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Digital hash rears its ugly head--why?
Old 1 week ago
  #1
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🎧 15 years
Digital hash rears its ugly head--why?

Something happened to me today that hasn't happened in at least 20 years: I out-and-out blew a recording gig.

It was a high school jazz band recording for an upcoming contest. I've been recording this group for more than a decade, with excellent results. As usual, I was using their digital board, an Allen & Heath QU-32 with a USB-2 out, recording into a Macbook Pro (early 2020, last gen Intel) running Digital Performer 11.02. I've used this basic combination to record this group many times. The MBP and the DP version are new since the last time, but I've used both in other contexts without trouble, so I wasn't expecting any. The incoming channels on the board sounded fine. The tracks in DP looked fine. I thought everything was fine, because it always is.

Aaaand....when I played the tracks back, they were oozing severe digital hash. I've had to tell the band director the recordings are unusable. Given the kids' busy schedules and the contest timelines, this probably means they will not have a contest entry this year--their work is wasted, and it's my fault. I'm in 'keep me away from sharp objects' mode right now.

Anyone have any idea what might be the culprit here? Bad USB cable? It's a relatively new one that I've used successfully before (although it was plugged into a USB-C-to-A adapter; could that be the issue? I thought USB version adapters were pretty trivial tech). Something squirrelly in the interaction between the board and my OS/DP version?

This kind of stuff has worked seamlessly for me for so long, I feel blindsided. Like I've time-traveled back to 2002.
Old 1 week ago
  #2
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🎧 15 years
Clock issue? Was anything clocking the console? Was anything digital plugged into it? Sample rate mismatch? Bummer...hate hearing this kind of tale...
Old 1 week ago | Show parent
  #3
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🎧 15 years
Quote:
Originally Posted by philper ➡️
Clock issue? Was anything clocking the console? Was anything digital plugged into it? Sample rate mismatch? Bummer...hate hearing this kind of tale...
Thanks. The only thing digital plugged into the console was the USB cable connecting it to my computer. It should have been running on internal clock as normal. Sample rate was 48k on both machines.

Old 1 week ago
  #4
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🎧 10 years
Very odd, since you were obviously monitoring the input on cans as the recording took place ?

Too late now, but could you have recorded onto a suitably fast USB thumb drive or external SSD at the same time as the stream out to your Macbook ?

Is it possible the Macbook has its buffers set incorrectly for playback...have you tried playing back thru the A&H desk (ie copy the wavs to thumb or SSD and play back using the A&H's USB slot) ?

Possibility of project sample rate mismatch between DP and the A&H...but impossible as you said 48K for both ?

It's got me stumped too, but maybe try playing back the raw wavs thru another computer to confirm the hash is printed onto the program material...and isn't just due to wifi or Bluetooth being on in the new Macbook ?
Old 1 week ago | Show parent
  #5
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🎧 15 years
Quote:
Originally Posted by studer58 ➡️
Very odd, since you were obviously monitoring the input on cans as the recording took place ?

Too late now, but could you have recorded onto a suitably fast USB thumb drive or external SSD at the same time as the stream out to your Macbook ?

Is it possible the Macbook has its buffers set incorrectly for playback...have you tried playing back thru the A&H desk (ie copy the wavs to thumb or SSD and play back using the A&H's USB slot) ?

Possibility of project sample rate mismatch between DP and the A&H...but impossible as you said 48K for both ?

It's got me stumped too, but maybe try playing back the raw wavs thru another computer to confirm the hash is printed onto the program material...and isn't just due to wifi or Bluetooth being on in the new Macbook ?
Yeah, that was one of my first thoughts too. Took the files down to my desktop machine in the studio, played back through my Apogee interface. Same problem. It’s definitely printed.

I think with these A&H boards you have to choose between the thumb drive method and USB connection to a computer — you can’t do both at once. Though perhaps I should check the manual one more time to verify that.

Fortunately, the band director says there’s time for a re-do next week. Needless to say, this time I’m going to be playing back after every take.

Another thing I could do for extra security would be to run the front stereo pair out to a Zoom recorder. Then at least if the USB connection goes squirrelly again, I’ll have something to show for it, even if it’s not a perfect mix. I haven’t had to think this way for a long time — guess I got complacent.
Old 1 week ago
  #6
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🎧 10 years
Maybe hunt down the A&H forum/discussion groups and see if other users have experienced this ?

Your idea of saving to an additional recorder is sound practice...and investigate whether simply recording to a fast thumb drive or attached SSD is a possibility, as you should be able to play back immediately through the board from the drive, rather than needing to record to DP directly ?

