192 Output Stage Oddities / D. Clementson question?

[fab]

Hi all.

I'm puzzled, I need help. Argh.
I spent a lot of time on the phone with tech support yesterday.
They're sweet and eager to help but totally clueless on this issue, SO:

Did anybody else notice that the 192's HOT, COLD and GROUND pins all show continuity between each other?

Frankly, I couldn't care less, if it wasn't for everything else in my patchbay absolutely freaking out when I plug the 192 in. (Mega drop in level, low pass filter like artifacts, crazy transient distortion, showing up on everything that is sharing a bay with te 192)

By the way, everything had been working just lovely for about a year prior with RME converters in place of the 192s, using the very same DB25 breakout cables. (The pinout is identical, I checked)
The 192 inputs all test fine. Only the output show this behavior.

I did pull the 192 out of the bay, and disconnected it from everything else in the studio, and it still showed the same testing results.

I'm floored.

Also, anybody knows the output impedance of the 192s?

Basically, I'm stuck with a useless studio until I get some info on this.

What gives?

Ciao,

Fab

[doug_hti]

I had (what seems) nearly the same problem a few months ago.
It was fixed by replacing the 192. It probably has to do with the AD or beyond.
You may want to put in a call to techsupport and get a RA# or replacement.
Muffled sound thread

[doug_hti]

And to add to what I said....I did not have a normalled patch bay...but I couldn't get anything good into the system....so I don't know what would have happened, had I had a fully loaded patch pay half normalled or normalled.
I'm only addressing the low pass filter and distorted transients....

[miwokman]

Did you try sending a signal out the 192 and back in and listening to the result (obviously not through the patchbay)? If this works fine, then it probably has something to do with the differential balanced output of the box and interaction with your patchbay - not a bad 192. It's a known fact that the 192 does not like unbalanced connections (note the back panel silkscreen stating - leave negative terminal unconnected) nor floating ground schemes that don't quite reference back to a common earth ground.
I think I read somewhere that the output impedeance is 50 ohms.

Good luck

MWM

[FajitaTone]

50 ohm 3-wire AES? I could have sworn it was 110 ohm and 2 wire (bnc) is 75 ohm.

Please correct me if I'm wrong. thanks.

[img]images/icons/smile.gif[/img]

[FajitaTone]

I've been working too long... this thread is about the analog to digital and back conversion.

[img]images/icons/shocked.gif[/img]

[fab]

Ok,

So it's clearly a problem with the way Digi implemented the balancing of the box and my patchbay.
I just tried every 192 in the building and they all show the same behavior.
So where do I go from here?
It works with every other converter I could put my hands on.
Only the 192 does this. Again it worked flawlessly for the longest time.
I also tried to figure out which one of the pins truly cause the problem.
IT"S NOT THE GROUND. I'm floored again. Everything is fine when the ground of the 192 DB25s is hooked to the bay. It's when I connect the HOT pin that everything on that bar gets loaded and goes to mush.

I'd love to hear a pointer from whomever came up with that scheme, and his solution on how to hook his design up with a balanced, normalled patchbay.

Let me rephrase: I NEED to hear a pointer from whomever came up with that scheme, and his solution on how to hook his design up with a balanced, normalled patchbay.

Thanks.

fab

[fab]

I hate to be a pest, but COULD SOMEONE FROM DIGI PLEASE COMMENT ON THIS ???

I called tech support three times yesterday with a simple question:

"Is it normal that the HOT, COLD and GROUND pins of all channels of a 192 interface should show continuity to each other?"

(Hence wreak avoc on my patchbay, bla, bla,bla)

Three tech support guys said: "ehhhh, I don't know"

Let's escalate this shall we? I was promised a call which didn't come.
I'm sitting stupid with my soldering iron in my hand.

I just need to know, and also know why while we're at it.

Thanks.

Fab

[fab]

Ok,

Here's the news: I was graced by a call from the lovely Stan Coty @ Digidesign, who took time to explain to me the ins and outs of my situation.
(That's what I call tech support, by the way)

To summarize a really long conversation:

-1 Yes, it's ok to measure continuity between HOT/COLD/GROUND, it's done by design, it's a byproduct of never letting the 192 be a high impedance box. (Stan put it in a much more interesting and detailed form, but that's what I retained, there was a real flood of info)
So although it seemed weird, it's not what's causing my rig to freak out.
Fair. I'll put my tester back where it belongs. In the closet.

-2 To make a long story short, I'm doing some really slick but absolutely not kosher stuff with my bay, that the 192 just doesn't like to see.
I got away with it before, with the RMEs, because they had a higher output impedance. The 192 replacing the RMEs basically showcased the shortcomings of doing what I'm doing (See below for a description)

The solutions:

1-Raise the output impedance of the 192 and I should be fine, but I risk altering the performance of it. Long cable runs aren't really a problem for me, I live in a closet, but I don't want to alter the sound of the box.
That will be my first try though.

2-Break my normals, and manually patch the stuff when I need it. And that, my friends, will be my last resort, because the way I have it now is SOOOO nice.
The set-up:

I have every mic pre normalled to its best matched compressor, which in turn is normalled to the 192 inputs, AND I also have the outputs of the same 192 normalled to the inputs of the compressors.
So: for tracking, it's a direct path from the mic to the track (But I can change the set-up by hand-patching when I have time to try different combinations)
And, I can also insert any of my compressors on my PT tracks, without patching.
I switch songs many, many, many times a day and I use outboard on every single song. Repatching every time would really be a pain in the ass, hence the system I devised.

Voila.

That's the not so short of it.

Thanks Stan for being diligent and patient with me.

My iron is hot, impedance, here I come,

Ciao,

fab