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Old 9th March 2007, 12:07 PM   #61
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So far, I haven't seen anyone recommending substitutes for the JFETs; any suggestions, considering the scarcity of JFETs all around?

Any ideas on cascoding lower voltage devices which will also reduce the input capacitance seen by the preamp?
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Old 9th March 2007, 01:19 PM   #62
AD is offline AD
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Earlier in this thread it was mentioned that the equivalents to the input JFETs are 2SJ74 and 2SK170, which I checked in my Toshiba databook to be true.

To the contrary of many people who complain these cannot be found, there are at least a few suppliers selling these.

This supplier sells them in small quantities and reasonalble prices:
http://www.tech-diy.com/smallsignal.htm

They also have low international shipping charge and accept Paypal.
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Old 9th March 2007, 02:14 PM   #63
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Thanks for the tip AD!

They had everything I needed and the checkout was painless.
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Old 9th March 2007, 03:50 PM   #64
steenoe is offline steenoe  Denmark
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Isnt that one of the DIYaudio users business? Not that I would mind at all If they can supply, be my guest

Steen
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Old 9th March 2007, 04:01 PM   #65
EUVL is offline EUVL  Europe
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Those in Europe could also try www.schuro.de
About the same price, if you include custom charges.

Patrick
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Old 9th March 2007, 04:15 PM   #66
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Quote:
Originally posted by steenoe
Isnt that one of the DIYaudio users business? Not that I would mind at all If they can supply, be my guest

Steen
I wasn't aware. I have no idea who that would be as I see no name attached anywhere, not on the paypal email either. No matter
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Old 9th March 2007, 04:20 PM   #67
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Send a message via Yahoo to jacco vermeulen
New Jersey Jack aka JackinNJ
You know, the guy with the dress.
What did i win this time on jeopardy ?
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Old 9th March 2007, 04:36 PM   #68
RKH is offline RKH  United States
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Default The Company Store

I'm not endorsing and have no financial connection to... simply clarifying and relating past experience...

tech-diy.com is jackinnj on this forum. I've always had great service on the few orders I've placed with him.

Hope that helps.

Ryan
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Old 10th March 2007, 03:39 AM   #69
BDP is offline BDP  United States
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Default Idss

What Idss range should we be looking for? Or should the current be a certain amount through the JFETS, then source resistors adjusted. Does the Idss even make a difference when used as a follower?. With a range of Idss JFETS the current could run from about 2 to 8 ma with 22 ohm source resistors. (If I read the data sheet correctly).

Would'nt it be nice to have all those resources, time, measurement equipment, Oh and talent.

Thanks Nelson for another way to use amplifiers.

BDP
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Old 10th March 2007, 03:51 AM   #70
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The choices for the JFETs is pretty flexible, as are the decisions
about the Source resistance. Clearly you want to have a
voltage rating comparable to the supplies (in this case about 40V)
and the self-bias current should be set with an eye on the
maximum dissipation.

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