At a loss for how to stop pops and crackling

honkyjonk · 02-16-2013, 04:45 PM

Hey folks,

I'm running the last PPC mac (dual 2.7GHz) , OS 10.5

And a Motu 2408 w/ 424 card.

I can't figure out why I can't get it to stop popping. Just trying to back up 24 tracks (at 48K)

I have the buffer size all the way up at 6000 ms
and the block size up at 4048.

Obviously those should be enough. I'm not looking for excellent latency or anything. I'm just using Reaper to back up some projects.

Any suggestions?

roygbiv · 02-16-2013, 10:38 PM

Hey Honkyjonk

One possibility - is it possible you have some settings mismatched between the 48K and 44K? Sometimes I have had crackling and popping if Reaper was having to do a conversion between the two rates the fly - check to see if you have 48k checked all the way through in all the options.

just a thought.

Ollie · 02-17-2013, 03:49 AM

Is it popping during recording or playback or both? Are the artifacts appearing at the same places or randomly?

Quote:

Originally Posted by honkyjonk

I have the buffer size all the way up at 6000 ms

Do you mean media buffer size in Preferences or a buffer size setting in the control app for your audio hardware? Media buffer size in Preferences only affects playback.

Quote:

Originally Posted by honkyjonk

and the block size up at 4048.

- Did you check the checkbox next to the block size setting?

On some hardware, a too high setting can introduce artifacts as well. If 512 samples doesn't improve the situation, block size is probably not the problem. Did you ever optimize that computer for audio? Airport, Time Machine, File Vault, Bluetooth, Coffee Maker all turned off?

honkyjonk · 02-17-2013, 11:06 AM

"Do you mean media buffer size in Preferences or a buffer size setting in the control app for your audio hardware? Media buffer size in Preferences only affects playback."

Ah, okay. It was during recording, because the artifacts are always in the same spot, i.e. recorded.

- Did you check the checkbox next to the block size setting?

Yes, at some point.

-"On some hardware, a too high setting can introduce artifacts as well. If 512 samples doesn't improve the situation, block size is probably not the problem. Did you ever optimize that computer for audio? Airport, Time Machine, File Vault, Bluetooth, Coffee Maker all turned off?"

I started with 512, as that was the defualt, and just kept doubling it.
But anyway, it sounds like I need to find the buffer adjustment in my cuemix software? (That's the program that adjusts levels at the MOTU 424 card)

I'll have to check all those programs I suppose.

As for the 48 vs. 44 sample rate question, where are all the places to verify that it's definitely 48?

Ollie · 02-17-2013, 02:18 PM

If SRC is being applied within REAPER (which would cost CPU power), a little blue [i] icon should appear on the affected items.

TimOBrien · 02-17-2013, 02:20 PM

Are you recording to the boot drive or to a proper secondary drive?

honkyjonk · 02-17-2013, 03:01 PM

Okay,

I found one option where 44.1 was selected instead of 48K, and that seems to have solved it for the most part.

There are still, however, pops that are being recorded, only one little one every minute or so.

BTW, a little more background: I have a bunch of stuff on an older Otari Radar II that is using TDIF digital cables into the MOTU 2408, then a firewire connection to the 424 pci card. It's clocked to the Radar's word clock.

As far as how to adjust the buffer size on the PCI card's software, there isn't any place you can do that as far as I can tell. In Reaper instead possibly?

Anyway, the upshot is, there are definitely pops recorded in the transferred tracks.

And yes, I'm recording to the boot drive. Hmmmmmm . . . .

Ollie · 02-17-2013, 03:21 PM

Quote:

Originally Posted by honkyjonk

As far as how to adjust the buffer size on the PCI card's software, there isn't any place you can do that as far as I can tell. In Reaper instead possibly?

You can request both a block size and sample rate from the device in Preferences->Audio->Device, just don't forget to check the checkboxes to activate the options.

Do you have another host software to test the general function of the outboard rig + 424 by chance?

TimOBrien · 02-17-2013, 08:48 PM

Quote:

Originally Posted by honkyjonk

And yes, I'm recording to the boot drive. Hmmmmmm . . . .

Just like with windows pc's, the Mac has to do a lot of other things (OS stuff, services, other apps running, etc.)

You REALLY want to run audio tracks and project from a second drive (and a third for sample libraries if you use them)
Smooth UNINTERRUPTED flow of data is your goal.

Get too much going on the boot drive and it can cause dropouts, clicks and pops.

serr · 02-17-2013, 10:17 PM

And the boot drive is a 5400rpm drive I bet. (ie. slow)

It will be important to optimize the I/O (hard drives) in this somewhat older system. Either 2 7200rpm drives (one with OS/Apps and the other for audio) or a single SSD. (A single SSD with OS/Apps/audio really does outperform 2 standard drives.)

$160 will get you a 240GB SSD (your 2.7Ghz G5 is SATA). Or scare up a couple oldish 7200 rpm drives for less than that. Use your external for storing stuff you're not currently working on.

Do this and that old computer will still do a lot.