Mysterious buzz on laptop output

[Stuart91]

I was covering a fairly typical dance school festive show last night. They supplied their own laptop to play the tracks. 

When a track was playing, it sounded absolutely fine. But in between times, the headphone output was giving a loud buzz. It was louder than the tracks themselves, so gating wasn't an option. I didn't have time to do any serious troubleshooting so just had to be quick on the mute buttons as they started and stopped. 

I've encountered plenty of noisy laptops over the years, but never one that behaved like this. The noise only seemed to be coming from the headphone jack, there was nothing noticeable out of the internal speakers when the jack was unplugged. And it was gone completely when a track played - even when there was a silence during a track, no buzz was audible whereas it was blatantly obvious in between. 

I'd have liked to have tried a USB adaptor, but didn't have the chance. Wondering if it's an issue with the sound drivers, or something else? Anybody encountered similar problems?

[bruce]

The "disappearing when something playing" is strange.

Did you try running the laptop from battery?

And... displaying my prejudices here - was it a Dell laptop 🙂

 

[DrV]

Perhaps some power saving technique was disconnecting or powering down the headphone amp when not in use. That might make it go high impedance. Would have been interesting to play a completely silent track and see whether that shut it up.

[adamburgess]

5 minutes ago, DrV said:

Perhaps some power saving technique was disconnecting or powering down the headphone amp when not in use. That might make it go high impedance. Would have been interesting to play a completely silent track and see whether that shut it up.

My old 2012 Mac used to do this. No audio for a while would make a tiny pop in headphones then become a tiny bit hissy. Nothing like an annoying buzz, though.

 

[sunray]

My own Dell (Circa 2005) was absolutely fine as is a current Lenovo but this is something I've regularly encountered when presented with a laptop, so much so I automatically use an isolating transformer which usually removes all problems.

By far the worst machines for this I've found have been Sony Vaio, for a while every majorette group seemed to have one. But back in the summer a Macbook pro with flat battery took the crown with a nasty high frequency square wave scream almost as loud as the media until a transformer used.

Edited December 22, 2022 by sunray

[bruce]

From what Stuart's saying, it doesn't sound like the "normal" (ha!) mains hum that you get with unisolated laptops.

Interesting that the noise is not there when playing anything - even playing silence - but returns when not playing.

Wondering if it's a driver (or maybe power plan) setting causing something to change when no CPU usage. Just speculating...

 

[sunray]

2 hours ago, bruce said:

From what Stuart's saying, it doesn't sound like the "normal" (ha!) mains hum that you get with unisolated laptops.

Interesting that the noise is not there when playing anything - even playing silence - but returns when not playing.

Wondering if it's a driver (or maybe power plan) setting causing something to change when no CPU usage. Just speculating...

 

I get your point, however one AmDram group I helped had noise when the sound card was not in use on a very old 286 laptop, I'd have described it as hash rather than buzz, almost sounded like some sort of compression issue slowly bringing up background hiss but isolation put a stop to it.

As I said I automatically insert a transformer when interfacing computers whether they are mains or battery and don't seem to get these problems anymore.

Edited December 23, 2022 by sunray

[Ynot]

I am a HUGE proponent of never using the headphone out for anything of any import. It's not really designed for this, and it's VERY easy to yank a 3.5mm jack out if there's a lot of desk shuffling.

My venue invested in a simple plug 'n' play USB sound card years ago and on any show I work, it's alwas the recommended option if they have to use their own computer.

 

[Fleeting]

I have to agree with  Tony (Ynot) The headphone output is designed for heaphones and not ideal for a audio out. There are many tales of woe on here where people have managed to phantom power there laptop through the socket. With a laptop the repair is expensive, a MAC is very expensive  I use a small Presonus 24c audio interface. sounds good and the headphone out goes up to "11"

Ian..

[dmxlights]

The OP did not say what program they where using to play the tracks.

