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It's kind of like an LPB-1, but without the sensible biasing*, so it requires "hand selected" transistors so that you can have a Class A booster circuit that sounds like most every other crappy boost, but sell it for $150. Oh, and gigantic overvoltage Russian paper in oil capacitors that you probably ordered because you were curious and they turned out to be too big to fit in anything else, but man do people open up that pedal and think that they're doing something special!

Sorry for the rant ... I despise everything about that circuit and think it sounds horrendous. There are so many better pedals to build or throw away money on, starting with ... an LPB-1.

*They could have used the same number of parts and referenced the base to the collector instead of +9V and had a far better sounding boost with ... more boost available.

If the board doesn't fit ...

Fortunately it does, very well, in that enclosure!

huh, so ... I solved the issue with the buffered bypass one.

I took some measurements and saw that there was an absolute huge voltage on the source of the FET buffer, which was of course charging up and bleeding through the output cap. It was close to 2V by the time it got to the switch!

So I did some investigation and realized that I tied the gate to Vb for the op amp.

Ordinarily, I would have thought that would be fine (it's not like referencing Vb is unheard of in buffers), but apparently I was wrong. Oh well, it's fixed now.

Having such a huge voltage was probably charging up the input cap to the amp, so that explains why all the other pedals/bypasses were popping, and probably also explains why it still popped even when the power supply and FET were removed.

I'm not sure what the lesson I should take away here is, though ....

Awesome, good to see someone else build the Circuit Salad squeezer. It's awesome. What chip did you use for the envelope?

Looks great, Cody.

Hey Jon, are you still playing that ungrounded amp?  This is a just a hypothesis but perhaps there is a ground potential difference which is causing some built up energy to be released in the form of a POP!

Good point, and the amp is the only variable I didn't change. I guess I'm going to have to suck it up and get my good amp down in the basement. I've really been afraid of carrying heavy things up and down stairs since I hurt my back last month, but I guess it's still under 30 lb.

Also, I hope this doesn't mean that the input cap on my HRD has gone bad.

I've been switching to optical bypass and buffered bypass on a bunch of stuff in the hopes of killing switch pops completely.

But today I encountered something completely new: a switch popping with buffered bypass. while unplugged. with the buffer FET removed. and the op amp removed. and the guitar unplugged. Literally every source of DC disconnected, even charged caps or line static.

And just to make sure it wasn't just that pedal, I checked a buffered Fatpants (different buffer, same results). POP. Tried a mechanical bypass pedal. POP. Tried optical. POP. (But it was a little quieter.)

I'm seriously lost.

Could be a bad cap in the power section. Power comes on, cap tries to charge, then slowly shorts to ground. It would cause exactly this behavior.

Interesting thread in that I'm having the opposite issue—old-school Tele pups aren't triggering the filter very well—more of a fixed wah thing. If I take the values discussed above in the opposite direction, lower R15 and raise R2, would it increase the sweep and raise the input gain? I guess it's also possible I have a different issue with my build.

And yes, Bean boards are great to work on!

Just lower (or jumper) R15. Don't touch R2 if you don't have to. But do verify everything about the build before modifying -- this envelope should be able to open at max on almost any type of pickup. In particular, make sure you've used the right value for R17.

The bad news is that you have a lot less room to maneuver than Cortexturizer did. If even a jumper for R2 doesn't fix the problem, try using a 250K for the filter pot to retain more signal. (There's kind of an upper limit to what you can get out of it.)

I'm starting to think I need to plan for a switch on my build to accommodate multiple types of pickups ...

Check that your transistor isn't backwards.

[Here's the results of my experiments:]

I forgot to post this little bit of experimentation here back when I went through it.

First, here's an extended discussion.
http://www.diystompboxes.com/smfforum/index.php?topic=104341.0

Here's the results of my experiments:

I got some time to do some experimentation with the FETs I have here. I used a 10K for the source resistor for the tests just to get a sense of what they did. The supply voltage was 18V and the gate bias resistor was 2.2M. No positive bias on the gate.
I tested:
2n5457 (fairchild from Smallbear and the mystery ones from Tayda)
2n5458
2n5485
2n5952
J201 (fairchild from Smallbear and the mystery ones from Tayda)
MPF102 (fairchild from Smallbear and the ones from Tayda that seem to be the real thing)
2SK30
2SK170

MPF102 ended up with the highest source voltage, about 3.5V (all were above 3V out of the ones I had). I was a little surprised by this based on the datasheets.

