Some 8 years ago I had a serious project with a retired IC designer to get a couple of AD844 bare dies, interconnected in a smart way, packaged in a 20-pin DIL.
Total bill was supposed to be some 12k$ for few 1000 chips.
Backed out at the last instant because, no matter how good it would be, it would still be shot down if someone would thoughtlessly use the word 'IC' somewhere
"I'm following this thread with interest".
jan
A beautifully done high gain circuit..... with elegance and simplicity.
[ BTW -- th jfets are still available on internet. At least 6 months ago when i bought some]
high vs low gnfb excercise -
You missed a few theads leading up to this --> Actually, it is also about discrete low gnfb vs. IC or high gnfb. Most IC are high gain circuits which depends on high nfb for low distortion. In some audio circles high gnfb has been out of favor for many years. Scott's discrete but high gain design is to be compared and listened to IC and other circuits.
-RNM
You missed a few theads leading up to this --> Actually, it is also about discrete low gnfb vs. IC or high gnfb. Most IC are high gain circuits which depends on high nfb for low distortion. In some audio circles high gnfb has been out of favor for many years. Scott's discrete but high gain design is to be compared and listened to IC and other circuits.
-RNM
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John, no need for simulation. Use your common sense. It is trivial. I can understand if such solution was proposed as basic block for some digital device, but not for analog amp, especially when we speak about high end.
EVUL suggested we stick with cheap readily available parts. I think I could certainly drive 100 Ohms at 20V p-p and still be under 110dB seconds at 20kHz.
BTW that other circuit is free of seconds either.
Yes I forgot to mention the circuit can be easily tuned with loading or degeneration for a large range of gnfb. As first presented it is as Wavebourn notices very much in the op-amp vein, very large Aol and very low frequency breakpoint. You'll have to leave me out of the listening though I tend not to hear any differences until they're gross.
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Brad, sorry I should have said "that I had not seen elsewhere...". Doesn't mean that this stuff was not out there, just that sitting in relative isolation, I had not found it via various pseudo random efforts to locate this sort of information - this was before the internet as we know it today... that meant trips to various university libraries and bookstores - many of the texts were even back then in the >$100 range, which was daunting. I persuaded someone to make me a photocopy of Grebene, because I couldn't swing the bux for even a used copy... whaaaaa!
_-_-bear
I know the feeling. Some out-of-print texts and monographs are holding their value extremely well. That Grebene you mentioned is available as shown in the reissue Classics series, but isn't cheap --- and it's softcover!
Just checked bookfinder.com for Ed Cherry's Amplifying Devices and Low-pass Amplifier Design, a generally reliable book and one with a unified treatment of hollow-state and sand-state, from 1968. A somewhat beaten-up ex-library copy is offered for nearly $200, while a Canadian seller helpfully offers one for a mere ~3500. Of course it can hardly cover everything, and much of it is very dated, but fundamentals are pretty much timeless. They will pry my copy from my cold dead hands
Tricks of the trade?
Thank you. Are there any degeneration tricks that you would be allowed to show/teach?
Thank you. Are there any degeneration tricks that you would be allowed to show/teach?
As I proposed before, close local feedback before the buffer. If you want to keep high DC gain for better output zero control at the buffer's output when global feedback is closed, use series R-C for this local feedback path.
The one I was thinking of is well known (Bernie Oliver?), just the right drop on the emitter degeneration resistors (output devices) will do some first order distortion cancellation. I don't remember the exact numbers.
I think there is still some NOS on 194 but the word on the street is that you can do as well with existing monolithic duals for about every parameter (the MAT series?).
Don't know about the 2210.
Also not to be forgotten is THAT's arrays, (EDIT: just noticed SW's post crossed in cyberspace) which have emphasized log conformance. I wish they could do something with higher beta though. I spoke to them about this and was told that they had played around with attempts in that direction, to find that breakdown voltages were all over the map.
I wish I could afford to fund some duals based around the BF862.
The obsolete parts problem reminds me of the story about the Arnoux Associates design for Infinity (the Harman company) of a switchmode power amp for automotive aftermarket. The product was announced about three years running at Winter CES, and then never shipped until after that. The late Mack Turner was the designer, and he swore that the only comparator that worked for the pulse-width modulator was a part that had been discontinued by TI. Steve Dove and I joked about this a bit, perhaps somewhat naively, but Infinity took the admonition seriously, and with the financial resources available then, commissioned a run of devices. I think the tab was over 100k
The saddest part of the story was that when the amp was finally shipping, it was somewhat expensive for the output power, and the market, consisting mostly of "kids" pimping out their vehicles, was almost nonexistent: the thing didn't look like it could do serious power, no big heatsinks etc. I heard that there was a final attempt to sell it by simply putting it in a larger chassis!
Still no dice.As I've said before, You can't make this stuff up --- no one will believe you.
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John is my hero.
Love this one :
http://www.diyaudio.com/forums/anal...discrete-opamp-open-design-4.html#post3138300
and this one :
http://www.diyaudio.com/forums/anal...discrete-opamp-open-design-4.html#post3138366
But stupid question, where to put the -Vin on the second one ?
Patrick
Love this one :
http://www.diyaudio.com/forums/anal...discrete-opamp-open-design-4.html#post3138300
and this one :
http://www.diyaudio.com/forums/anal...discrete-opamp-open-design-4.html#post3138366
But stupid question, where to put the -Vin on the second one ?
Patrick
The saddest part of the story was that when the amp was finally shipping, it was somewhat expensive for the output power, and the market, consisting mostly of "kids" pimping out their vehicles, was almost nonexistent: the thing didn't look like it could do serious power, no big heatsinks etc. I heard that there was a final attempt to sell it by simply putting it in a larger chassis!
I am going to try today in the field Behringer 2x300W per channel amp, class D with SMPS. I paid $185 for it including shipment. No heatsinks (almost), just a fan.
