nasty distortion from interface/converters

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nasty distortion from interface/converters

Postby andyforssman » Fri Oct 12, 2012 7:38 pm

Howdy all
Hoping someone can point me in the right direction to resolve the following;

I m getting a horrible digital crackling/distortion occuring every hour or so when recording and mixing.
My set up is as follows:
02r96 > (via adat) Focusrite saffire 26 > (firewire) iMac > ProTools/Logic > then back to 02r96 via the interface's adat outs.

I have been getting around this by turning the interface off, then back on. Once the DAW recognises the interface it functions fine.... for about an hour or so before doing the same.

I assume that the Focusrite is struggling with the audio going in and out back and forward between the console and the DAW???

Any suggestions appreciated.
Thanks
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Re: nasty distortion from interface/converters

Postby Text_Edifice » Fri Oct 12, 2012 7:57 pm

Hi Andy,

just to eliminate the obvious, is the o2r or the saffire the clock master?
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Re: nasty distortion from interface/converters

Postby ChrisW » Sat Oct 13, 2012 7:49 am

I had a similar issue when sharing firewire on an iMac. Do you have anything else happening on the FW buss... hard drive, midi?
My audio interface (Aurora) didn't like to share FW with anything.
It would work ok for a short period, then break down to extreme bit crushed type sound.
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Re: nasty distortion from interface/converters

Postby Chris H » Sat Oct 13, 2012 8:22 am

Also to eliminate another possible cause, try another firewire cable. When they go south, this is often the result
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Re: nasty distortion from interface/converters

Postby andyforssman » Sat Oct 13, 2012 9:59 am

Thanks for the responses
The clock master is saffire.
As for firewire .. I have external glyph hard drive connected to FW400 (rear of iMac), Saffire connected to FW800 (rear of iMac).

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Re: nasty distortion from interface/converters

Postby Text_Edifice » Sat Oct 13, 2012 10:03 am

If the iMac's are built like the macbook pro's the 400 / 800 ports may share the same bus – is it a recent problem or have you added either the o2r or saffire to your setup recently?
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Re: nasty distortion from interface/converters

Postby Gian » Sat Oct 13, 2012 11:13 am

Try increasing the buffer size.
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Re: nasty distortion from interface/converters

Postby Drumstruck » Sat Oct 13, 2012 11:50 am

I had a similar distortion problem (with a completely different system) that also went away with a restart - when I clocked the 3 ADACs together using a BNC daisy chain (instead of S/PDIF) it ceased. ;)
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Re: nasty distortion from interface/converters

Postby Chris H » Sat Oct 13, 2012 12:39 pm

Is your mac on OSX 10.8?
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Re: nasty distortion from interface/converters

Postby Text_Edifice » Sat Oct 13, 2012 1:34 pm

In terms of fault finding here's what I'd do (and I apologise if this is pitching way too low).

Make sure you've got the latest version of SaffireControl, firmware etc. and are powering on in the suggested order (interface first, then mac). I'm sure you've done this.

Check your audio midi setup and make sure the saffire is recognised and working as you'd expect (e.g. clock source selection / sample rate matches what you see in SaffireControl).

Pull the harddrive off the fw 400 port (easiest possible fix).

If no good, does the saffire work properly sans O2R? If so the problem is either between or with the O2R (clocking / dodgy adat card or connectors / dodgy d/a converters).

By process of elimination if you're still having problems it's probably the saffire or the the mac and in either case you'll need to either swap out the interface / try it on another machine.

As an aside (and probably not relevant), core-audio can be a bit fussy with FW interfaces if you ask it to do too much at the same time (e.g. running a DAW, iTunes and streaming or buffering audio / video from the web). I've seen this result in bursts of noise / distortion and other weirdness.
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Re: nasty distortion from interface/converters

Postby ChrisW » Sat Oct 13, 2012 4:03 pm

It depends on the audio interface, but some wont share fw with any other device.
I think the iMac fx is one buss.
Only way to quickly test is to remove the Glyph completely (unplug fw cable), then work as you normally do with the Saffire and see if the problem goes away. If it does, you have your culprit.
I'm using an Apollo with my imac and have a Lacie TB drive. I plan to get the Apollo TB card too soon.
I found FW was a hassle on a budget (eg: imac)
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Re: nasty distortion from interface/converters

Postby andyforssman » Sun Dec 30, 2012 9:28 pm

Thought I'd better update where I am at with this issue. I am still a little unsure as to the actual cause but all seems to be going well since I began turning the interface off then on again before opening PT. Touch wood.
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