Multi Out, 2 Channel Master In

[stevelees]

Hello, I am trying to get my head around sending 24 tracks of DP7 out of my 24I/0 to a summing mixer, through effects and back into either the 24I/O or the 2408, and record the track on BIAS Peak. I am looking at this as an alternative to recording the 24 out onto a DAT for mastering.

My setup is a Mac Pro with 8 cores, 6GB RAM and more HD space than I care to mention. So I am assuming the Mac panhandle both tasks (DP7 out and PEAK in) and in basic testing all seems OK, but..,

I notice on the metering in PEAK I see noise around 80-90db down, even with the signal being gated, so I am assuming this is some kind of audio leakage within the MOTU system?

Anyway I am wondering what everyone else here does when mastering to 2 track in the box....cheers.

[bayswater]

The -80db noise may be a clocking problem. Are the 2408 and 24i/o synchronized?

[stevelees]

I would assume so as they are both set to use the internal clock of the PCI card, unless I am wrong ??

[bayswater]

Yes, according to the manual that is the case. And I guess you are using analog out to the summing set up and analog back in. If there is a digital connection to an external device lie a digital mixer etc, involved, that's a potential source of the noise.

I've never been able to get inputs free of low level digital noise when using two MOTU units unless I have the clock on one slaved to the other via a BNC cable. There is always one channel that has a square waveform at -80db, which is what I think you are seeing? This makes no sense, and shouldn't happen according to the descriptions of these devices in the various manuals. But sometimes its easier to just do something that works instead of hunting down the cause.

[stevelees]

Yes, according to the manual that is the case. And I guess you are using analog out to the summing set up and analog back in.

That is correct yes!

If there is a digital connection to an external device lie a digital mixer etc, involved, that's a potential source of the noise.

No not in this case, all analogue...

I've never been able to get inputs free of low level digital noise when using two MOTU units unless I have the clock on one slaved to the other via a BNC cable. There is always one channel that has a square waveform at -80db, which is what I think you are seeing?

Absolutely bang on, one channel is most definitely showing a higher level of noise than the other.

This makes no sense, and shouldn't happen according to the descriptions of these devices in the various manuals. But sometimes its easier to just do something that works instead of hunting down the cause.

So you say by syncing them to each other through the external clock connections will solve the problem?

[bayswater]

So you say by syncing them to each other through the external clock connections will solve the problem?

I don't know. It solved mine which looked very much like yours. I connected the two units with a BNC, left one unit set to "internal" and set the other to 'word clock'. The noise on the meter disappeared.

[stevelees]

So you say by syncing them to each other through the external clock connections will solve the problem?

I don't know. It solved mine which looked very much like yours. I connected the two units with a BNC, left one unit set to "internal" and set the other to 'word clock'. The noise on the meter disappeared.

Hmm, I will give that a go when I get home tonight, thank you for the tip! Will let you know how I go, I have also put in a tech help request with MOTU so I will see what they say too.

[bayswater]

Hmm, I will give that a go when I get home tonight, thank you for the tip! Will let you know how I go, I have also put in a tech help request with MOTU so I will see what they say too.

I'd be very interested to hear what they have to say about the low noise levels.

[stevelees]

I'd be very interested to hear what they have to say about the low noise levels.

Well, it seems MOTU are too busy to answer my tech request.....so I am still at a loss.

I have tried connecting the two MOTU devices with a clock cable, but I have had no luck getting that to work at all...perhaps I should sell the mOTU units and buy something else...