John Curl's Blowtorch preamplifier part II

[Joachim Gerhard]

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.

[john curl]

I have 100 ea. They were as good as advertised.

[Joachim Gerhard]

I believe that. I will do my own measurements. The jig is ready.

[scott wurcer]

Originally Posted by jneutron

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.

[Steve Eddy]

Originally Posted by scott wurcer

You can tell I never use the things.

Yes.

Pity.

se

[hitsware]

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.

[john curl]

Hitsware, mosfets are very, very, noisy. Big time noisy, except at RF.

[Joachim Gerhard]

Here is the circuit i mentioned.

[Joshua_G]

Originally Posted by john curl

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?

[hitsware]

Originally Posted by john curl

Hitsware, mosfets are very, very, noisy. Big time noisy, except at RF.

Even with 1000's of them in parallel ?