TB303 vco pt2

[Heiko van der Linden]

I used 2n3819 it works fine and is generally available.

Arthur Harrison wrote:

> Another good N-ch. JFET is the 2N5484, with a Vg-s(off) of 3v max.
> And, it's very inexpensive and generally available.
>
> Art
>
> -----Original Message-----
> From: jhaible <jhaible at metronet.de>
> To: Tony Allgood <oakley at techrepairs.freeserve.co.uk>; synth diy
> <synth-diy at mailhost.bpa.nl>
> Date: Wednesday, November 18, 1998 6:01 PM
> Subject: Re: TB303 vco pt2
>
> >> some time. However, once I put the FET in, differences were evident. I
> >> used a BF244 and then a 2N3819. Both n-type JFETs. Firstly, the flat
> >> part of the sawtooth output was now obvious. The time of the flat was
> >> frequency dependent, but then again it would because the FET follower
> >> could follow the input. I always thought there will always be a
> >> noticeable Vgs between input and output in a source follower. Surely if
> >> the sawtooth is at 12V, the supply, the FET output will not be able to
> >> follow.  What type of FET are Roland using? Is this 2SK30 not a JFET? Or
> >> am I completely missing the point here?
> >
> >Try different types of BF244. A BF244A can have as low as 1.5V threshold,
> >while a BF244C can have 6V and more. (from memory; exact range see data
> >sheet).
> >
> >JH.