HD 192 bass-lite? Impedance mismatch?

[D Clementson]

There seems to be some confiusion about the output impedance, output buffering, and low-frequency rolloff on the 192 I/O. Let me try and clear some of this up:

The 192 I/O has a very high quality buffer on the DAC outputs. It uses the same Meitner discrete class-A topology as the ADC driver, only in a higher power and short-circuit protected configuration.

It is essentially a dual-mono output vis-a-vis the '+' and '-' terminals, and does NOT automatically compensate for unbalanced connections. This is because those auto-unbalance circuits are notorious for destroying pulse fidelity on balanced connections. The cable capacitance looks like a "short" to the fast pulses, and so the auto-unbalancer kicks in and distorts the pulse shape. This is why we suggest that you use only the "+" leg when driving unbalanced loads. A note to this effect is silkscreened on the back panel.

Its output impedance is 50 ohms per leg, so it is capable of driving extremely demanding loads.

The frequency response of the DAC, including buffer, has been measured flat to within 0.15 dB down to 10 Hz, and the -3dB point is probably about 1Hz (I'm not sure because the Audio Precision can't measure that low). There is a DC removal servo whose corner frequency is 0.1 Hz.

I have no idea what is causing the problem with the original poster's analog tape transfer, but I very much doubt that it has anything to do with the 192 I/O output driver.

DC

[c-tone]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR> <HR></BLOCKQUOTE>

So Dave,

In practical use, how do we "only use the + leg when driving unbalanced loads"?
Could the pin 2 or 3 hot issue cause such a low frequency loss?

thanks

[RKrizman]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by D Clementson:


I couldn't tell you what's causing the LF loss without knowing all of the setup details - including cable wiring. If I were troubleshooting it, though, I'd start by checking the cable pinouts.


DC<HR></BLOCKQUOTE>

Dave, what would it take to get you and Mixerman on the phone together? Maybe it would be worthwhile for a knowledgeable Digi rep to check things out at his session, if he's willing. MM isn't some hobbyist--he represents the top echelon of professionals using your gear and would certainly warrant some on-site trouble shooting if he's not getting the published specs out of the converters. And likewise, if there is some real-world deficiency with the 192 that's just coming to light, this would be the time to find out.

(Hey, for years I thought those Firestone tires were just fine.)

[rtcstudio]

Somebody correct me if I'm wrong, but my impression of Mixerman is that he is someone who hates digital recording, and hates ProTools in particular.

Seems like whenever I log on to his website there is something extremely derogatory about ProTools, and that he is looking for ways to diss it. He grinds his axe with a vengeance.

I would like to get to the bottom of this, but I would DEFINITELY not take his results as being objective at all. There are a lot of PROS out there who think that it is blasphemy to use ProTools at all. I second the post that we need to hear from some other ProTools users who have had transfer problems before we react globally to this one experience.

[shaggy]

How about Studio D and their Studer & 9098i ?

[Brad Cobb]

I’ll try to set the record straight. I was at that studio with Mixer Man the other night. I’m not sure if he hates digital and/or Pro Tools, it does not seem so, he did have a HD rig for editing. I did hear the comparison, and it was, as he said.

I thought the 80 to 100 hz had less energy on the HD rig and opposed to the Studer. It was possibly shelved and at what "hz" I don’t know, it did have less "weight". If you have ever done an analog to digital transfer, you know what I’m talking about. I did hear it and it would not have ruined my day, it is par for the course.

Now having said that, I have to say that the Radar came back as close as anything could to the Studer. It was nice to see that kind of replication. I started to get bummed about my HD rig and then I thought about this. First off, at the end of the day the difference was small and secondly the Radar is 12 tracks @ 96k without a mixer and plug-ins and cost around 12,000. Pro Tools is 64 tracks @96k with very useable mixer and is a monster editor and cost under 16,000 with cpu and the HD3 and a 192 interface.

I do not feel (along with all the studio techs I’ve talk to) that it was an impedance mismatch, all the specs look correct for each piece of gear. The two recorders just sound different. In my fantasy world I would have liked to also had a 3M-79 and an Otari-MTR90 on that session to compare, cause they all sound different.

I talked to the guys at IZ (great guys) and they said that their converters are trying to be as linear as possible, he did say that they use very "expensive" analog circuits. If the guys at IZ Technologies ever made the added feature called "Click Tracy" then, maybe these types of productions would use their Radar exclusively. The bottom line is, the Radar is a really great sounding box as is Pro Tools HD. It comes down to what do we want to work on and what can we afford? I guess the 5 or 6 Radar’s would be the cheap part of the equation compared to a rebuilt 64 input 8128 or 8108.

I’ve been tracking on my HD and I’m really enjoying the "day-light" in the bottom. I feel the bottom is way more musical now than it was before on my TDM 1 rig. I do not spend so much time carving out the low end in my mixes. I’ll just get back to work.

Peace, Brad

[D Clementson]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by RKrizman:


Dave, what would it take to get you and Mixerman on the phone together?

<HR></BLOCKQUOTE>

I'm happy to talk to any customer as long as they're reaonably polite and genuinely interested in solving a quantifiable technical problem. However, I do NOT care to waste my time engaging in some endless debate about subjective aspects of analog vs. digital recording, nor do I want to listen to a bunch of vitriolic Digi bashing.

DC

[Corey Shay]

Pindy mentioned a polarity reverse... I've found that on kick drums, polarity seems to affect perceived amount of low end sometimes. It all seems to depend on your monitors, subs, room, and positioning. On bass guitar, it's not an issue. If there is a polarity reversal happening, could this be the problem?

[rtcstudio]

Anybody who's not sure about Mixerman's stance on ProTools and digital recording should check out his website. He makes it pretty clear.

I'm surprised he'd be in the same room with a ProTools rig.

He's at www.prosoundweb.com

[Jules]

Could it be a simple DC Offset problem?

That would mess with very low bass wouldn't it?

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Does DC offset occur in analog - digital hook ups? Or just digital - digital hook ups?

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