[sdiy] FETs for distortion

[James Patchell]

One thing you should note about fets is that they have a tendency to "vary" 
a lot from unit to unit.  Depending on the circuit topology, you can pick a 
set of fets that will work perfectly, and if you then replace them with 
randomly selected parts...it will not work the way you expect.  Plus, fet 
parameters drift with temperature in ways that you will definitely 
notice.  By comparison, BJT's are extremely well behaved.  I am not 
suggesting you use BJT's, just letting you know that you are going to be 
tackling.  Most people are pretty used to using BJTs.



At 02:10 AM 12/31/2005 +0000, Seb Francis wrote:
>Hi,
>
>I'm just playing around making a few distortion circuits (to be used for 
>electronic drums + synths, rather than guitars).
>
>I want to try out some distortions with MOSFETs and/or JFETs and I was 
>wondering if anyone had any recommendations of some part numbers to 
>buy.  Preferably they need to be available in UK from Rapid or Farnell, 
>but if there's something particularly good I don't mind hunting around.
>
>I guess I'm asking whether one FET is going to be pretty much the same 
>sound as another (just a case of biasing and driving appropriately), or 
>are there some favourites for this type of app?  Or are there in fact some 
>particular specifications/attributes I should look for when choosing a FET?
>
>I hope this is not too vague a question ;)
>
>Seb
>
>

         -Jim
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