with the amp as anything caught in the DAC's output should be amplified by the amp, and therefore very with amp volume, right?

I'm at a loss for what could be causing this. Tons of things can cause constant buzzes but I've never heard of anything like this.

Any and all help is appreciated.

 

[amirm]

Sounds like noise bleeding from your PC into that stack. Do you have the option of using Toslink as the input to them?

 

[Lime1028]

Sounds like noise bleeding from your PC into that stack. Do you have the option of using Toslink as the input to them?

Thanks for the quick reply. I have a port labeled SPIF that looks to be some form of optical, but I must confess I've never connected anything by optical before so I'm not certain of the standards and connectors. From what I'm reading it looks like it's probably a Toslink socket, I guess I'll have to pick up a cable and give that a go.

Can noise bleed really cause an intermittent but consistent pitch sound like this? I would have thought it would be more of a constant hum.

 

[JohnYang1997]

Try unplugging USB cable to verify if it's coming from the PC. Other USB devices connected to the same PC may have polluted the VBUS and the ground.

My other guess is that it's the interference from cellphone, wifi router or something in that nature.

 

[solderdude]

I used to be plagued by these 'tones' (30 years ago)
Especially in the evening.
Later I found out these are PLC tones. (Power Line Communication)
Nowadays a lot of this is > 20kHz and won't bother anyone
Low frequencies are still used for switching on/off street lighting and to set older mechanical electricity meters to day/night positions for instance.
These consists of tones between 250Hz and 400Hz in certain repetitive short 'bursts'.

It could be they are making their way into your audio via ground loop or other way.

Treat this like ground loops (USB isolation)

 

[Lime1028]

Try unplugging USB cable to verify if it's coming from the PC. Other USB devices connected to the same PC may have polluted the VBUS and the ground.

My other guess is that it's the interference from cellphone, wifi router or something in that nature.

Thanks for the reply. Seeing as it happens at times hours apart, I don't have the time right now to sit around for hours listening for noise. I did however order an optical cable, so when that arrives I'll report back if that fixes things, as that should fix any issues on the data transmission side. For power...

I used to be plagued by these 'tones' (30 years ago)
Especially in the evening.
Later I found out these are PLC tones. (Power Line Communication)...

It could be they are making their way into your audio via ground loop or other way.

Treat this like ground loops (USB isolation)

I have a feeling this may be the actual cause as I've heard that there are some things using PLC in my building. This may also explain why there are occasionally big gaps between instances, like right now at 3am, where I haven't heard anything for at least 2 hours. Although, would any such tones make there way through a PC power supply and actually effect the DAC? I would assume not, so it would probably be introduced through the amp right? I may be wrong though, seeing the people in this thread I'm certainly outclassed in terms of experience and expertise.

I'll try to do what I can to isolate the power going into both the amp and dac, I know of a small power conditioning UPS that I can borrow for a bit to test with, and hopefully I can find some time to see what happens if the USB is just unplugged from the PC.

I'll give it all a go in the morning and report back my findings.

 

[solderdude]

The tones are not between L and N but between L/N and ground.
A typical groundloop will be able to do this.
The fibre optic cable will break the loop and the tones will most likely be gone.

 

[Lime1028]

Update: I tried to test some stuff on Sunday, however the sound refused to show up. It was back on Monday though. Tested some stuff and when I unplugged the USB carrying data to the DAC it cut out the buzz (well also all sound to but that's besides the point as the buzz was happening with or without audio playing). Optical cable came in today and I swapped out the USB for it, haven't noticed anything since.

Thanks for the help gentlemen!

 

[Lime1028]

Unfortunately the sound has returned. It seems running over fiber didn't solve the problem. I noticed it again a few days ago but I've been doing some testing to narrow it down since then.

Firstly all the following was performed with 2 different sets of headphones and a pair of IEMs to ensure that it wasn't dependent on the end device.

1. Tried coax, USB, TOSLINK, all of them produced the sound.
2. Tried with no input plugged in and ran through each of the possible inputs selected. All produced the sound.
3. Turned of the E30 and unplugged it's power. Still heard the sound.
4. Unplugged the E30 from the L30, so there was only the power cable and headphones connected to it. The sound was quieter but still present.

All of these were done with the volume nob set to where it was when I was just normal listening to music on each individual set of headphones. This also meant that I was on 0db gain for the headphones and -9db for the IEMs.

So in the end it seems likely that it's either something with the L30, the included power brick, or the sound is coming over from the power. Also not certain why it would get quieter with the input cables unplugged. When I had the DAC connected the sound was very audible, with it disconnected it was more distant. However this not some continuous tone, it sort pulsates in a pattern for about 10-15 seconds, so it was recognizable even at the lower volume.

At this point I'm stumped, do I need to get some form of power conditioning going or is my amp faulty?

