[sdiy] 2SK170 FET alternative

[jays at aracnet.com]

Seb,

THAT parts are targeted for more of the high end.

Remember that the 2SK170 takes less drive than the 2SK30. Maybe increasing the gate voltage on the 2SK30 would give you more range and harder compression. One thing to do is get a bunch of appropriately valued trim pots and put those in and tweak them to see what happens. This can lead to all sorts of fun. You might even stumble on to something you like. Or you might let some of the smoke out of the parts.

Maybe in this case you are looking for more for soft distortion than compression. Like tubes or MOSFET clipping. One thing I looked at in the guitar world (I think it was called the Shaka) where there were a set of GE diodes and MOSFETs are put in series to form a soft distortion/clipping. Haven't tried it yet so don't know how well it works.

Jay S.

Seb Francis wrote:

> Well I've managed to get it working with the 2SK30A without it 
> oscillating any more :)
> It took a change of R34.  The timing of the attack and release doesn't 
> seem right though so I think I will need to rework some other values to 
> compensate for the different FET.
> 
> Definitely good advice about breadboarding it though .. I'm getting the 
> impression that the circuit as it is just won't do what I want it to 
> do.  I guess it's meant to be one of those 'transparent' compressors or 
> something .. I want it to SQUASH drums and cause all kinds of audible 
> artifacts!
> 
> Thanks again,
> Seb
> 
>