Slow Gear works with 2N5457 !

[Michael Weidenauer]

I finished my SG-1 clone yesterday but didn't have an 2SK30A so I searched my data-sheets and found the 2N5457 as quite similar sub.
It works perfect! All the 2N5457's I tried worked with little adjustments of the trimpot. Some FETs gave longer some shorter delay times.

I tried lots of other FETs (BF245A,BF245B,BF245C,2N5458,2N5459) too, but none did work.
I noticed that with all 2N5457s the trim was at least 8k away from ground - most times even fully up.
So Maybe it would be a good idea to change the 10k resistor that goes to the trimmer with a 4k7 and put another 4k7 between the pot and ground to get a more usable bias range (about 1.4V to 4.2V instead of 0V to 2.8V).
Maybe that mod would also keep more FETs working.

Michael

[oldrocker]

I used a 5.1 volt zener and a 5952 for the Jfet and 4401's for the other transistors.  The single op amp is a 741.
I put samples of the SG-1 below. How does it compare to yours?  Just curious.
http://randallbarnett.homestead.com/SoundSamples.html

[Paul Marossy]

I don't remember if I tried mine with that FET or not. I gave up on ever getting it to work. Maybe I ought to dig it out again...

[Michael Weidenauer]

Hi Oldrocker!
I just listened to your samples and I think mine has a bit longer delay time when the attack control is fully up (or should it be down? - I don't know how they put in the pot in the original unit.)

Mine sounds much clearer and smoother but I don't know how your clean setup and your fingers sound sound so it's hard to tell.
On my clone the sound doesn't really change when the attack pot is down and sens is up (compared to true bypass).

I used BC550C for the in- and output-buffers, the 2N5457 and BC549B with hfe~320 for the other three trannies - the OP was an TL061.
I also used film caps instead of the 1uF elkos in the audio path to get a clearer sound.

Nice Homepage!

[oldrocker]

Ok, maybe I'll try some different components and see if I can get longer and cleaner sounds. 
Hey Paul,  yeah dig yours out.  I'll bet you'll get it going this time with a little bit of tweaking and debug.  Sometimes a little time away from it brings new answers. 
Mine only works when the pots are set to a specific position, other than that it won't do sh%t.  So maybe I need to look into mine more to make it better too.  Good luck.
One thing the Slow Gear works great for is smoothing out a choppy tremolo.  I put it after my Pulsar and got a great smooth trem.

[Paul Marossy]

It's been about two years since I built it and about one year since I messed with it last. I guess I should get it out again and give it one more try. Who knows, maybe the third time will be the charm? 

[R.G.]

Some 2N5457's will work, as the Vgsoff range includes the sweet spot range, but most 2SK30A's, 2N5952, and 2N5485s will work.