audio pops in built-in audio

[Brendan Aanes]

Hi All,

I'm having an issue with a show where my speakers connected to the Mac Mini's built-in outputs are very occasionally popping - as in, every 60-80 minutes. Most audio in the show is running off of an M-Audio Fast Trak Ultra, which is not exhibiting these problems. The speakers that are popping are running off a small amp in the tech booth, while all the others are active speakers powered from dedicated sound outlets. I am not using aggregate device, rather just patching them separately.

One oddity - I have never heard the pops when Qlab isn't open. But since they're so intermittent, this may be coincidence.

I also tried running a silent audio cue through the built-in output at all times, in case the built-in audio device was sleeping or such, which did not fix the problem.

So there are a couple variables: is it the built-in output, is it a power spike hitting the amp (seems most likely, but nothing else in the building has issues), or is it some software glitch? Any ideas or similar experiences?

Thanks,

BA

[ra byn (robin)]

On Tue, March 20, 2012 7:25 pm, Brendan Aanes wrote:
> So there are a couple variables: is it the built-in output?

One way to find out is to patch the builtin output into a audio recorder &
let it record for a few hours (long enough to see your issue). Then look
on the wave file for spikes.

> is it a power spike hitting the amp (seems most likely, but nothing else
in > the building
> has issues),

Disconnect QLAB Mac / built in audio from amp / speaker. Listen for X
amount of time. If you hear the noise ever again, its not Qlab or the Mac
of course.

>or is it some software glitch? Any ideas or similar
> experiences?

If you really think it might be an internal issue, you could try to patch
the output of Qlab virtually via Soundflower or Jack into Audacity or some
other app & just record it sitting there for a few hours.

If it's being generated in Qlab (doubtful), you'll see the spike which
will eliminate the possibility of it being the amp / speaker / built in
audio output.

Let us know what you find.

[Joe H]

We have run into this issue with certain configurations, and it was
always solved by using an interface instead of the Mac output, meaning
it was a Mac issue. Particularly happened with laptops, but since our
Minis almost never run without an interface it's hard to say.

[Matthieu Gaillet]

+1 : I never use the built in output : it is really unreliable, prone
to fail, disconnect, and subject to unsolder easily. Better using an
USB or FW audio interface.

[Brendan Aanes]

For those interested, I recorded the mini's built-in output overnight, as well as putting a mic next to the popping speaker with the amp on but disconnected from any input source. Neither registered any pops. Pretty weird. I did notice that the pop seemed to happen less and be softer in volume once wireless was disabled on the host computer, but this could also be a coincidence.

Anyway I convinced the company to get a MOTU interface, which was an easy sell as their M-Audio periodically would spit out white noise upon startup. No pops, and everything sounds better as well.

And agreed that built-in output is never a good choice, but sometimes you don't have the gear you need and 2 more channels appeal. I and other designers have used this system for a number of shows and never had this problem before, hence the surprise.

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[ra byn (robin)]

On Sat, March 24, 2012 4:27 pm, Brendan Aanes wrote:
> And agreed that built-in output is never a good choice, but sometimes you
> don't have the gear you need and 2 more channels appeal. I and other
> designers have used this system for a number of shows and never had this
> problem before, hence the surprise.

I've used the headphone out for more hours that I can remember during
studio rehearsals & I've never heard a single pop.

This isn't an advocation for using headphone outputs for shows but if all
headphone outputs always had issues all the time, we'd all know it. This
isn't the case.

ra byn

[Jeremy Lee]

Me neither- it's actually quite stable.  There was one generation of laptop that had a REALLY bad sounding headphone jack.  The newer ones are pretty good as long as you select 24 bit or higher in Audio MIDI setup.

On Mar 24, 2012, at 8:30 PM, ra byn (robin) wrote:

I've used the headphone out for more hours that I can remember during
studio rehearsals & I've never heard a single pop.

-- 

Jeremy Lee

    Sound Designer, NYC - USA 829

        http://www.jjlee.com

[cedricl]

The headphone out is also an optical digital output. With the proper adapter, you can get direct digital output from it and it's very clean and stable. I switched from using a USB audio interface that was giving me ticks and pops to using the direct digital output whenever I'm running shows off the computer. Haven't had a problem since from an older (2007)) iMac.

[Ed R Casey]

How did you clock the computer from the mixer?  Or did you ( gasp ) clock the mixer from the computer?

[Chris Bakos]

Does the optical output play nice with pro gear? 

[Ed R Casey]

Not in my experience thus my curiosity about the OP's clocking plan.

On 27 Apr 2012, at 12:46 AM, Chris Bakos wrote:

Does the optical output play nice with pro gear? 

[Jeremy Lee]

The only time I've ever used it was from the video designer's computer.  The headphone jack was simply totally crap sound.  I ran the optical out into a MD deck that was lying around, put it in D/A mode, and used the audio from that.  Not ideal but better than massive hum and noise hash from the analog headphone jack!

On Apr 27, 2012, at 10:06 AM, Ed R Casey wrote:

Not in my experience thus my curiosity about the OP's clocking plan.

On 27 Apr 2012, at 12:46 AM, Chris Bakos wrote:

Does the optical output play nice with pro gear? 

-- 

[cedricl]

I go from the optical output to the old midiman C02 optical to spdif converter and then into the spdif in on the Yamaha DM2000. Anything into the digital inputs is automatically clocked to the DM2000 unless you tell it otherwise.