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Thanks!! You are correct about R15P and R17P. R18P however is left open. R18P servers to bypass the 2nd gain stage but the 2nd stage is used in the B2. If you still have no signal with R18P removed, then something else is wrong. Schematic is fixed at PCBway and BOM is fixed at the link on my...

Since this is a generic preamp, it can be used for bigger amps, too... This is the first amp that made me want a PCB. I started with hand-made modules you can see on the right side of the guts pic that all moved to the PCB.

More pics of this tiny amp build in progress since I had to make another one this past week...

I've made a few bass guitar amplifiers and decided to simplify the build with a preamp PCB that forms the front panel of an amp. It's shared at PCBWay here: https://www.pcbway.com/project/shareproject/Bass_Guitar_Amplifier_Pre_amp_Board_1414fa9f.html The pictures attached show one example build...

This suggests something is wrong with your build. The path of the dry signal has a gain of 1 with the volume all the way up and the mix set to fully dry. So output should be same as the incoming signal... Unless you have done something wrong in the build. Double check all the resistor values...

Although I've moved on from tiny-pedal builds, I was able to put top jacks in 1590B. It's a squeeze, but possible. You have to use very narrow jacks. https://www.mouser.com/ProductDetail/REAN/RJ3VM?qs=0rbOLB9uh%252BCOWk8%2FAwcx4Q%3D%3D

Use what ever you want.

As I said at the time, that can be used if you add all the diodes of the original schematic. Order the board from pedal PCB and use that, not my board. Or hand-wire in the diodes on the switch. We're going around in circles.

Those won't work. They are not binary encoders, they are pulse encoders. I'll say it again... 8-position, real code, binary encoder.

I can't tell from just a picture.

That looks like 16-position, not 8, and it is also translating the position to a voltage, so is not suitable. 8-position, real-code rotary encoder is needed. You could use this switch if you remove the PCB and attach direct to the pins, but it will still have 16 positions instead of 8.

yes

There is a 4th pin, the common pin. Look at the datasheet.

If you add all the diodes in the schematic you showed, you can do it, but that is a mess. A rotary encoder does it directly with simple wiring.

No. There isn't a direct mapping to such a switch. Use a rotary encoder.

Here's a view of the bottom of the PCB where the eeprom and jumpers are. All the pads on the right side are VCC. Any one of those goes to the common on the rotary encoder. The pads on the left are the individual signals. S0, S1 and S2 go to the other three pins on the rotary encoder.

I should add, you cannot use an "8PDT" rotary. It must be a "Real code rotary encoder" which will have 4 pins: Common, 0, 1, 2. Common goes to Vcc, which is all on one side of the jumper header and then S0, S1, S2 to the 0, 1, 2 pins on the encoder. This switch at mouser is an example of such a...

Those are for jumpers to choose what gets connected, side to side. All the signals (T0, S0, S1, S2) are pulled down to ground with a resistor on the board. Adding a jumper to each will connect them to Vcc. Here's the relevant part of the schematic. You can use a "real-code" rotary encoder with...

The 2 circuits are redundant. And Absolute max voltage on the regulators is 10V.

Of course not. Minimum is 12V 1A for low power. 19V 3A for driving 4 ohm to full power. 24V 2A for driving 8 ohm.