The long lost 2SK 30(O)

[Fraser, Colin J]

> -----Original Message-----
> From: Trevor Page [mailto:trevor at resonance.fsnet.co.uk]
> Sent: 16 November 2000 08:43
> To: *Star Project; DIY skicka Lista
> Subject: Re: The long lost 2SK 30(O)
> 
> A 2SK30-Y will be fine. There's no difference when 
> substituting 2sk30Y for 2sk30-o in the 303's vco. Use a 
> 2SK30-Y. Please don't go searching for the -O version, 
> there's simply no point! 
> 
> Most JFETs with a suitably low Vgs(off) should work and 
> you'll not detect any difference. For my own 303 clone I'm 
> using a modern device that's much easier to get hold of. It 
> has a pinchoff of about 1.5V. 

I found the characteristics of the FET buffer in the vco will make a
difference to the width (and sound) of the square wave, due to the
interaction with the square wave convertor.
I added a trimmer to my clone that allows me to compensate for this, and
once I set up the clone vco to match the pulse width of my real 303, it was
indistinguishable.
Can't remember the resistor number off-hand I replaced - it's in the square
wave convertor.
I check it out tonight if you're interested.

This only affects the sound of the square wave - I didn't hear any
difference in the sawtooth.

Colin f