Seems to be a disparity between what the A&H can do theoretically and how it behaves in practice....are there any mixer firmware updates yet to be applied to it ?

Try to replicate conditions as closely as possible to the failed session (at home)...and see if you can provoke the same condition, then focus on eliminating it. Perhaps there's a DP bug or latest edition update...and check their forums too, for any 'field user complaints or reports'?
Old 1 week ago
  #7
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JCBigler's Avatar
 
🎧 5 years
This sounds to me like either a sample rate mismatch or a bad USB cable.

How are you monitoring the recording as it comes to the computer? You might have to set up a pair of return channels from the computer to the console to monitor the stereo/solo bus of the recording.
Old 1 week ago
  #8
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No backup and no monitoring? That's living on the edge, regardless of the culprit...
Old 1 week ago | Show parent
  #9
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🎧 5 years
hard to diagnose... - can you replicate the error? then try to find the source by systematically changing settings, from buffer size to drivers to using an older software version to swapping cables, changing clocking scheme etc.



[i recall one session in which for some strange reason i couldn't get one preamp going, no matter what (and i never found out why although i did try for much longer than the entire recording lasted) - i was a bit more fortunate than the op as i could cut down on channels so i didn't lose the recording but it was embarrassing as i was, contrary to my habits, operating on a rather minimalistic approach which didn't leave much room for errors...]
Old 1 week ago | Show parent
  #10
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🎧 15 years
Quote:
Originally Posted by studer58 ➡️

Seems to be a disparity between what the A&H can do theoretically and how it behaves in practice....are there any mixer firmware updates yet to be applied to it ?
The thing is, I’ve been using the A&H exactly this way for several years, including probably 10+ gigs and many hours of recording. That’s why I was caught off guard. I’m familiar with how it behaves in practice. Or thought I was.

Firmware update is an interesting point. Come to think of it, one difference with this session is that the laptop I had previously been using with this QU-32 had been running Mojave. The new one is running Catalina. Maybe the board needed an update to play nice with the newer version of Core Audio? I’ll check into that.

Quote:
Try to replicate conditions as closely as possible to the failed session (at home)...and see if you can provoke the same condition, then focus on eliminating it. Perhaps there's a DP bug or latest edition update...and check their forums too, for any 'field user complaints or reports'?
Yup, all good advice. I do have a QU-16 at home — an earlier generation than the school’s unit, so not quite apples to apples, but I can at least see if the problem replicates with it. If not, then I think the USB cable becomes the more likely culprit.

What I might do for the rescheduled session is bypass the board and bring my remote 16-channel rig (Focusrite Clarett + Audient ASP-880). That way I can set up the session at home and test it, so all I’ll have to do on site is set up the mics and plug them in. I’ll still want to stop and verify success after at least the first take, but it would reduce the scope of potential errors a bit.
Old 1 week ago
  #11
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🎧 15 years
Have you been able to recreate the problem in any way? What app was running on the computer, recording the audio?
Old 1 week ago
  #12
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🎧 5 years
This is really a mystery - I've never heard of any of the proposed causes creating anything like digital 'hash' so bad as to make a recording 'unusable'.

Have I just been incredibly lucky?
Old 1 week ago
  #13
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mpdonahue's Avatar
This may be a stupid question, but have you checked your buffer sizes?
When you re-install often these will get set back to default.
All the best.
Mark
Old 1 week ago | Show parent
  #14
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🎧 15 years
Quote:
Originally Posted by philper ➡️
Have you been able to recreate the problem in any way?
Haven't had time to take a serious shot at it -- will probably get to it over the weekend.

Quote:
What app was running on the computer, recording the audio?
It was Digital Performer 11.02. Same app I've always used with that board, though the last time I did this gig it was DP 9.5 on a laptop running Mojave (or maybe even High Sierra, at that point? -- it was almost two years ago).
Old 1 week ago | Show parent
  #15
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🎧 15 years
Quote:
Originally Posted by M50k ➡️
This is really a mystery - I've never heard of any of the proposed causes creating anything like digital 'hash' so bad as to make a recording 'unusable'.

Have I just been incredibly lucky?
Possibly. I was, until yesterday.

I mean, I literally have not had a problem of this kind since the early 2000s, back in the bad old days of proprietary PCI cards and frontier Firewire. I've gotten spoiled. This was a rude and probably useful awakening.
Old 1 week ago
  #16
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Here's a short sample of the audio to illustrate what the issue sounds like:

https://www.dropbox.com/s/aeysyxsah2...ts%20.mp3?dl=0


BTW, thanks to all of you chiming in to help. I appreciate it a lot.
Old 1 week ago | Show parent
  #17
JaL
Here for the gear
 
🎧 10 years
Quote:
Originally Posted by nightchef ➡️
Here's a short sample of the audio to illustrate what the issue sounds like:

https://www.dropbox.com/s/aeysyxsah2...ts%20.mp3?dl=0


BTW, thanks to all of you chiming in to help. I appreciate it a lot.
This thread might give some clues: https://community.allen-heath.com/fo...usb-b/page/12/
Old 1 week ago | Show parent
  #18
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🎧 15 years
Quote:
Originally Posted by JaL ➡️
It might indeed. Mind: blown.

