OT: Behringer ADA's versus Everything else...

[muzicman0]

I used to use my Saffire Pro 40's as Mic Pre's on my MOTU 2408. Worked great.

[Cary B. Cornett]

Peter,
...What of the FOH or Monitor engineer?

I was told by one source that the audio quality coming out of a "stock" SAC system - HDSP 9652, ADA-8000's, and WINXP was so good that they commented that they had never heard such great audio output previously.

There is either something else going on - or I am "more than likely" missing something here?

My first experience experimenting with a SawStudio system for a live stage musical (this was before SAC came out) was a real "ear opener". Compared to a low-budget analog board, it was like wiping the dirt off the glass. The clarity blew me away. This may have been even before I got my HDSP 9652, and would have used the ADA8000 converters. I was sure the difference was all about the mix "engine" in SAW.

At the present, my only concern would be the "60hz buzz in the output stage" that Philip was referred to. My question to Philip is, "How quiet does it need to be before this 60hz buzz can be heard?"

Low enough buzz levels might be masked by ambient noise in the hall, especially with the crowd present. I have discovered that some equipment has bad internal grounding design, such that unless you can go in and fix it inside the box itself, no amount of system ground "tweaking" will fix it. The next question is, are we sure the hum in only in the outputs, or does it get into the system earlier? If it's just the outputs, you might be OK for recording purposes (you DO sometimes record while running the mix, right?).

[Cary B. Cornett]

Its also possible [the hum is] inductively induced by other equipment in my rack, although I'm pretty sure thats not the case.

I suggest careful testing by process of elimination. Remove everything from the rack except your converters and check the outputs for hum. If it went away, put back one item at a time and test again. I discovered a very low level of induced him in my own system rack, and arranged the equipment to minimize it (could not completely eliminate it). Since the hum in my setup is pretty much down in the noise, I'm OK with it.

[mr_es335]

muzicman0,

I used to use my Saffire Pro 40's as Mic Pre's on my MOTU 2408. Worked great.

...I am very glad that the PRO 40's worked for you...as they did not for me...twice!!

The instrument input - though stated as 1 meg ohm, was checked at over 2 meg ohms. Even with the pad enabled, I was still getting a distorted input. Contacted them, but phone, and received no help at all.

The same can be said for ZOOM...and it appears that they are getting out of the interface market.

I am renting a Presonius Digimax FS and I will see how that goes.

[muzicman0]

Wierd, I had 3 of them at one point, with no issues. Good luck.

[muzicman0]

I'm curious how you measured the impedance of the input? Since Impedance is affected frequency you can't just hook up a ohm meter.

Also, what did you have connected to the mic inputs?

[cgrafx]

The next question is, are we sure the hum in only in the outputs, or does it get into the system earlier? If it's just the outputs, you might be OK for recording purposes (you DO sometimes record while running the mix, right?).

Just seems to be present in the outputs. I've not noticed it in any of the recordings we have done.

The hum was one of the things that popped out to me when I replaced my ADA8000's with the ADA82000's, since it wasn't present with the 1st gen boxes.

The amount of hum also varies from box to box and is made worse when dropping the input voltage on the AC supply side, which leads me to believe its an issue with the power supply falling just slightly out of regulation (which is a little odd for a switcher).

I'm fairly confident I could fix the issue with some additional filter caps added to the supply lines closer to the output stage.

[TomyN]

Hi,
the ADA8200 has a switch-mode power supply, so hum should be no issue there.

Tomy

[Dave Labrecque]

Hi,
the ADA8200 has a switch-mode power supply, so hum should be no issue there.

Tomy

And yet...

[cgrafx]

Hi,
the ADA8200 has a switch-mode power supply, so hum should be no issue there.

Yes I'm aware of that, but the hum is present and when the AC voltage is dropped the hum increases. Without a schematic I can only guess as to the reason but it leads me to believe there is still something falling out of regulation sufficient to get into the output stage of the ADA.

I actually purchased a spare 8200 to tear apart and reverse engineer at least part of the schematics to try and identify why the hum is present.

I have also been looking at how to add a buffered mic split and need the input stage schematics to determine the best way to incorporate the additional circuitry.