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Nice writeup! I've also played with some of these AMZ saturation controls, and also found them to be subtle with high Vf diodes (like the 1N4148), especially when fed by a single gain stage. Because you're adding resistors to the mix, it takes a larger voltage signal to forward bias the diodes...

That would actually make some sense as you're forcing more signal through the 1n cap down to ground when the gain control is turned up. You're allowing signal to bypass it when turning the gain down. I believe the Gain control is working as a feedback control.

Hard to tell, but it looks like there is a solder bridge between the SW pad & GND. Try removing it with a hot soldering iron or a razor blade (avoid cutting in to the PCB).

I've had the same experience! Always played a Strat, but never really used the bridge pickup (even on my baritone). I always feel like I need to roll off highs on my guitar or pedal tone controls compared to "noon". I have a Jaguar as well, but it turns out I REALLY don't like it. Funnily...

That's super cool! Any chance you would post a full schematic with the servo? I'd like to give it a go on the breadboard.

Agreed. There is a pretty narrow usable range, especially on the Gate trimmer. I just posted this on another thread, but here is info I've collected on setting the trimpots: BBD/BIAS trim pot - Similar to the pot on a CE-2 or Caesar. Adjust for the least amount of distortion with modulation...

The Low Tide schematic was posted on a few previous threads: https://docs.pedalpcb.com/project/LowTide-Schematic-PedalPCB.pdf Does your PCB layout match this build doc? There was an older build doc as well, but I can't seem to find it. To hear the most intense modulation effect, set the Rate...

Oof, good catch! Hope your components survived, fortunately the rest of the wet signal path looks good based on voltages. Vgg/pin 4 feeds only the gates of the MN3207 internal MOSFETs, so having fed it a much lower bias voltage (with very little current available...) it's probably OK.

Great timing on the write-up, Chuck! Just today Electronic Audio Experiments posted a discrete OTA board he'd made with 3 matched SMD transistor pairs (at least from what I can see): Here's the info he posted: This little friend is a very simple discrete OTA using matched transistor pairs. An...

This is something beginners could benefit from learning. Keeping track of changes/substitution, connections to double-check, and the function of each component makes troubleshooting soooo much easier. I do the same for each build, with spreadsheet containing the BOM, pin voltages, + any math I...

Intermittent issues like this are the WORST to troubleshoot. I've run into this when trying to wedge a large vero build into a 1590BB. Between board flexing, invisible offboard shorting, & sockets, it's like playing Operation.

Damn, that's dead-on my experience as well... It actually sounds great on a master buss or stereo mix, but is kinda disappointing on guitar. The tape emulation side is nice, but the tape saturation is, well... not very tapey. Especially when hit hard, it sounds more like a diode clipper to me...

That voltages file is a troubleshooting dream, man... I think you're right about it being a problem with the BBD stage, everything else looks fine (except for the 2SK208, but I think drain & source readings might just be switched). Here are some suggestions: Pin 4/Vgg is the MOSFET Gate bias...

I use resistor leg cutoffs on my SMD adapter boards & they work great in sockets! Also never had a problem with SMD JFETs & heat, and I use a standard hand iron to solder them.

Those look like quite useful LTSpice plots, how did you set up your command to step through 3 different transistor/resistor combinations?

Ahh, that's easier to read & looks more like the JFET as variable resistor circuits I'm used to. It even has a bit of feedback injection into the gate for lower distortion, which could definitely be an issue if the sidechain signal is vastly different from the wet path. I agree it's probably...

From one of the reviews: "Diode 1 and 2 are drawn backwards on the schematic and on the PCB. Flip them around and it sounds amazing."

The PCB Guitar Mania build doc schematic has the diodes the other way around compared to the PedalPCB one. You can try flipping them around, which, at a first glance, would make more sense anyway.

Read the build doc, as there are two versions of the board:

I'm thinking that Q3 is being used as a voltage-controlled resistor, but I haven't seen one set up like this before. Usually the JFET would be set up with the drain connected to the through signal path & the source routed eventually to ground. The gate is typically the control signal, but it...