Audio stutters at start of track - with Presonus Studio 24C

[Pruitt]

Hey all,

Just a quick question asking to see if anyone knows of issues with the Presonus Studio 24C - as I'm running into a glitch that I've never run into before - a stutter at the start of tracks, almost like the computer can't get it together, starts to play the track, then stops and restarts. It's happening on various audio files, mp3 and .wav, but not consistently on any of them. The show is an extremely simple one with basic audio tracks and occasional fades - there's no way it should be taxing either of these systems.

I've established that it doesn't happen when running the computer speakers, but it does happen through the Presonus used with two completely different systems, one of which has worked well for years with the 24c. Adding "load" cues doesn't seem to affect it, nor does starting the track and fading into it. Everything points to the Presonus, despite it working well in this same theater for three other shows over the last year and a half (with the older system listed)

System A - New Macbook Air M2 with highest available specs (including a 2TB SSD) running the latest version of Monterey and Qlab 4.7

System B - 2015 13" Macbook Pro w/ top of the line specs and i7 chip running High Sierra and Qlab 4.62. This computer has run countless shows with the Presonus and this has never been an issue in the past. I'm a fan of using the 4 outputs for L/R, subs, and stage monitors with bus power and a small footprint, and I'd like to be able to keep doing that!

I've "fixed" this show by going out of the headphone jack into an audio mixer, but I'm curious if anyone else has had issues with this interface. Like I said, I've used it for several years with great results on the older Intel system. When it started glitching on the newer system, I assumed it was a problem with the new M2 machine, but that doesn't appear to be the case, unless the problem could be that it was built on the newer machine and the issue is somehow carrying over when moved to the older one?

Very puzzling.

Stephen

[Philip Perkins]

We have a 26C (black box) and its predesessor (2/6, blue box) that we’ve used without issue with 4 different laptops, including and M1 type from last year, QLAB 4 all around.

We didn’t change anything we were doing vs other DACs (Focusrite, Peavey etc etc), they just work….  Does everything look good in “Audio MIDI” on that computer?

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[Pruitt]

The Audio Midi app looks fine just eyeballing it - nothing unusual. But again, it's also happened on the older, "stable" system. It did occur to me late last night that I could try going in and increasing the buffer size in preferences. I've never had to do that before with Qlab 4, but given that it's acting like it doesn't have enough resources to keep up, that could have an effect. I'm also going to try working with it with full logging on for a bit, and try to catch a log of what's going on (I didn't before because I kept thinking I knew the problem).

[Sam Kusnetz]

I’ve never used that exact model, but Presonus does not have a terrific track record.

This is just one data point, I’m not saying anything certain!

-sk

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[Pruitt]

Okay, well, an update on this:

The problem continued throughout the weekend run, and nothing I tried fixed it, not even eliminating the Presonus completely and just going out of the headphone jack.

The problem happened on 4 different tracks, but none of them consistently. Two were .wav files, and two were mp3s

It happened with the presonus digital output, but also with the headphone jack into a mixer.

It happened on two different laptops with different hardware (2015 Macbook Pro Intel i7 and 2022 Macbook Air M2) and Operating Systems (High Sierra and Monterey)

It happened on two different versions of Qlab (4.62 and 4.7)

It continued after bumping the audio device buffer size to max (1024) on both the headphone jack and the Presonus.

It continued in Show mode vs Editing mode - my attempt to eliminate underlying apps or programs using resources.

I haven't yet managed to reproduce it when using the internal laptop speakers.

I ran the last show with verbose logging, but haven't had a chance to look at the console yet to see what it said.

The only thing I can think of is that somehow my show was corrupted in the original build? I didn't try re-importing the tracks and starting over, but I may try that this week, just to get some peace of mind about what was going on. This is the first time in more than twelve years of using Qlab that I had issues I couldn't resolve and was on edge about it. It was not a fun experience, but also reminded me what an absolute gift it's been for all these years to be able to trust it completely. I'll update once more if I finally figure out what was going on.

-Stephen

[Chris Ashworth]

Hi Stephen,

Is the sample rate of your test files the same as your output device? 

In some source material, if the rates do not match, the process of converting from one sample rate to another can introduce audible artifacts. This doesn’t happen in all cases but in some it can be quite apparent.

I recommend against running a show with verbose logging, as that is likely to exacerbate problems and would tend to make them worse. Verbose is only something to use when specifically testing for something, rather than during a show.

That said, if you do have console logs you can send them in to us and we can look for signs of buffer dropouts or CPU overloads.

There isn’t really something that could be corrupted in the workspace to cause this, so you don’t need to try rebuilding it.

Best,

C