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Old 25th March 2011, 10:57 PM   #21
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Quote:
Originally Posted by john curl View Post
The JC-3 does NOT use an AD797.
Hi John,

Thanks for clearing that up. What op amp do you use?

Can you say a few words about the architecture without spilling too many beans?

In MC mode, how many op amps are in the signal path?

In MM mode, what does the cartridge look into? A BJT op amp? A FET op amp? A discrete FET buffer?

This is a beautiful-looking preamp.

Cheers,
Bob
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Old 25th March 2011, 11:21 PM   #22
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It doesn't matter. Besides, I forgot.
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Old 26th March 2011, 12:28 AM   #23
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Originally Posted by john curl View Post
It doesn't matter. Besides, I forgot.
C,mon, John, it does matter, and I doubt you forgot what op amp you used. If you'd rather not say, why don't you just say so?

Its a really nice preamp and we'd just like a peek under the hood.

Cheers,
Bob
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Old 26th March 2011, 01:45 AM   #24
jam is offline jam  United States
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Default Deja Vu

Looks like Mr.Curl is in rare form today...........

Mr.Curl it does matter to some of us ...........but what if the situations were reversed? How would you feel then?

Does it matter or would you have to get real ?


Regards,

Jam

Last edited by jam; 26th March 2011 at 02:07 AM.
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Old 26th March 2011, 02:29 AM   #25
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I forgot.
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Old 26th March 2011, 01:49 PM   #26
kamis is offline kamis  Serbia
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Quote:
Originally Posted by Bob Cordell View Post
Hi John,

Thanks for clearing that up. What op amp do you use?

Can you say a few words about the architecture without spilling too many beans?

In MC mode, how many op amps are in the signal path?

In MM mode, what does the cartridge look into? A BJT op amp? A FET op amp? A discrete FET buffer?

This is a beautiful-looking preamp.

Cheers,
Bob
I got a wrong information in a Internet JC3 review. But John Curl has already described topology of that phono preamp. It could be described as Vendetta with op-amps. First stage linear gain low noise IC , then passive HF eq. Second stage is feedback LF eq. First stage op-amp could be some of low noise J-fet input, like AD 745.
Only mistery for me in power supply is common mode choke value. I know it is horizontal Panasonic choke . Mr. Curl has right not to tell us design secrets of this brand new commercial preamp . It has probably his contract obligations.
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Old 26th March 2011, 02:38 PM   #27
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Quote:
Originally Posted by kamis View Post
I got a wrong information in a Internet JC3 review. But John Curl has already described topology of that phono preamp. It could be described as Vendetta with op-amps. First stage linear gain low noise IC , then passive HF eq. Second stage is feedback LF eq. First stage op-amp could be some of low noise J-fet input, like AD 745.
Only mistery for me in power supply is common mode choke value. I know it is horizontal Panasonic choke . Mr. Curl has right not to tell us design secrets of this brand new commercial preamp . It has probably his contract obligations.
Hi Kamis,

Thanks for this info.

You're absolutely right about John having a right not to tell us anything he considers proprietary, and he very well may have contractual obligations to keep quiet about certain things. However, I don't think it is right for John to BS us with statements like "it doesn't matter" or "I don't remember". That is simply rude. The courteous response is to tell it like it is, and tell the truth. Something like "I'd rather not say" or anything of the like. We also need to recognize that John is a gifted designer who was probably under a lot of cost pressure, and may not be that proud of this particular design, and may therefore not want to get into a conversation about it where a bunch of guys may second-guess him, not taking into account the business realities he has to design with.

Cheers,
Bob
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Old 26th March 2011, 02:54 PM   #28
6L6 is offline 6L6  United States
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Quote:
Originally Posted by Bob Cordell View Post
However, I don't think it is right for John to BS us with statements like "it doesn't matter" or "I don't remember". That is simply rude.

Under the circumstances, I think Mr. Curl is being very polite, considering what he could say.

The tone of a statement is extremely hard to convey in a web forum. My guess is if he were speaking those words to you, you might not hear what you have read.

The real question concerning politeness is actually this - is it proper to pump a professional designer for info (on an open web forum, no less...) on a retail product that is brand-spankin-new??? And then taking offense when he declines?? Seriously??

Last edited by 6L6; 26th March 2011 at 02:58 PM.
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Old 26th March 2011, 03:01 PM   #29
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I am NOT BS'ing you on the FACT that I don't remember. I have to ask my boss what we finally selected of 2 other selections besides the AD797. Also, it is really nobody's business, IF I don't tell you anyway.
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Old 26th March 2011, 03:14 PM   #30
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Thank you, 6L6. You were very kind in your input. As I cannot remember which one we finally selected after listening tests (what a concept, sonic differences in similar IC designs) we selected one that was cheaper and sounded just as good as the AD797, which was our initial choice. It had other smaller advantages, as well.
Second, however, I did not want to get into a 'dogfight' over the choices that I made for THIS design which, in truth does not make it as UNIVERSAL in its application as it would be IF IC's were more ideal. However, they are what they are, and this design will work well with most phono cartridges available today in the cost range that they should be, such as around $1000 (the cost of the cartridge that I evaluated it with) or less, even though it will work just fine with some more expensive cartridges.
However, it is just too noisy to work with my newest cartridge (for me) the Lyra Helicon SL with its LOW output, or an old ADC like Soundminded likes to use, because the inductance is just too high, and bias current just might effect this cartridge. Who knows?
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