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What is wrong with op-amps?
What is wrong with op-amps?
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Old 9th January 2017, 01:27 AM   #4621
john curl is offline john curl  United States
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Another analog designer that I really respect is Sid Smith. I only met him once over dinner, but I am sorry that I did not know him better. It was his Marantz 9 in triode, his earlier 50's triode design that I directly compared my first solid state design efforts (and failed) and even now, the circuits that he did for the Marantz 10 (that I am listening to now) that kept me struggling to make better and better audio circuits. Through a process of elimination, did I find what was different between his designs and mine. Also, I have some of those German EL34's that he liked in some Dyna MK 4's that I keep around for reference.
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Old 9th January 2017, 08:58 AM   #4622
nigel pearson is offline nigel pearson  United Kingdom
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Originally Posted by billshurv View Post
Well firstly DeForest was one of his first names, and although named in honor of Lee de Forest there is no relationship.

Secondly 'Spook'. Come on Nigel...:P
That's called in a rush to do what I should be doing. Dyslexia seems common in engineering. If you look up the good doctor he is named after him and some say related.

https://en.wikipedia.org/wiki/DeForest_Kelley
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Old 9th January 2017, 09:12 AM   #4623
nigel pearson is offline nigel pearson  United Kingdom
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Originally Posted by john curl View Post
Another analog designer that I really respect is Sid Smith. I only met him once over dinner, but I am sorry that I did not know him better. It was his Marantz 9 in triode, his earlier 50's triode design that I directly compared my first solid state design efforts (and failed) and even now, the circuits that he did for the Marantz 10 (that I am listening to now) that kept me struggling to make better and better audio circuits. Through a process of elimination, did I find what was different between his designs and mine. Also, I have some of those German EL34's that he liked in some Dyna MK 4's that I keep around for reference.
Sid's hi fi was Model 9 in triode ( g2 to anode ). Floating LM317 at circa 450V regulator ( he was very insistant to let that be known ). Thorens TD160 with Grado PU ( Joe was his friend ). And Song Discman as battery PSU was a big deal to Sid. Speakers were Quad ESL 63 with no covers. In terms of total system distortion it is the lowest I had ever heard by a very long way. I remember Sid saying as he had no idea on my views that he had recently been asked to change capacitors in a Model 9 and to his total surprise could hear a difference. The best bit was " Nigel, you have to believe this ". The most stupid thing I never asked Sid was if he knew Albert Einstein. They were more or less neighbours if I'm right. It seems totally unlikely he didn't. Sid told me he wasn't that gifted except he never gave up. History knows that to be the real gift. He also said between he and Dick Sequerra you got one decent engineer.
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Old 9th January 2017, 09:51 AM   #4624
nigel pearson is offline nigel pearson  United Kingdom
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Something else. When Marantz made some generic Model (?) Ken Isiwata never bothered to contact Sid. Sid said he would have been glad to help and wouldn't have wanted money. With Sid it would be very easy to mistake him for a hobbiest as he was so modest about anything he talkled about. As I was taught " You never know who you are talking to ". That has been part of my learning. My three next door neighbours knew very well, Margret Thatcher, Stephen King ( I was said to be as bad as him except I sure knew my Bible, the neighbour was a Bible basher and I retain factoids ). More importantly Roy Rogers plus 4 legged friends. That was because I asked.

Sid to me. " Nigel, I hope one day my transistor designs become respected. I suspect all they need is capacitor upgrades. Problem is we were taught it couldn't matter and I saw no reason to question that". He lookd very sad to think he wasn't noted for them. You could see it in his eyes. Please note the " I saw no reason to question that ". How many here like the fact that no one asks them to question things ? Know things? Yes. Question things ? I think our Royal Society says " Take no one's word for it ".

Do video op amps work in all active phono stages? Nothing seems to say they wouldn't ( noise perhaps and you need to read the graphs more than usual ). The low output voltages assume a second stage. 75 uS with gain followed by 3180/318 with lets say NE5534 or better. Some work at 32 V so could be the second stage. All inverting if MC ( twice inverting ideally ). My Lyra PU will cope nicely when 22R input loading. It seems just as happy with 47K! It's designer is a DIY member.

Again late to do some plumbling for a friend who's moving house so do the correctons please.
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Old 9th January 2017, 10:32 AM   #4625
Bonsai is offline Bonsai  Europe
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Originally Posted by john curl View Post
Nigel, I think that a decent tube phono stage vs a single op amp 'equivalent' makes a poor comparison. The tube phono stage will have more peak output swing, and the op amp will suffer heavy loading at high frequencies.
A better comparison is a 2 op amp design, where the EQ is either split or stuck in-between two op amps. This appears to work much better. Still, the tube phono stage can sound better most of the time. PS I miss Michael Gerzon too!
You can easily buffer the opamp (also make the whole thing class A if you want) and end up with superb noise performance and >30 dB overload. If you want >80 dB with a cart connected, use some JFET's in front of it. See Syn08's website on how to do it.

We are just having a discussion about phono stages over on the Source forum. While I don't decry your many highly rated designs and awards in this area, you can't go making blanket statements like the one above re opamp designs. They are simply not true. Splitting an EQ stage for any reason when using opamps is suboptimal - noise, overload and distortion. For tubes - agree - you have the voltage swing, but loading effects mean you have to use high EQ values (transformer impedance matching may be a way out here, but that's added complexity and cost). And, I have yet to read about or see a test report where a tube phono stage bests the best solid state can offer.

Separately, EAR had a phono stage where Tim dP proudly spoke about it having '42 tubes'. The mind boggles.
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Old 9th January 2017, 10:46 AM   #4626
billshurv is online now billshurv  United Kingdom
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What is wrong with op-amps?
Ah the EAR 'Professional 42' (or was it 52?). Very little info about that around.
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Old 9th January 2017, 11:31 AM   #4627
DF96 is offline DF96  England
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Originally Posted by Max Headroom
I mean higher order IMD products that are phase (time) shifted wrt lower frequency fundamentals due to change in junction capacitance as you state.
Don't confuse phase shifting with time shifting. They are not the same thing.
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Old 9th January 2017, 03:45 PM   #4628
Bonsai is offline Bonsai  Europe
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Originally Posted by billshurv View Post
Ah the EAR 'Professional 42' (or was it 52?). Very little info about that around.
Maybe they only made one?
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Old 9th January 2017, 05:46 PM   #4629
jfetter is offline jfetter  Costa Rica
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What is wrong with op-amps?
Sorry I could not hold back, the devil made me do it.

-bruce

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Old 9th January 2017, 06:23 PM   #4630
john curl is offline john curl  United States
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If ONLY, .00003% measured Thd always meant low subjective impression. '-)
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