[sdiy] What makes a transistor "low noise"?

[john mahoney]

I don't know the answer, but I wanted to point something out. First,
you said "noise." Then you said "distort signals." Noise and
distortion are different beasts! Yeah, you knew that.

Now, I've seen "total distortion + noise" in specs because both noise
and distortion result in the output not matching the input. But still,
they are different.

Think of guitar fuzz boxes: some are noiser (hissier, usually) than
others while some distort more than others. More importantly, the
characteristics of the distortion can vary widely. Sometimes you'll
tolerate the hiss because the distortion sound is so good. Happiness
is a warm fuzzbox... :-)

Tubes and transistors distort differently, FETs distort more like
tubes than bipolars, etc. Just for one example, Don Tillman likes the
sound of the J201 for his nifty guitar preamp
(http://www.till.com/articles/GuitarPreamp/index.html). Totally beside
the point of your question, though.
</ramble>
--
john (who's got J201s in his Mouser shopping cart)


----- Original Message ----- 
From: "Metrophage" <c0r3dump23 at yahoo.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Friday, November 05, 2004 11:31 AM
Subject: [sdiy] What makes a transistor "low noise"?


> As I BEGIN to understand how transistors work, I wonder about this.
I
> often see op-amps labelled as being less noisy than general-purpose
> types, but typically not for transistors. Still, I have heard that
some
> are noisier than others.
>
> What is it about transistors which would indicate that they would or
> would not distort signals somehow? How are such factors reflected in
> the specs which are usually offered?
>
> Through my time of synth reading, I feel I have a rough idea of what
> makes some op-amps more or less suitable for a given application.
Not
> yet so with transistors though! I'd be psyched to hear some info and
> opinions on this.
> CJ
>