I did have a small problem like this summer for a few shows but I put it down to the laptop also connected to the projector in which I did have the earth hum on the first night but quickly muting the channel got me out of the problem. I did have a DI box for the rest of the shows but. I did not connect it when setting up for the 2nd show just to see if it was the projector or not. I did have a hum when not playing tracks but like the OP no hum when playing. I did have the Y split for the headphone/mic with me and when I used that it was gone. I know windows media player was been used as it was not my laptop and I did disable the mic in sound properties in windows and all was fine without the Y lead. I think windows was ducting the hum when something was playing but would hum when not playing.

I know a standard 3.5mm jack (TRS) shorts out the mic in new laptops which now have one jack for both so maybe this has something to do with it. I did have to use the DI box because of the projector.

[Stuart91]

14 hours ago, bruce said:

The "disappearing when something playing" is strange.

Did you try running the laptop from battery?

And... displaying my prejudices here - was it a Dell laptop 🙂

 

Didn't have the chance to run off battery - the owner said the battery was dodgy and I figured I'd rather cope with the buzz than have it die mid-show. 

I didn't catch the actual brand but it may well have been a Dell. Displaying my own prejudices, it looked cheap and plasticky and seemed to be running quite slow.

[Stuart91]

14 hours ago, DrV said:

Perhaps some power saving technique was disconnecting or powering down the headphone amp when not in use. That might make it go high impedance. Would have been interesting to play a completely silent track and see whether that shut it up.

This is an interesting idea - thanks. Certainly brief pauses in tracks were fine. The buzz tended to return a few moments after a track finished playing (so I had a split second to get to the mute button on the channel). I'm guessing that was down to silence on the end of the tracks.

One other potential clue is that every time the headphone jack was plugged in, the computer threw up a dialogue asking what we had connected (headphones, speaker, etc.) and we selected headphone each time. I don't think I've seen that much before and wonder if it might be tied into the power saving techniques...

 

Unfortunately we were very short of time (the client was more preoccupied with addressing the leaking roof in the venue, amongst other catastrophes...) so I didn't have much of a chance to do any troubleshooting. My preference would have been to just move all the files over onto my MacBook and run via QLab. 

As it was, they had some tracks coming off an iPhone (via lightning adaptor) and they played just fine, with no noise at all. 

[Stuart91]

1 hour ago, Fleeting said:

I have to agree with  Tony (Ynot) The headphone output is designed for heaphones and not ideal for a audio out. There are many tales of woe on here where people have managed to phantom power there laptop through the socket.

Fair point. We've got a couple of interfaces that we use for anything critical. For this show I was running into an X32 rack, using a pair of Orchid DIs into the XLR inputs so no phantom issues. I did briefly try it into one of the aux inputs which are on jack connectors, and the problem seemed the same. Stuck with the XLRs so it would stay on the same layer as my mics. 

1 hour ago, dmxlights said:

The OP did not say what program they where using to play the tracks.

 I know windows media player was been used as it was not my laptop and I did disable the mic in sound properties in windows and all was fine without the Y lead. I think windows was ducting the hum when something was playing but would hum when not playing.

I know a standard 3.5mm jack (TRS) shorts out the mic in new laptops which now have one jack for both so maybe this has something to do with it. I did have to use the DI box because of the projector.

This might be it. They were using Windows Media Player (actually, just double-clicking on each file on the desktop, I assume it was WMP that opened by default, certainly looked like it). Didn't have the chance to try any other programs, I'll tell them to download something else and see if that helps in future.  

[d_korman]

I use the cheap and cheerful (£22) Berry UCA222 rather than the phone/mic socket. It uses the standard MS drivers so you can plug it into any laptop, also works with mac I believe.

[dmxlights]

3 hours ago, Stuart91 said:

This might be it. They were using Windows Media Player (actually, just double-clicking on each file on the desktop, I assume it was WMP that opened by default, certainly looked like it). Didn't have the chance to try any other programs, I'll tell them to download something else and see if that helps in future.  

I keep winamp on a usb stick for this very reason and there is/was a plugin for it to get it to play one track and then stop so you could build the play list and the use it which is great. I think I may have the plugin for it somewhere