HD I/O - HD Omni Impedance numbers

[BScout]

Does anyone know the output impedance for the +4 output of the DA for the HD Omni? I'm assuming the HD I/O and HD Omni would have the same number. I can only find info on the 192 in a search on the Avid website (which has an output impedance of 50 Ohm.)

Wondering if it is the same.

[albee1952]

Its a fair question, but begs one more; why does it matter(are you having a problem)? I did look at the manual and Avid seems to have left that spec out(in case anyone bugs you about reading it) FWIW, it would be a surprise if it(and the HD IO) are of the same spec due to the nature of circuit design/construction(electronically balanced with no transformers)...

[Darryl Ramm]

I was also thinking the same thing. Why are you worried about this?

And if it’s important you can just measure it. Low frequency sine wave signal gen into a good digital voltmeter or oscilloscope (at high input impedance) measured open circuit and then into one or more load resistors. Solve for the unknown source impedance... lots of books or online resources give the details.


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[BScout]

Not worried. Curious. The question arose due to a comparison of audio output from the Omni vs the output of the MTRX/DAD AX32; the difference in sound quality due to the ratio of output to input impedance of a known speaker (outside of the known converter differences.)

As for the HD Omni vs the HD I/O, the analogue outs are supposed to be exactly the same. Zero difference. Parts moved from one to the other.

Yes I can measure it (though a bit of a hassle to get behind the rack and disconnecting breakout cables) but since Avid supplied 192 numbers (eventually) and also left those out of the normal listed specs, asking here to see if Avid could/had those numbers for the HD I/O or Omni seemed less time-consuming.

[Darryl Ramm]

Huh? None of these outputs are driving a speaker... they are driving amps, which if solid state will typically have tens of thousands of ohms input impedance... and because of that exact output impedance really does not matter, what matters is output level.


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[BScout]

Yes. An amp on an active speaker with orders of magnitude input impedance greater than the output impedance of the audio interface. Yes, output level is easy to match.

Still not an answer to my question of the output impedance of Avid's audio interfaces (including OEM ones from DAD) and if they match. There would have a been a design goal for Avid's internal products. If the 192, HD I/O, and Omni were designed for 50 Ohm and the MTRX/DAD was designed to 300 Ohm, I'd like to know that.

[Darryl Ramm]

But again, why does it matter? It’s likely just not speced because nobody cares... because it makes no difference to any real world use.


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[Rich Breen]

Originally Posted by Darryl Ramm

But again, why does it matter? It’s likely just not speced because nobody cares... because it makes no difference to any real world use....

I dunno - I think it's a perfectly legit question - some of us *do* indeed care about such things. Granted, in *most* cases it's just not gonna make a difference, but there's still plenty of real-world instances where you're driving 250 feet of crappy plenum cable, or old transformer inputs or gear from the 50's where load impedances are very low and/or finicky, and source impedance could be a factor in different gear sounding different.

In the OP's case, hard to tell if it could really be the reason for differences in sound driving a modern set of active monitors, but does seem very unlikely - that said, I've seen stranger things...

Source impedances should indeed be part of a complete spec sheet on any piece of professional audio gear - their omission is just part of the general sloppiness in documentation for most pro gear.

All of that said, the differences in 'sound' between two devices driving the same load are unlikely to be revealed in the single "impedance" number usually quoted in a spec sheet; more often comes down to the exact nature of that source/load impedance; how reactive it is - is it capacitive or inductive in nature, etc, etc. Nonetheless, the source impedance spec can be useful in diagnosing/foreseeing interface issues.

[YYR123]

Originally Posted by Rich Breen

Source impedances should indeed be part of a complete spec sheet on any piece of professional audio gear

This is true, and this is what I was gathering.....using your outputs to drive external gear will change the sound based on the impedance.

It may be the same as other gear but it would be nice to know it.

[SergUS]

Hello!
Tell me what is Avid 16x16 analog and HD OMNI with HD Native Thunderbolt. If you feed a rectangular signal from any output to any input at a sampling frequency of 44100 or 48000, will you still have the signal without visible changes or be distorted? If I switch to 96000, the signal remains almost unchanged!
I tried to do these manipulations with I / O 192 and this interface produces almost ideal rectangle shapes at any sampling frequencies. If from the output of Avid 16x16 analog to apply to the input of 192 I / O then the result is also excellent. If on the contrary, the result is depressing, which indicates the problems of the input channels at 16x16. the same problem with Avid Omni. I'm curious about this on all new avid interfaces?