The second best was 2N5458, about 2.5V.

2n5457, 5485, and 5952 all ended up around 1.5V-1.7v, despite the differences in Vgs on the datasheets. 2SK30/170 were a little closer to 1.5. The supplier didn't seem to matter in this usage even though I know that many of the Tayda ones have less output when used in a booster.

J201 was all the way down at .7V! And I could indeed hear it distort with some humbuckers.

MPF102 is fairly common, but the 5458 is a little cheaper.

I went back to an MPF102 on the breadboard to mess with the source resistor some, and no matter how big I make the source resistor it never got above a certain level (about 3.6V). None of the other FETs I have on hand get anywhere close to that.

Okay, I know that 3.5V is VERY BIG for a guitar signal, and anything in front of the buffer that might be creating a signal that big is probably a dirt pedal, so any buffer distortion is not likely to be too noticeable or objectionable. But it's certainly nothing like the half supply you guys have mentioned. I don't exactly have a huge collection of FETs, but these are a fairly wide range.

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Also, Brian at Runoff Groove suggested 2N3819, which ends up with an even higher emitter voltage (over 4v).

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Hope some people find this useful. In particular, you might want to consider swapping out J201s in your input sections for a different FET as noted here. For instance, I've been using MPF102s for buffered bypasses (one in my Fatpants 2013 and one in my Zen Drive because that circuit sounds like ass unbuffered).

This is a complicated answer but hopefully it'll be useful.

First, once you get above ~100hfe, the differences between transistors become very, very small except with huge changes in hfe. hfe 300 isn't vastly different from, say, hfe 800 except in special circumstances.

Second, take a look at the BMP schematic and you'll see that the gain is not maxed out on the transistors used. The emitters aren't grounded, and the collector is hardly smashed; additionally, the 470K/100K voltage dividers on the bases could also be increased to get more gain out. Hitting certain bias voltages might help achieve certain sounds, but you'd want to compare with a known good sounding unit. (6V is good.)

Third, always read the datasheet. If you didn't do that yet, then lesson learned for next time! If you did, it's polite to link to the one you used. Here's a perfectly cromulent one: http://www.ece.usu.edu/ece_store/spec/BC547.pdf

You'll notice that it's a little difficult to answer your question: You need to tell us which designation is on the transistor (A, B, C). But the numbers generally line up with the other transistors in that series. And FWIW, that series is VERY consistent, quieter than a slew of other transistors, and sound quite good.

It's actually easier to isolate the wah part and remove everything that isn't that.

R24 is where the wah part starts.
Q2 and Q5 are the wah's transistors.
2, 3, and the part with the LDR are part of the wah, so you can remove those lines.

The fuzz is also controlled by an LDR. Morley loved their LDRs ... that's the thing marked "5".

The power section to the right can all be simplified. You just need standard power filtering and polarity protection. You can duplicate the original effect by knocking the voltage down to 7V with series resistance and/or an LED (1.7v Fv drop + a 100R would put you really really close).

Check out 1776's finish line bypass. Uses any momentary soft switch. Would work well here.

Hm, I'm not sure I'd want a soft-touch switch for a wah. The optical bypass would be pretty awesome, though. (Disclaimer: I am now completely enamoured with that bypass and I'm converting a lot of pedals to it for true bypass.)

Smallbear's price on their really good 3PDTs is a lot less than it used to be -- they have the ones made for them (probably the highest quality 3PDTs you can reliably get in the US) for $5 now, and I believe the alpha switches are the same price. The alphas are NOT like the DPDTs used in the optical bypass, though and are still a little more ... forceful or something. Those DPDTs are super nice and I'm sad I stuck to the blue switches for so long.

Verify that your enclosure is grounded by using your multimeter.

The behavior you're describing is usually caused by an ungrounded enclosure.