Is this a trick question? You need to identify the op-amps and define signal correlated noise.
Pick the same op amp for all three. If you optimize op amps you can do better of course, but the issue is topology.
As to noise, does the noise level increase when signal is present? (Pick any real op amp for that question.) What contributes to the increase in noise level?
The AD8099 has a flat input gm and so much BW that the operating point of the input devices changes only minutely so compared with the 1K input (4nV) it would be unmeasurable. In general any increase in noise in internal stages does not get back to the input to any measure. If that's what you are talking about, I'm never sure.
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we could probably list a few 2nd order effects - most not unique to op amps - any transistors, resistors will show some level of noise modulation with signal
bulk metal foil R are "the best" on excess noise, TC - but we've been told they don't "sound the best"
and these 2nd order noise modulation effects can be orders of magnitude less than the Zoo of analog magnetic tape noise artifacts
bulk metal foil R are "the best" on excess noise, TC - but we've been told they don't "sound the best"
and these 2nd order noise modulation effects can be orders of magnitude less than the Zoo of analog magnetic tape noise artifacts
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Thanks, I've ordered a few to play with.
The issue is that in a real circuit there is always noise. Some of it comes from the active components, others from the passive parts and still other comes in from the external connections, such as input and output leads, along with the well know power supply issues.
Which noise source is dominant? What happens when you have two noise sources and a non-linear channel?
With matching inverting gain stages some distortions cancel and the result can be better than predicted by simple feedback assumptions. In the case of uncorrelated noise the math is almost clear.
But in all real amplifiers there may be some bandwidth modulation due to signal and or slew rate limitations. Does this influence the noise? If there is a signal related correlated noise what is the bandwidth of such noise.
Can this noise conjugate with other stage noise to produce correlated artifacts back in the audio band?
At what levels do these issues occur?
Yes signal induced error in the feedback loop is a controllable issue when recognized.
Doesn't that have more to do with Erich Leinsdorf than Sheffield Labs? On the other hand, nothing the Los Angeles Symphony has done has ever excited me.
John
I guess that's all you can expect from a vanity lable. Lyrita had some excellent stuff in their catalog that I enjoyed a lot more. Nonsuch's Geroge Crumb series is still one of my favorites even though groove pre-echo is obvious on several tracks.
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I heard them accompany Abel Gance's Napoleon live. It was pretty exciting.
Heard some LA stuff on the radio last week that I thought was good.
Maybe that was the film.
Look, I don't want to critcize Leinsdorf, maybe once the musicians and the conductor were confronted with the one take through to the end nature of the process it affected the result. The lable is clearly more interested in their sonic "thing".
In the context of making a recording I don't know. I have seen stories of several takes being spliced together for the best parts of each. We are possibly over thinking this issue, what's there is there nontheless.
Shouldn't the + Input see approx. the same impedance as the - Input, in case of a bipolar Op Amp?
Makes you wonder why there are so few "live" orchestral recordings.
It's not that it's daunting, it's that a recording is an archival document, not a one-off performance. Add in the strict admonition to hit exactly the volumes you did at the run-through, NEVER exceeding them by even a little and what you have is a safe, sterile, performance, professionally executed, but taking no chances and not "going" with the feeling. Multiply that times 100 (or so) musicians. Just curious, have there ever been any D2D orchestral performances that were exciting? Within the genres I favor, I can't think of any jazz D2Ds that I'd listen to more than once.
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