I'm thinking about designing a headphone amp module and a DI module for the preamp. They would plug into the mixed signal position and...

It was a tight fit, but I got a PD1 preamp and a battery in this PJ cavity. I removed the pickup switch and tone pot, and went with...

I've added a guide for configuring the jumpers on the PD1/2 preamps, to select where the second filter is applied in the signal chain....

This week I spent some time (probably too much time!) overhauling the drivetrain in my lathe, an old Austrian Emco. I bought this...

The FV1 test boards are out to the fabricator. There is a lot of interest in this filter module, so most of my efforts now are going into...

This week I am working on the variable Q filter, which will have a trimmer (or external pot) to vary the Q between a flat response and...

I built the first PD2 Preamp and everything tests out great. It's essentially the same as the PD1, but has gain trimmers for both...

The website is now in a usable state, with lots of information on the Underhill Preamp. Preamp modules, potentiometers, and switches are...

This is cool. All I had to do was make up a quick cable, and I can plug an EMG BTC into the PD1 Preamp. Here I plugged it into the...

The PD1 and FS1 boards are built and tested. The modular layout is really nice, I can pull out and swap individual pieces, and the system...

The PD1 Preamp board is out for fabrication. This version has connectors for two filter/eq boards, and moves the potentiometers off of...