RobertJay wrote:
Thank you ALL!!! I just ordered a bunch of 2SK30A's. This is a great circuit and the small size lets me use these lil pcbc's in my multi effect builds. I was able to find matched quads and bought a bunch of unchecked ones. What are the characteristics wer are looking for when matching quads? hFE? I think I read it's the voltage between the Base / Emitter? I'm happy to test them all to find suitable quads...
How are you matching JFETs? It's not something you can do easily with a multimeter. You are trying to match the Vgs(off) or Gate Source Cutoff Voltage. It will likely be in the 1 ~ 1.5V range. This is the voltage at which, when applied to the gate of the JFET, the Source and Drain will have it's least amount of resistance. You want to match this particular spec, because when it's matched, it means that all 4 phase stages will be working together. The more closely matched, the more closely in synch the phase stages will be working together at the exact same time and thus producing a more intense phase effect.
The problem with the new production 2N5952 is that the Vgs(off) MIN/MAX differential is too small. It doesn't matter if you match them. It goes through it's full "sweep" with only half of the LFO cycle, so it creates a sort of squared off saw wave instead of the smooth asymmetrical sine wave that you're expecting from the Phase90. The problem has nothing to do with the trim pot or resistors.
_________________
*patience is a virtue*
Please do not PM me. email is prefered.
keith@buildyourownclone.com