buzzing when three 888/24's are connected, Help!

[poofboy]

Hello all... any insight would be appreciated.

I have an older TDM mix plus system. Mix core, mix farm, and one dsp farm card and three 888/24's. Computer is a G4 1.42 gHz with 1.5 gigs of ram.

whenever all three 888's are conected in any configuration... (one to each card or two to one card with a Y cable), I get a buzz on what the computer sees as interface three.

I have troubleshot this into the ground. Starting with just the mix core card in the computer then going through each 888/24... then each cable... then adding the mix farm card and doing the same... All the gear is fine on it's own. Every 888 is clean if it's the only one or one of only two plugged in. But the second all three are plugged in... in any order...the buzz pops up...and always on interface three... no matter which of the three 888's the computer sees as interface three. Even if I unplug the interface its getting the buzz from... it still buzzes like it's there. I'm pulling my hair out... please, please please... someone make me feel stupid... solve this puzzle for me.

thanks,

BB

[PTLance]

Have you tried not plugging in the inputs or outputs on the third interface. It might be something in your cabeling. Try switching second and third interface I/O cables and see if the buzz then switches to the second interface.

[poofboy]

yeah... tried that... buzz still exists on whichever interface the computer sees as #3. As for pulling inputs tried that too... still buzzes... as a matter of fact... even if I unplug interface #3 while pro tools is running it will continue to register a phantom bus on every non-existent interface #3 input. goofy huh.

thanks.

[Shawn Simpson]

I didn't see any mention of your clock cabling. Do you have the little BNC cables connected properly? (slave clock out of first interface to slave clock in to the second, then out of the second into the third)

[poofboy]

I don't have the BNC cables connected... I was informed that's for an external clock source only. I'm just using the internal clock source... is this wrong? would this cause the buzzing?

THanks.

[Shawn Simpson]

Yes, you were told wrong. The 888's require slave clock between them in order for it to work. Frankly, I'm surprised you can get more than one to work without some serious problems. So connect the little bnc cables that came with those interfaces and you should be good to go. That's an absolute requirement.

The only other thing I've ever seen that will cause an interface to make nasty noises was if you had the wrong interface type selected in the hardware setup. In my case, I had a 16bit 888 connected but selected 888/24 in the setup dialog. It made the interface go into a nasty little digital oscillation. Also, don't EVER disconnect an interface with the computer turned on, much less with Pro Tools running. That's a first class ticket to destroyed hardware.

[poofboy]

Thank you very very much... the bnc thing did it. You're the best.

BB