JFET preamp, battling 1/f noise

Change to the IF3601 or a LSK170 as the FET.

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kensmith@rahul.net   forging knowledge

No, go tell Phil Allison. The most charitable thing I can think of saying is that we both started out making the same mistake, you corrected yourself before I did, then you dropped the ball. The time to ridicule a question is before pleading ignorance about the answer, not after.

I can take my lumps for getting excited about a noise level that is probably irrelevant to my application. But you are the one who jumped in and started suggesting different transistors. As an aside, what data were you looking at to suggest that the 2N5457 is quieter than the

2N4393?

Halfway through a pleasant discussion of transistors, you pointed out that we were talking about a negligible contribution to the NF in my application. I agreed, but said that I wanted to go a bit further for the sake of understanding 1/f noise in general. You sent me to Google, while speculating (see your comment about wagering) about chaos theory and fractals. Ball dropped.

There is always one guy in the bunch who understands audio. Win Hill showed me how to interpret a noise spectrum in a way that is relevant to audible performance and believable to a physicist. That was helpful, and filled a gap in my knowledge.

I only mentioned my education, because it seemed like the discussion was being dumbed down for my sake.

In the OP, I asked specifically about managing 1/f noise in JFET circuits. For all of your bluster, you had nothing intelligent to say about the central issue, and are now beating a dead horse. A lack of technical knowledge is shown in sharper relief against a backdrop of arrogance. Have you considered going into middle management?

Ignore Phil. He has a disorder.

John

** What is this arrogant cretyn on ???

** Grow up, it was a joke - "elephanthead" !!!

Use a damn silly name - expect to get sent up for it.

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** No errors came from me at all.

( snip opinionated drivel falsely presented as fact )

** Because that was a correct answer to your *original* question. ** The descriptions supplied by the makers, for one.

2N4393 = " switching j-fet"

2N5459, 2SK30A = " low noise, audio j-fets "

I use the latter types in one of my published project designs, an active DI box.

As a bass player, I 'm sure you know what that is.

** You are talking absolute rubbish.

Go do the search - there is such a connection with 1/f noise.

** Well is is not you and certainly not Win. ** Subsequent to my pointing out the *exact* same things.

Currently doing a PhD in " re-writing history to suit yourself " too ????

The Nazi Party will likely fund that with glee !!

BTW:

A usenet debate has one beauty - all the words are there to be seen with dates and times supplied.

Only fakes and damn LIARS attempt too circumvent that "beauty" by reposting the debate in the OWN words.

( Remember "usenet" = the thing YOU are not a member of ?? )

** Studying Physics is not the same as learning about electronics. Electronics is an immensely * practical and commercial business* - a branch of engineering with many sub branches and special expertises associated. ** BULLSHIT.

The central issue to obtaining low noise is to use the right sort of j-fet.

Exactly as I pointed out in my initial reply to you.

Only after posting that, did I see your follow up with the schematic.

Having seen that, the issue of noise below 500 Hz seemed not very relevant.

But, YOU did say that your circuit "looks a lot like" the one in the link - which does not say it is the SAME or being used for the same purpose as in the link - ie a Piezo pre-amp.

** A lack of technical knowledge is shown in sharper relief against a backdrop of arrogance. Have you considered going into middle management?

....... Phil