 

[D700]

If you haven't resolved it, a cheap suggestion: try a Tripp Lite Ultrablock. If you want something nicer, Brickwall surge protector. I use a Brickwall myself for my home theater, it solved a noise problem I had long time ago in an apartment.

 

[Propheticus]

The sound you describe sounds exactly like what I heard back when I still used powerline adapters for my network. A nice surge/emf protection extension reduced it a bit, but not entirely.
In my case it started out pretty audible and not faint. So if your sound is faint, a surge protector with emf filter might be enough.
My solution was getting rid of the unreliable powerline network, but in a shared building it's of course not really an option to have plc devices removed.

 

[solderdude]

Unfortunately the sound has returned. It seems running over fiber didn't solve the problem. I noticed it again a few days ago but I've been doing some testing to narrow it down since then.

Firstly all the following was performed with 2 different sets of headphones and a pair of IEMs to ensure that it wasn't dependent on the end device.

1. Tried coax, USB, TOSLINK, all of them produced the sound.
2. Tried with no input plugged in and ran through each of the possible inputs selected. All produced the sound.
3. Turned of the E30 and unplugged it's power. Still heard the sound.
4. Unplugged the E30 from the L30, so there was only the power cable and headphones connected to it. The sound was quieter but still present.

All of these were done with the volume nob set to where it was when I was just normal listening to music on each individual set of headphones. This also meant that I was on 0db gain for the headphones and -9db for the IEMs.

So in the end it seems likely that it's either something with the L30, the included power brick, or the sound is coming over from the power. Also not certain why it would get quieter with the input cables unplugged. When I had the DAC connected the sound was very audible, with it disconnected it was more distant. However this not some continuous tone, it sort pulsates in a pattern for about 10-15 seconds, so it was recognizable even at the lower volume.

At this point I'm stumped, do I need to get some form of power conditioning going or is my amp faulty?

How are you feeding the E30 ?

 

[Lime1028]

I have seemingly found the source of the problem. It appears to be my TV hub/thing/I don't know what to call it. Basically all of the boxes at each TV in the house communicates wirelessly with a hub thing that is run off a switch near my computer. I don't have choice about running the TVs this way, it's how both local service providers run their equipment. I got stumped and then came back here and re-read the comments. With Mr. Yang's post, wifi and cellphones occurred to me and I had tested them but then it hit me that the TV thing was wireless too. I stuck it on a longer ethernet cable and placed it further away and I haven't noticed anything since.

For those running into similar problems in the future I would recommend taking your phone, laptop, and any other wireless of cellular equipment out of the room as a first step, since it should be relatively simple to test.

Thanks for all the help.

 

[Propheticus]

So nice that people in this forum actually take the effort to report back how their issue was solved so it could help others.

 

[Taschenrechner]

Having the same problem with my L30 ii.

Picking up radio from my phone, mouse, etc. This sucks.

 

[Dunring]

Having the same problem with my L30 ii.

Picking up radio from my phone, mouse, etc. This sucks.

If it's WIFI that's causing it and you have a 2.4/5ghz network, sometimes just switching your phone to 5ghz will do it. The mouse is likely at 2.4ghz also, but a 5ghz mouse or keyboard isn't expensive. If you start a song, and then turn off wifi on the phone and turn the mouse off for a second, it'll at least narrow it down. Faraday cloth works, but it's conductive so there's that issue.

 

[solderdude]

Having the same problem with my L30 ii.

Picking up radio from my phone, mouse, etc. This sucks.

When you do not connect anything but the headphone to the L30II do you hear it as well ?
Might not be the amp but the combination of gear.

 

[Taschenrechner]

When you do not connect anything but the headphone to the L30II do you hear it as well ?
Might not be the amp but the combination of gear.

yes any combination was tried. The phone always causes interference with this amp. I tried it with a new unit i bought and returned just to test if it is a sample issue. Same problem with the test unit.

It be interesting if anybody could test this with their L30 ii sample. Do a call to a disconnected phone number. Put the phone ear the amp while it is calling.

Do you hear any noise?

 

[Taschenrechner]

If it's WIFI that's causing it and you have a 2.4/5ghz network, sometimes just switching your phone to 5ghz will do it. The mouse is likely at 2.4ghz also, but a 5ghz mouse or keyboard isn't expensive. If you start a song, and then turn off wifi on the phone and turn the mouse off for a second, it'll at least narrow it down. Faraday cloth works, but it's conductive so there's that issue.

Wi-Fi is already on 5ghz. You think 2.4ghz might work? The noise comes from some mobile network activity i think. Like the amp picks up phone calls like it's designed to do that.

 

[solderdude]

Possibly some ferrites or a small inductor close to the headphone connector could have prevented this.
Looks like RF can make it into the feedback loop.
I would expect this would have been spotted in standard EMC testing.
How close does the RF source have to be for this to occur ?