888|24 Monitor Hiss

[HSLand]

I have a MixPlus system with an 888/24.

There seems to be a noise floor or hissing issue in my monitors. I've had a Multiface and a Fireface and they were both literally *dead silent*. The PT rig seems to have an underlying hissing issue, and I'm not sure I could even call it a 'noise floor' since when moving any faders, the noise doesn't come up with it. It's just *there* no matter if all faders are set all the way or not.

I remember an older Presonus FirePod having the exact same issue, the EXACT same noise. I can't really explain this but funnily enough, when I used the FirePod strictly as I/O and used another interface (Multiface or FireFace) for monitoring, the issue was gone.

So the noise isn't inherent in the recording at all since I can take a recording from that system and it sounds fine on another. This is more of a side effect of hardware, or something.

[studiojimi]

got something on the 2bus? using a lot of compression and limiters in your mix cumulative amping

[HSLand]

The hiss happens when my monitors are connected to the interface at all regardless if I'm in Pro Tools. I found that by changing the Sync mode to Digital, the hissing stops 100%. I also find that enabling DAC Muting stops it, but only when nothing is playing back and it starts again once I'm playing a track. The only other thing that helps is using the trim screws on the front of the 888|24.

I'm wondering why some interfaces do this and some don't.

[HSLand]

I'm using a revision C 888/24. I believe the converters were upgraded starting at revision J. I wonder if that has something to do with it.

It doesn't really make sense that the problem occurs ONLY when I've got monitors connected to the 888/24, and the same goes for that Presonus interface as well. These interfaces all sound fine when using it as a satellite I/O box via adat/digital or just when using it normally to send something over to a processor, etc.

What in the world could this be?

[Craig F]

old noisy DACs, that's my bet. it's what 15 years old?
I don't remember if they were noisy but I've had DACs fail and get noisy

[John_Toolbox]

I used to run the old whiteface 16 bit 888's, all the way up to the last revision that had 24-bit DA converters (the early 888/24's had 24bit bit AD converters but only 20-bit DA's). None of my 888's ever hissed like that, so I don't think your problem is the revision. Unless it's caused by a bad cabling or a ground loop problem, I think Craig is right... it's probably just worn out. The good news is that 888's are a dime a dozen on the used market.

[HSLand]

I fixed the problem. Sort of.

I turned the trim controls all the way down on the front panel with a screwdriver until I heard that clicking sound and the hissing stopped. I wouldn't think a trim control would do that but the problem seems to have cleared up.

Is this normal behavior?

[Craig F]

clicking, DACs are bad

[HSLand]

The clicking is a physical sound that lets you know the trim knobs have been turned to their extremity.

[John_Toolbox]

Have you tried re-calibrating the 888 now that that you've moved the pots? While they control digital levels, the trim controls are still technically analog potentiometers. The effect a "dirty pot" has on digital will sound different than the scratchy noise that it would on an analog console, but perhaps that's what you were hearing? Twisting them back and forth to clear the dust out of them might be all that is needed. You should be able to confirm if this is the issue by trying it one channel at a time. If you calibrate channels 1-2 and the noise increases only on channels 1-2, then I would try trimming the pots back and forth to clear them. If you calibrate channels 3 and 4, and the noise comes back on outputs 1-2, then it's probably a bigger problem and I would replace the 888.