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I nicknamed this build the BSMSB – Buffer-Splitter-Mixer-Switcher-Boost. It does pretty much what the name suggests, although the splitter-mixer part doesn't really work particularly well. More on that later. A simple non-inverting op amp circuit provides adjustable gain from unity to +20 dB...

Getting slightly off-topic, but couldn't you just reference the transistor to the negative voltage instead of ground in a common emitter amplifier for example? If not, why not? I don't think this case was covered in your BJT biasing series, Chuck.

Same experience here. Tested a batch of MMBFJ201 from Mouser recently. VP of most was around -0.5V but there were groups of outliers at around -0.35V and -0.8V.

You naughty, naughty boy.

https://audiosurpluseffects.bigcartel.com/product/ok-doomer-pre-order Ok Doomer is a result of multiple cascading gain stages collapsing in on themselves running into an artisanal, organically sourced tonestack producing a high-gain fuzz/distortion designed to make you play the same riff for...

I'm just thankful for being able to add varna sankar to my list of questionable slurs I probably shouldn't be using. It sounds awesome. Muddafukkin varna sankars!

Those bias voltages seem off to me. Where did you source your JFETS? Anyway, the guitar signal can potentially swing from 0V to 22V, minus some losses. The drain voltage just defines the midpoint of this output swing.

You can also try a single 100K across the outside lugs. Using a 25K pot will affect the transistor bias slightly since the presence pot also acts as the collector resistor, and so will using two taper resistors for any settings other than 100% or 0%. The taper is going to change either way, and...

Interesting circuit. If you want to maximize clean headroom, biasing an op amp to the mid-point of the positive and negative rails is the way to go, but there's no rule that says you have to do that. Maybe they wanted to increase even order harmonics through asymmetrical clipping for more amp...

That should be fine!

I'm guessing the value of C15 is not that critical and it's more about the properties of MLCCs compared to electrolytics, i. e. lower ESR and ESL for better performance at high frequencies, reduced ripple, etc.

Not too bad for commercial pedal builders considering the cost of the PCB is only one smallish part of what goes into the price calculation, but still kind of a big oof for guys like Robert who mostly just sell PCBs I imagine. Let's see what the future brings.

Feels weird. Like the end of an era. I don't like it, even though I've been using less and less Wima caps in my builds.

That's expected behaviour according to the schematic. Signal goes to the wiper of the trimpot and out from pin 3, so resistance goes down when turned CW and allows the cap to do more of its thing, i. e. throw away high frequencies.

I don't think a pull down will help much here. It's a basic treble booster into a multi gain stage JFET preamp. It's always going to be noisy. Trying different BJTs and JFETs might help.

Transcendence is a good option if you just want more volume but no coloration. Gain is adjustable from unity to +24 dB. I uploaded some samples in my build report here: https://forum.pedalpcb.com/threads/pedalpcb-transcendence-boost-creation-audio-labs-mk-4-23-clean-boost.24896/post-317445

Could also reduce R7 to 47K or so, or use a 100K trimmer to find your preferred setting. Lower values will shift the balance between the bass and treble controls to reduce the treble and increase the bass. It all depends on whether you think there's too much treble before or after the gain...

Now that's some good swarf right there. Mmmmhm.

That's a neat idea. Looks awesome!