Replacement for 2SK30A in Slow Gear

[gigimarga]

Hello,

After reading more posts from here about this subject it's not clear anymore for me what to use instead of 2SK30A in a Slow Gear clone: 2N5952, BF244/245 or anything else?
I said that because i have read that this stompbox it's very sensitive and a direct replacement of the 2SK30A with another FET will not work.
Could anybody to make a little light for me?

Thx a lot!

[mdh]

I used a 2N5485 in mine, but I suspect that a 2N5952 would work as well (pay attention to pinout, of course).  I think that there has been some discussion of the necessary attributes of the FET, but I don't remember the details.  My guess would be that you want something with a Vgs_off in the range of -1 to -4V, similar to what you'd be looking for in a FET phaser such as the Phase 90.  Also, depending on the Vgs_off of the FET you choose, you might need to change the value of the zener diode to get it to bias properly.  This thread contains a good explanation of the interaction of the FET and the zener diode.

Edit: Further searches yielded my own build report, which also has some good info on FET choice and zener value.  Who knew?

[oldrocker]

I was able to get mine to work using 2N5952's for the Jfets and 4401's for the NPN's and a 5.1v zenor.  Maybe others will work better but that's what I used.

[R.G.]

Try a 2N5485.

[5thumbs]

If you can't find a replacement that works to your satisfaction, effectsconnection.com sells NOS 2SK30A transistors for a pretty reasonable price ($0.30 each).

http://www.effectsconnection.com/oscommerce/product_info.php?products_id=215.

I used these in a recent Ibanez SM7 rehab when I couldn't get NOS 2SK118s at a reasonable price and the usual replacements didn't work as well as the 2SK30A as replacements.  (The 2SK30A is pretty much a perfect match for the 2SK118.)

Good luck!

[gigimarga]

ok...thx all for your answers...i have only some 2N5952 right now and i will try to make it alive with this!

i still have one important question: what is the smallest PCB for that?
i ask this because GGG's PCB seems huge to me....

[R.G.]

i still have one important question: what is the smallest PCB for that?

From "PCB Layout for Musical Effects":
The smallest PCB for a given circuit is the size of just the components laid out edge-to-edge, with all the traces running under the components.

'Course it may take some skill to get the traces that way. 

[gigimarga]

looooooooooool.....