So if I’m grokking the gist of those 21 pages correctly, it’s that:

1) Any computer with an Intel USB3 chipset is likely to have this problem, and if it does, there’s basically nothing that can be done about it—some folks seem to have had success using a USB3 hub with a USB2 port as a sort of buffer, but it’s not clear that this is a reliable solution.

2) Even though A&H has known about this issue for years, they designed their newer SQ series boards with the same USB2-only port.

OK, well, I guess I’m definitely bringing my own gear to any further recording gigs at this school. That is, unless I can get hold of an early 2010’s laptop just for using with A&H stuff.
Old 1 week ago | Show parent
  #19
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🎧 5 years
i don't want to seem cynical but fact is that you don't need usb3 to transfer audio files unless you use a ridiculously high sampling frequency and/or need to transfer an unbelievable number of channels - my rme madiface xt does actually need usb3 to transfer up to 196 input channels and as many output channels at single speed...

in short: don't blame a&h for using 'oldish' usb2!
Old 1 week ago
  #20
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🎧 15 years
I read that AH thread and it seemed like the people who got their systems working either used old "true USB2" computers and/or they upgraded the firmware of the console (and the AH driver if they are using a PC)?

Last edited by philper; 1 week ago at 06:56 PM..
Old 1 week ago | Show parent
  #21
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🎧 15 years
Quote:
Originally Posted by deedeeyeah ➡️
i don't want to seem cynical but fact is that you don't need usb3 to transfer audio files unless you use a ridiculously high sampling frequency and/or need to transfer an unbelievable number of channels - my rme madiface xt does actually need usb3 to transfer up to 196 input channels and as many output channels at single speed...

in short: don't blame a&h for using 'oldish' usb2!
I wouldn’t, except that I’ve never heard of any other company’s USB products having this problem. For instance, I have a first-generation Focusrite Scarlett 18i20 that must be more than a decade old at this point. USB-3 didn’t even exist (or at least wasn’t available to consumers) when it was designed. And yet that Scarlett plays just fine with that same 2020 Macbook Pro that had the problem with the A&H. So apparently it’s not an inevitability that older USB machines will fail in this way when connected to computers with newer USB ports. It must have something to do with the specific way the USB-2 on the A&H boards is configured.
Old 1 week ago | Show parent
  #22
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🎧 10 years
last entry on the linked thread reads.

Quote:
Wanted to say I upgraded firmware from an admittedly well out of dat 1.4 to 1,95 and it seems to have fixed the noise issue for me. Atleat based on one evening’s use. I am fond of my Qupac, makes a great compact home studio mixer but the noise issue was driving me bananas. Thought I’d broken the speakers. Anyhow all good just now. Thanks
so I guess that if you assumed that those updates work, it may not mean any given desk anyone hooks into, will have been updated. assuming those current updates are working in all cases, that is.
Old 1 week ago | Show parent
  #23
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🎧 15 years
Quote:
Originally Posted by Muser ➡️
last entry on the linked thread reads.



so I guess that if you assumed that those updates work, it may not mean any given desk anyone hooks into, will have been updated. assuming those current updates are working in all cases, that is.
I’m definitely going to recommend to the school that they do firmware updates on their A&H boards ASAP.

That said, there are a bunch of posts earlier in that thread from people who did firmware updates without any improvement. I think this may be a case where results vary because not everybody is actually experiencing the same problem, even though the symptoms are similar enough to make it seem that way.
Old 1 week ago | Show parent
  #24
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🎧 5 years
Quote:
Originally Posted by nightchef ➡️
I wouldn’t, except that I’ve never heard of any other company’s USB products having this problem. For instance, I have a first-generation Focusrite Scarlett 18i20 that must be more than a decade old at this point. USB-3 didn’t even exist (or at least wasn’t available to consumers) when it was designed. And yet that Scarlett plays just fine with that same 2020 Macbook Pro that had the problem with the A&H. So apparently it’s not an inevitability that older USB machines will fail in this way when connected to computers with newer USB ports. It must have something to do with the specific way the USB-2 on the A&H boards is configured.

