Matched JFETs

[smallbearelec]

I noticed a post about the Galileo MK II, so maybe this is timely. SBE has started to offer pairs and quartets with Vp in the range of -1.4 V to -3.5 V for phasers. Many thanks to R. G. Keen and Mark Hammer for their consults! As we test more raw stock, we are going to have remainders that are above and below the phaser buckets. We're presently testing 2N5457s, and it looks like the ones on the lower end for Vp start to look like the J201 according to the datasheet. If you have specific requirements, please drop a message to the smallbearelec address. I can't promise to fill all needs immediately, but we do have a lot of types, and now a semi-automated setup for sorting and packaging.

[Mark Hammer]

Steve sent me a bunch of pre-measured ones to try out, such that I could select different Vgs ranges and "spreads" (i.e., degree of matching).  I was pleasantly surprised by how well the 5457s fared, in comparison to the matched 5952s I had in the circuit (sockets are wonderful things!).  Just as "musical" as the 5952s.  You'll need to tinker with the biasing trimpot, but realistically that would be true of any matched set of 5952s with a slightly different Vgs as well.

Nice to know there are alternatives.  Thanks, Steve.  Now all we need is someone to whip up a layout for a 6-stage P90.   

[R.G.]

How about an 8-stage?

[Mark Hammer]

I wouldn't kick it out of bed.  Although I find that moving beyond 6 stages tends to require attention to cap values and the feedback loop since lotsa stages can (at least in my experience) result in some troublingly "woofy" resonances in the low end.

Not insurmountable, but one needs to reduce the cap values a smidgen (e.g., .047uf to .039uf), maybe trim some of the low end off the feedback loop, and tinker with the bias trimpot to nail the optimal range.  Meh.  Details.

Certainly, for those who like the sound of a phaser converted to vibrato mode, more stages can make it interesting.

[midwayfair]

Yay!

Besides using them in phasers, for anyone interested in building the 1776 Cardinal Version 2 (which will drop near the end of this month), these matched pairs will work great in that circuit. I'll make sure Josh puts a note in the build doc.