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Only Idss matters in this circuit. Vp doesn't matter in the 2nd stage. I'm inclined to pick a JFET with high Vp for the 1st stage to maximize the clean headroom.

I'd want more margin than that if I was building it. 10μA is too close to the measurement error. I'd recommend Q3 should be at least 10% higher than Q4.

I worked in aerospace, on everything from high power experiments on the ground to sensitive instruments in orbit. I was very fortunate to be able to work with, and learn from the best. One of my last projects was an electronics unit on the James Webb Space Telescope.

My meeting fellow effects engineers happens over the internet. I read Brian Wampler's books. I read Craig Anderton's book. I read posts here and on the DIY forums like FSB. I read the stuff on Runoff Groove and Aion. I was an electronics hobbyist for years before I went to college. I...

I was pretty much one my own. Hadn't met anyone with an interest in electronics for music. The school had an electronic music lab, got a tour of that during a music class. In hindsight, I should have asked it they needed an engineer or tech to maintain the equipment. I don't recall much...

They are not. The FB still has it's original knobs. One of the electronics stores I frequented, ITV, carried some surplus stuff in addition to new parts. Back around 1970, Fender made some prototype solid state amps. Those amps ended up at ITV, along with some spare parts. I bought a 60W...

Those schematics above are Electro Harmonix Designs. In 1976, I was an EE student at UCLA. I had a part-time job on campus building stuff for a PhD student. That gave me access to the engineering machine shop, which is where I drilled the chassis above and made the bracket that supports the...

Here's a brief circuit description of how the Electric Mistress V2 (2nd schematic) works. IC1A is the input buffer. IC1B is the pre-emphasis filter. Music has a much stronger signal at lower frequencies. The pre-emphasis filter increases the higher frequencies to even things out and maximize...

Knob functions: SPEED is the LFO rate COLOUR is the feedback or resonance control. At 10, there is enough feedback to sustain oscillations. RANGE is the width of the sweep, similar to the EM's RANGE knob. CENTER is the offset of the sweep. It has maximum effect when RANGE is turned down and no...

J202 are capable of higher gain (transconductance), but we have to run them at a higher drain current to achieve the higher gain. Higher drain current means we must either increase the power supply voltage or decrease the drain resistor. Decreasing the drain resistor reduces the gain, so...

There is some overlap in the specs of J201 & J202. So it's possible to sub the J202 in some circuits. J201s have a very broad Vp range. Some will not work in certain circuits that call for J201. The easiest way to know if a particular JFET will work in a given circuit is to try it. I have a...

Oh yeah, EHX made several revisions over the years. Here are a couple of their early versions. The unit pictured above is based on the 2nd schematic. Take a look at the Madbean Current Lover and 'Lectric Mama for EM circuits with a higher parts count.

Last night I checked out the wiring and power. I had made a 15VDC regulated power supply for it. Back in paleozoic, we ran everything on batteries. The 15V is then regulated down to 12V inside the unit, just like the EM. At some point, I'll probably replace the power jack with the standard...

My CCTT does not measure either Vp or Idss and I'm not aware of any that do. Can you post a pic of the CCTT display when it's testing a JFET? Mine looks like this. The Id measurement is not Idss. The Vg measurement is not Vp. Is is simply the gate voltage at some arbitrary drain current...

I photo'ed it dirty just for you. I plan to power it up tonight.

I built this in 1976 or 1977. It's basically an Electric Mistress with two more knobs. My brother found this in his garage. It's period-correct Electric Mistress right down to the Reticon SAD1024A BBD. Check the date code. Chips are (L-R): RCA CA339 quad comparator National Semi...

I do not recommend building this on Vero. It's hard enough to avoid oscillation on a PCB with ground planes.

Another killer build!

Germanium - Über Alles!

Maybe, but I don't know what it is :LOL:. My recommendation is try whatcha got, get into the ballpark of the voltages noted on the schematic and see how it sounds. I tried a few different transistors and they all worked fine. My AC127s are leaky (most are) so the only good place for one of...