Noise on 828II ADAT inputs

[mattmundesley]

This is a continuation of a post a put on the DP forum originally, so apologies to those that have read it before but I feel that this may be the more appropriate place for this discussion. I also hope (with due respect and thanks to colleagues who responded on the DP forum) that there might be someone here who has had a similar problem or can point to a possible solution.

My original post as follows:
My set up:
Powerbook G4 1.5 ghz 2gb RAM OSX 10.4.8
DP5.11
2x 828 mk2's
1x 828
2x Behringer ada8000 a/d convertors
Latest motu firewire drivers installed

Hi,
I hope someone can help with this. I am having acute problems with the above set up, I have set one of the behringer units as master clock driving 828#1 via adat, wordclock drives 828#2, ADAT optical clock to the next behringer and spdif clock to the mk 1 828.This is a configuration I have used succesfully to record up to 44 tracks simultaneously in the past. The problem is that when I launch DP I get all sorts of horrible spikes and clicks on the adat inputs of both mk2 828's (the analog inputs are fine). This problem only seems to be there when DP is running and goes when I quit DP I have tried changing firewire and adat cables with no luck, and I have tried running an 828 as master which seems a little better but still not very stable.
Any help or guidance would be greatly appreciated as I have a concert to record on Monday evening!

Many thanks,

M.

I have now replaced the Behringer ADA8000's with Focusrite Octopre LE's but still have exactly the same fault on the ADAT optical inputs of the 828 MkII's.
Based on my continuing attempts to resolve the problem I would add the following details:
The problem doesn't after all seem to be related to DP but just builds up over time.
The problem begins with a slight high pitched whine from the 828 with occasional clicks on ADAT input #1 this builds over time, usually an hour or so, to the point where there is what sounds like awful 'static' blasts across all 8 ADAT inputs which clip continuously. Disconnecting the ADAT input removes this noise but it appears again when reconnecting it. The whine can be removed by restoring factory defaults on the 828's but the static can only be removed by changing the clock source to ADAT optical, but it eventualy returns. I have tried clocking to various sources including an MTP AV but the problem persists.
Attempts to isolate the problem to a particular 828 or ADAT interface have been entirely unsuccessful. Running just one 828 with an ADAT interface also exhibits this problem and I have tried this with both 828 mk2's.

If anyone can help I would extremely grateful.

MM.

[mattmundesley]

Hi,
Posting this reply for the sake of the archive in the hope that it helps someone else.
The problem turned out to be overheating! I had the units (2 x 828 mk2's and 2 x Focusrite Octopre LE's or 2 x Behringer ADA8000's, the problem was consistent whichever I used) In a Warwick "Rockbag", a padded 19" Rack/bag, because the 828's were happy when first turned on and the problem became worse over time Mark Gordon at Musictrack (UK MOTU Distributor) hit onto the idea that they may be getting too warm. So I moved them to a larger rack with 1U of space between each unit and the problem went away! The curious thing is that I have used the units in the Warwick rackbag before and had no trouble, albeit that was a couple of years ago so what has changed I don't know.
So all ended happily and the job got done but thanks Mark Gordon at Musictrack for his infinite patience with my increasingly desperate phone calls, and for figuring it out for me. I hope that this post might help someone else in the future.

Regards,

MM