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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 18th March 2011, 04:56 PM   #11501
Joachim Gerhard is offline Joachim Gerhard  Germany
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I had a long discussion with Burkhard Vogel and he told me that the Hitachis are not that good as advertised. He measured an rbb`of 14 Ohm. The lowest rbb`he measured was the Toshiba 2SC3329 with rbb`of 2 Ohm. The second best was the BFW16A, an old stablemate.
It has an rbb`of 4 Ohm at 25mA with hfe of 35. It translates into 0.28nV/qHz. fce is quite high at 250Hz. A circuit was shown in "Ultra-low-noise Preamplifier for MC phono cartridges " Nordholt & van Vierzen, 1980.
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Old 18th March 2011, 05:00 PM   #11502
john curl is offline john curl  United States
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I have 100 ea. They were as good as advertised.
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Old 18th March 2011, 05:51 PM   #11503
Joachim Gerhard is offline Joachim Gerhard  Germany
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I believe that. I will do my own measurements. The jig is ready.
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Old 18th March 2011, 06:02 PM   #11504
scott wurcer is offline scott wurcer  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by jneutron View Post
Actually, no. I'm going by memory...used to play with waffle packs and wafers back in the 80's. So I lived dice..

If anything, it's faulty memory. I found some mat-02 stuff on my drive, I may be confusing the two...



I'm not sure, but I think the 194 and 394 are just different grades of the same die.

But I'n not sure if this is the die I'm thinkin of however..

Cheers, John
I meant the original story, Bob Pease said the part happened when he joked about just paralleling something like LM101 input transistors. Yes National used 1** ,2**, and3** as grades, runs you out of numbers faster.
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Old 18th March 2011, 06:25 PM   #11505
Steve Eddy is offline Steve Eddy  United States
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Quote:
Originally Posted by scott wurcer View Post
You can tell I never use the things.
Yes.

Pity.

se
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Old 18th March 2011, 06:39 PM   #11506
hitsware is offline hitsware
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http://users.ece.gatech.edu/~lanterm...ors/AN-222.pdf

Right ...... 194 and 394 are grades.
Anyways I still surmise power mosfets to
be quiet because they are comprised of
many 'cells' in parallel.
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Old 18th March 2011, 06:44 PM   #11507
john curl is offline john curl  United States
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Hitsware, mosfets are very, very, noisy. Big time noisy, except at RF.
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Old 18th March 2011, 07:03 PM   #11508
Joachim Gerhard is offline Joachim Gerhard  Germany
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Here is the circuit i mentioned.
Attached Images
File Type: jpg Nordhold & Van Vierzen.jpg (96.7 KB, 304 views)
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Old 18th March 2011, 07:36 PM   #11509
Joshua_G is offline Joshua_G  Israel
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Quote:
Originally Posted by john curl View Post
We buffer with a 2N5564 pair used in follower mode.
Sorry, I'm not clear how you buffer the JFETs, are the 2N5564 used as CCS, or cascode, or as source followers?
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Old 18th March 2011, 08:23 PM   #11510
hitsware is offline hitsware
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Quote:
Originally Posted by john curl View Post
Hitsware, mosfets are very, very, noisy. Big time noisy, except at RF.
Even with 1000's of them in parallel ?
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