Phase 45 just makes fuzz

[madboy]

Cool... actually, one of the ones I was looking at next was the MXR Blue Box, which sounds like the same thing. This phase pedal is really kicking my butt, though. I tried a few things last night ( replacing the diode, the caps, etc. ) now all the readings are out to lunch. Can you damage a pcb easily with too much heat? I try to be careful, but you never know. Grrr. I will win. Just maybe not today...
madboy

[Eb7+9]

I mentioned this a few times before - one way to cure this problem is by starting with a lower voltage Zener, something like 3.9v and adding Ge or Si diodes (1n60 / 1n4148) between Zener and ground oriented opposite way to incrementally add either 200mv (Ge) or (600mV) per diode to the bias voltage ... the total active bias range is not that wide, you have to be within it to begin with or you'll get nothing ... if you have a limited number of devices but a handful of spare diodes this will allow you set the bias optimally with less trouble ... btw, you can generate a bias voltage solely out of ordinary diodes as well - nothing special about using a Zener here - they'll regulate just as well ...

~JC

[R.G.]

And just to keep the old mental channels open, you can make an "amplified diode" out of an ordinary silicon bipolar transistor.

You put the transistor where the zener would be, collector to where the cathode went (that is, positive side) and emitter to where the zener's anode went (negative end).

You put two resistors across the transistor, R1 from collector to base, R2 from base to emitter. If the resistors are such that the current through the resistors is more than ten times the base current, then the two form a voltage divider that's independent of the base-emitter... up until the base-emitter starts conducting!! So the voltage across R2 can never be more than 0.5-0.7V, but it takes only a trickle of current in the base to do that, because when the base emitter starts conducting, so does the collector. The collector pulls down the voltage at the top on R1. What you find is that the voltage across the transistor collector-emitter is always regulated to be Vbe*(1+R1/R2). So by making the ratio of R1 and R2 different, you can adjust the collector emitter voltage to be anything from Vbe on up. It self regulates, like a zener. Using a trimpot for R1 and R2 lets you dial in anything you like.

It's what's used on most hifi output stage biases to thermally compensate for heating on the output devices.

[sta63bmx]

Sorry to dig up an old thread, but I had a similar issue.  I am using a matched pair of 2N5457's right now and I'm getting a nice phase that sounds like the sample linked from tonepad.  Not identical, but who knows what guitar/amp, etc.  I did my initial testing with an Explorer with EMGs and got tons of distortion, all the time.  But when I switched over to a guitar with vintage-output humbuckers, it cleaned up really well.  If I hit it really hard I get a little distortion, but it's pretty clean otherwise.

Mine phased right away because I matched the FETs beforehand.   I used a pair of 2N5457's matched in RG's fixture.  Vgs was something like -1.466 and -1.499, so they're within 3% of each other.  I haven't tried any J201's yet, but I might.  The circuit is kind of ok, but...eh.  I would rather have an Electric Mistress!  After all the work on that EM build recently, I'm kind of turned off on modulation pedals right now. lol