John Curl's Blowtorch preamplifier part III

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#14,321
Jack Bybee is now 89 years old. He got his masters in physics from UCB around 1956. He went to work on classified military projects soon after.
When he was working in Southern California for some unnamed company, he was assigned to help Richard Feynman at Cal Tech get caught up on the latest superconducting info.
Years ago Jack told me of how extra smart Feynman was, not like the rest of us and how he had a rivalry with Gell-Mann just down the hall. They used to insult each other I think. It was only a small part in Jack Bybee's adventures when he was much younger.
 
#14,327
EUVL, I am pleased that my early attempt to make a quality OP-AMP gave you something to try. Of course, this design is 46 years old, and parts have changed, yet the basic topology still is useful. I designed this OP-AMP for Mark Levinson in 1973, as the phono stage for the Levinson JC-2 preamp. I don't make phono stages in this way, anymore, so I don't build this OP-AMP very often, either. It was very quiet for the time, about 2nV/rt Hz or better, with switching jfets that at the time were as quiet as anything in the industry. Later, they changed the processing, and the later parts are now useless for input stages. Also, the E212 has been replaced by the J113 to complement the J175 with all 4 devices matched for Idss. This design emphasized low noise, high(ish) open loop bandwidth and good gain bandwidth, all operating Class A throughout.
 
#14,330
scott wurcer said:
Far more likely as someone put it "diva jewelry" for the wannabe's. They make no claims for anything but appearance factor.
Click to expand...

Pro use is as the input connector for an on-stage microphone. Besides the glitz it makes identifying the lead singer's microphone easy.

Now as to how the crystal energy sharpens the focus of the acoustical energy into the microphone's electrical signal is a mystical process best only known to a few truly skilled practitioners.

Of course special microphone cable must also be used so as not to degrade the vocals.
 
#14,333
john curl said:
EUVL, I am pleased that my early attempt to make a quality OP-AMP gave you something to try......
Click to expand...

For your interest :
This SMD version uses Toshiba SMD dual devices throughout.
Input noise is 2.5nV/sqrtHz.
Current assumption is 11mA, operating in pure class A.
Open loop bandwidth is 300Hz at -3dB. Open loop gain is 85dB.
Phase margin at unity gain is 70°.

It is on its way to a friend who has an AP2722 for distortion measurement.


Regards,
Patrick
 
#14,335
EUVL, for the record, you changed several of the operating parameters from the original design. I suspect that you increased the value of the input stage load resistors, and that will lower the open loop bandwidth to, what you say, is 300Hz. I used only 100 ohm load resistors and I had 15ma in each input device, so my total current was 60 or more ma, rather than 11 ma that you cite. Still, you have a very practical OP-AMP that should sound pretty darn good.
 
#14,337
I am aware of the changes and hence never claimed that it was a JC2, but only following the topology.
I have to lower the input and 2nd stage bias current because of limited dissipation of the SMD devices (~50mW per device).
Also, intended as replacement for DIP8 or SOIC8 devices, total current consumption of 60mA might prove problematic.
I am aware of the penalties in open loop bandwidth and also slew rate.
But it is a design compromise that I have chosen to take, considering the other requirements.

Simulations suggest very good performance nevertheless.
We'll know more in a few weeks.


Patrick
 
#14,338
“l toured China for 10 days with one of these guys. Said he was a black ops agent at the Bay of Pigs, then spent 3yrs recuperating in a secret hospital in Mexico... it only got better. “

You come across them in all walks of life. I was in Cambodia with my wife visiting friends a few years ago and they had some other visitors turn up on one of the days. One of the guys (happened to be a Londoner) was out there because he’d found some ‘cure’ for Autism in water from Cambodia. I’m sure my bs antennae must have come right out of the top of my head after he’d been going for a few minutes. Thing is, he was taking this stuff back home and selling it to people.

He invited us to his holiday home in the Bahamas. Naturally we never took the offer up.
 
#14,339
“Years ago Jack told me of how extra smart Feynman was, not like the rest of us and how he had a rivalry with Gell-Mann just down the hall. They used to insult each other I think.”

I watched an interview on TV or YouTube with Gel-Mann. He was explaining some really complicated physics concept - naturally I was totally lost - when suddenly his voice trailed off and he looked a bit confused, frowning, and said ‘I forgot what I was going to say . . . “

Hilarious.
 
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