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rme adi-8 qs op-amps [photos]
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1954U1
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#1
29th July 2008
Old 29th July 2008
  #1
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rme adi-8 qs op-amps [photos]

I've broken the warranty of my RME adi-8 QS and opened it, was curious to look at the op-amps,
after reading on the manual:
"While the analog limiter is constantly within the signal path, it operates
fully transparent as there is no control signal generated".


jrc 4580, at least [not bad..] 2 for each A/D ch and 2 for each D/A ch:




jrc 2043 [part of the analog limiter, I think], 2 for each A/D channel:




So now I have an issue..
why on the hell should I need lot of features, when the analog I/O paths of my converters are probably
worse than all of my analog sources, pres, mics, outboards?

And I dont think that it would applies only to rme adi-8 qs.

What should people do, to have great analog paths in a setup of say 16 A/D D/A chs converters?
Go with radar ada?
Buy a pile of UA 2192?
Ebaying for some old 44-48k converters with great analog components?

Or am I wrong, and the cheap op-amps are doing nothing harmful to the audio signals,
because it matters only the circuitry design?

[and they're not socketed, too.. damn smd]
#2
29th July 2008
Old 29th July 2008
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I think you should judge a circuit on how it sounds, not on what hideous malignancies were done to get it that way.

(I have never heard the new QS converters)

But I do think saying you can't open a chassis up without breaking the warranty is obnoxious on RME's part... tutt
1954U1
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29th July 2008
Old 29th July 2008
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"Warranty break" or something similar was written on a screw's label, so I'm assuming I've broken it..
[cant resist at bans]

About the sound of the QS, I'm trying to not go in the subjective field..
My goal was to put a general question, not RME-specific related, about the analog paths in converters.
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29th July 2008
Old 29th July 2008
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I've not seen the new model, but the older one used M-Dacs to adjust gain, it was a dirty solution. Those Japanese opamps won't win any awards, they are surface mount so they would need de-soldering for replacement. A set of National LME49722 opamps would be an ideal replacement as they are the cleanest opamps made with THD below -155 db, very quiet (1.9 nv/hz/sq) and precision so they have little input bias current and virtually no output offset voltage.

Jim Williams
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29th July 2008
Old 29th July 2008
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I´m a bit surprised by the obeservation, that low-quality opamps are said to be used in rme-products and keep thinking of doing a mod to my rme adi8-ds (or at least one to hear the difference).
Mr. Williams, so do you think changing the opamp to a National LME49722 would change the actual sound or more the s/n-ratio in a favorable way?

A quick googling didn´t show me any dealers with national opamps in germany, any alternatives?

Thanks

bojan_1
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29th July 2008
Old 29th July 2008
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This is a new part, not yet into distribution. I bought mine directly from National Semi. These will open up the sound and reduce input noise, but they are still much less noise than the converter chip. They will not recover what is lost in their gain adjustment designs, but still should offer an improvement if you are inclined to do some surface mount re-work.

Jim Williams
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1954U1
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29th July 2008
Old 29th July 2008
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Quote:
Originally Posted by Jim Williams View Post
I've not seen the new model, but the older one used M-Dacs to adjust gain, it was a dirty solution.
Thanks a lot for all the info!

Is there a way I can find if MDACs are actually used to adjust gain in my adi8-QS, just by watching at the board?
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29th July 2008
Old 29th July 2008
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If you know your way around in this stuff, you should be able to observe gain changes on a scope. Part numbers with a Google search can also tell you what the part is and perhaps what it's doing.

Jim Williams
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