Quote:
Originally Posted by nightchef ➡️
I’m definitely going to recommend to the school that they do firmware updates on their A&H boards ASAP.

That said, there are a bunch of posts earlier in that thread from people who did firmware updates without any improvement. I think this may be a case where results vary because not everybody is actually experiencing the same problem, even though the symptoms are similar enough to make it seem that way.
sorry but as a tech, imo you have to adjust to the venue's gear, not the venue to your particular needs! besides, there are plenty of reason to never update a system that's properly working...
Old 1 week ago | Show parent
  #25
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🎧 10 years
Quote:
Originally Posted by nightchef ➡️
I’m definitely going to recommend to the school that they do firmware updates on their A&H boards ASAP.

That said, there are a bunch of posts earlier in that thread from people who did firmware updates without any improvement. I think this may be a case where results vary because not everybody is actually experiencing the same problem, even though the symptoms are similar enough to make it seem that way.
the more up to date you get with one piece of hardware, e.g. a newer computer, the more all the connecting devices may become out of compatibility with a more modern computer and OS.

firmware updated devices would likely usually be more compatible with a larger range of computers. so I'd expect a more up to date computer to be a cause of larger incompatibilities, than the other way round. probabilistically speaking.
Old 1 week ago | Show parent
  #26
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🎧 15 years
Quote:
Originally Posted by studer58 ➡️
Very odd, since you were obviously monitoring the input on cans as the recording took place ?
Not odd. One should monitor the output of the chain, not the input!
Old 1 week ago | Show parent
  #27
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🎧 15 years
Quote:
Originally Posted by brew ➡️
Not odd. One should monitor the output of the chain, not the input!
Yes—I’ve taken this lesson to heart now. I was lulled into a false sense of security by the number of times I’d used that basic setup without trouble, forgetting that when it comes to digital audio, changing anything potentially changes everything.

Quote:
Originally Posted by deedeeyeah ➡️
sorry but as a tech, imo you have to adjust to the venue's gear, not the venue to your particular needs! besides, there are plenty of reason to never update a system that's properly working...
I’m not sure I understand how your first sentence applies to the situation. Being able to record streaming audio from these boards is important to the school — it’s part of the reason why they bought them. So if a firmware update stands any chance of making that work better, they’ll certainly want to do it. It has nothing to do with my “particular needs”.

And for the same reason, I wouldn’t say the board is “properly working”.
Old 1 week ago | Show parent
  #28
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🎧 15 years
Quote:
Originally Posted by Muser ➡️
the more up to date you get with one piece of hardware, e.g. a newer computer, the more all the connecting devices may become out of compatibility with a more modern computer and OS.

firmware updated devices would likely usually be more compatible with a larger range of computers. so I'd expect a more up to date computer to be a cause of larger incompatibilities, than the other way round. probabilistically speaking.
I see what you’re saying, although in the linked A&H forum thread I seem to recall a few people reporting that a firmware update to the board had solved the problem for them. And I don’t recall reading that anybody reported experiencing the problem for the first time after a firmware update, though a lot of people were reporting that the update didn’t help. So it seems worth trying.

Anyway, my computer isn’t really all that up to date anymore. It’s a Mac with an Intel processor, almost two years old now—hardly bleeding edge.
Old 1 week ago | Show parent
  #29
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1 Review written
🎧 5 years
Quote:
Originally Posted by nightchef ➡️
I’m not sure I understand how your first sentence applies to the situation. Being able to record streaming audio from these boards is important to the school — it’s part of the reason why they bought them. So if a firmware update stands any chance of making that work better, they’ll certainly want to do it. It has nothing to do with my “particular needs”.

And for the same reason, I wouldn’t say the board is “properly working”.
as a visiting engineer, i don't think you can expect venues to keep their gear updated to the latest software: they may have their reasons for keep their gear as it is...
Old 1 week ago | Show parent
  #30
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🎧 10 years
Quote:
Originally Posted by nightchef ➡️
It might indeed. Mind: blown.

So if I’m grokking the gist of those 21 pages correctly, it’s that:

1) Any computer with an Intel USB3 chipset is likely to have this problem, and if it does, there’s basically nothing that can be done about it—some folks seem to have had success using a USB3 hub with a USB2 port as a sort of buffer, but it’s not clear that this is a reliable solution.

2) Even though A&H has known about this issue for years, they designed their newer SQ series boards with the same USB2-only port.

OK, well, I guess I’m definitely bringing my own gear to any further recording gigs at this school. That is, unless I can get hold of an early 2010’s laptop just for using with A&H stuff.
FWIW I've had similar cracks using an Echo2 usb interface on an iNtel usb3 port. On same laptop using the usb2 it's fine.
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