JFET preamp, battling 1/f noise

[Phil Allison]

"Pooh Bear"

And a device with 1nV / sqrt Hz is essentially noiseless compared to a
guitar
pickup !

** Go tell "elephanthead" that

- he's got a PdD in physics !!


..... beam me up Scotty ......






........ Phil

 

[Ken Smith]

I have a JFET preamp which appears to be measuring in the ballpark of 6
nV/rtHz at higher frequencies, but with a 1/f noise corner around 500
Hz, which seems a bit high. The JFET is a 2N4393. Can anybody offer
some general pointers for avoiding 1/f noise in JFET circuits?

Change to the IF3601 or a LSK170 as the FET.

 

[[email protected]]

"Pooh Bear"



** Go tell "elephanthead" that

- he's got a PdD in physics !!


..... beam me up Scotty ......






....... Phil

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?

 

[John Larkin]

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

 

[Phil Allison]

<[email protected]>

** What is this arrogant cretyn on ???

No, go tell Phil Allison.

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

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

The most charitable thing I can think of
saying is that we both started out making the same mistake,

** No errors came from me at all.

( snip opinionated drivel falsely presented as fact )

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.

** Because that was a correct answer to your *original* question.

As an aside, what data
were you looking at to suggest that the 2N5457 is quieter than the
2N4393?

** 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.

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.

** You are talking absolute rubbish.

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

There is always one guy in the bunch who understands audio.

** Well is is not you and certainly not Win.

Win Hill
showed me how to interpret a noise spectrum in a way that is relevant
to audible performance and believable to a physicist.

** 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 ?? )

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

** 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.

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,

** 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