owlexifry
Well-known member
a little while back someone was talking to me about their failed/struggled attempts to build this circuit (…something about not being able to set the bias correctly without getting ticking)
with that in mind, the necessity to use matched JFETs… geez i certainly had doubts about having any real success, but i went ahead and ordered x2 matched quads of 2N5952 and some 2N4125 from banzai anyway. just to see if i could do it really. never played a phaser before…
before i got started, i had a look at the schematic and decided i was also going to measure and match the (22K, 47nf+10K, 10K) components at each stage block, as well as the JFETs.
built the recommended jfet matcher, measured all 8, and picked the closest set of 4.
so with all the doubt and apprehension i had towards this circuit, i decided i wasn’t going to bother wiring it up inside any kind of enclosure until i could actually hear it functioning properly.
no switch, no LED, no nonsense, just wanna hear the circuit, so this is where it’s up to:
well, of course, because i doubted, it worked immediately.
got it running today
yeah it’s probably too soon to be posting a build report, but at least i have a rough demo to share
only trouble is, there’s a bit of ticking with the ‘script switch’ engaged.
i haven’t really had a close look just yet, but i suspect this might have something to do with the bias setting(?), and perhaps balancing the bias setting between ‘script switch’ engaged on or off? we’ll see..
so far i only really preset the bias knob to 2.4v at the gates before installing the JFETs, and found it sounded pretty good on first test.
i’ve decided i love this effect and will be putting it in a nice hammond enclosure real soon.
with that in mind, the necessity to use matched JFETs… geez i certainly had doubts about having any real success, but i went ahead and ordered x2 matched quads of 2N5952 and some 2N4125 from banzai anyway. just to see if i could do it really. never played a phaser before…
before i got started, i had a look at the schematic and decided i was also going to measure and match the (22K, 47nf+10K, 10K) components at each stage block, as well as the JFETs.
built the recommended jfet matcher, measured all 8, and picked the closest set of 4.
so with all the doubt and apprehension i had towards this circuit, i decided i wasn’t going to bother wiring it up inside any kind of enclosure until i could actually hear it functioning properly.
no switch, no LED, no nonsense, just wanna hear the circuit, so this is where it’s up to:
well, of course, because i doubted, it worked immediately.
got it running today
yeah it’s probably too soon to be posting a build report, but at least i have a rough demo to share
only trouble is, there’s a bit of ticking with the ‘script switch’ engaged.
i haven’t really had a close look just yet, but i suspect this might have something to do with the bias setting(?), and perhaps balancing the bias setting between ‘script switch’ engaged on or off? we’ll see..
so far i only really preset the bias knob to 2.4v at the gates before installing the JFETs, and found it sounded pretty good on first test.
i’ve decided i love this effect and will be putting it in a nice hammond enclosure real soon.
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). Anyways it was all trimmer action for me I was able to get rid of the thump and any ticking that I noticed at least that way. One suggestion give read is to lift the wiper on the trimmer and attach it to the leg of another trimmer say 10 or 25k. Then attach the wiper of that one to the board and attach leg 1 to ground set the 250k to where you are getting good phasing (you might find the sweet spot and to a hair lower too) and then fine tune it with the other trimmer. Probably be easier with a little daughterboard, I found the 250k got it close enough for me but if you really want to fine tune it.
