Ed,
would you mind posting a link, to see what I have said exactly?
Thank you, Pavel
It was the AD524 an instrumentation amp not at all intended for audio. The AD825 is used by several folks here, the datasheet will invariably just be the dominant 2nd's and 3rd's since they are almost all that matters for SFDR.
BTW speak for yourself about not understanding the subject.
Nope, you brought the elephant in and pretended not to notice it. And you were quite successful- with all the talk about "masking" and "noise," no-one seemed to notice the fundamental problem, despite lots of hints.
Ah, well, I hope you had fun with it.
If I may be so bold as to interject something audio-related: Part 3 of Bruno's 'The G-Word...' article just appeared: The G word: How to get your audio off the ground (Part 3) | EDN
One more part to go.
jan
One more part to go.
jan
Regarding AD524, it is not intended for audio use. Yes I did say that. Scott has said it as well several times. Just look at the complete set of its parameters. I would repeat, that SR is only 5V/us, for example. As John has always claimed the need for high SR, I can hardly understand how 5V/us is enough suddenly.
We should keep at least an impression of a scientific debate, Ed.
We should keep at least an impression of a scientific debate, Ed.
The AD524 is a good 'first start' and the only op amp that I have set up at the moment. 5V/us is the minimum slew rate for preamps. 50V/us is the standard for POWER AMPS.
My question would be for John is he only looking at that IC to learn what he can do with his new test equipment or was he intending to use that device for some unknown audio application? If it was for learning how to use his new equipment what would it matter what IC you are looking at? If for audio I would think that Scott and Pavel must have a valid point about that particular IC.
Right you are, Kindhornman. The AD524 is NOT a uA741, and it is 10 times faster, and 10dB quieter. Not the most extreme set of specs., but typical of most IC's actually used in mid-fi.
It is NOT an op-amp it is a DC precision instrumentation amplifier with specific application constraints. Before someone else finds it Walt and I did an AD624 phono front end (Walt likes doing audio apps), it sounded OK for 1982. Grado 15$ cart and Pioneer TT, no pretensions to hi-end. It was split EQ with 744 as output IIRC. We didn't show it but you can drop an external pnp onto a 744 via the output and comp pins makes it quite nice and it has a lot more slew rate in the first place. At 4nV the AD624 was decent for MM, MI not SOTA.
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Hi end is NOT the only product group that is designed today. There does not appear to be anything really 'wrong' with the AD524, any more than most other op amps.
I didn't think it was a debate! My point was J.C. is starting with stuff he has on hand and is easy to measure what he wants to look at.
BTW Scott gave J.C. the samples!
However Pavel I am pretty sure you understand the issue of current source capability required to drive the impedances required for low noise. After all you seem to regularly use a buffer to drive things.
One thing to keep in mind is Pavel is located where there are lot of external EMI sources while Dick has found amazing amounts of internal noise sources.
(Internal meaning in your residence.)
Talk about NOS! I still find it hard to believe JC does not have a single IC op-amp in his lab. I have 1000's 😀
I don't have a test socket at the moment, I hard wired the AD524, over 10 years ago. This is why I am using it first. Beats a 741, that's for sure.
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