Somehow we have managed to keep prices the same for all of 2024 and 2025. While modest increases in parts costs are expected across the board, many parts are now subject to tariffs of 25% or more, driving the cost of the modules way up. We have tried to offset this as much as possible by reducing build times and optimizing efficiency, but labor rates have to keep up with inflation, so there is very little net change in the labor cost of our products. The only way we could fur

There are now 17 Wiring diagrams on the Help page that cover all of the common preamp configurations.

Wally Barnum demonstrates the new Moonshot drop-in jazz plate preamp. Direct in, with no post processing. '74 J with DiMarzio DP123s.

Exactly 63 years ago today, Kennedy announced the moonshot. While it's not as big a deal, today Underhill announces the "Moonshot" jazz-plate preamp, featuring: - Stacked volume and tone control for each pickup. - Large knurled knobs with original knob spacing. - Original style non-magnetic brass control plate. So what is different? Under the hood, this preamp is a sophisticated "dual filter" preamp, using active filters to electronically isolate the volume and tone contr

Individual modules are tested before being sold or built up into preamp systems.

This part shows the surface mount soldering in the oven.

All preamp orders now come with a screwdriver that's the perfect size for tightening the screw terminals and adjusting the trim pots!

I'm starting a series of very short videos showing the steps in making preamps.

NOTE: This is now in the FAQ section.... This is a rough draft of a new FAQ to describe what a "filter" is. Let me know what you think! What the Heck is a Filter? A filter is nothing more than a means of modifying a stream of something, be it mechanical or electrical or even mathematical, into a different stream. An obvious example is a coffee filter. You pour a mixture of coffee and water (the stream) into a filter, and it is separated into large wet particles on one side, a

The BA Buffer for active pickups has been re-designed with a screw connection for the positive battery connection. This makes it much easier to hook up the pickups, since you don't need to solder the pickup power wire to the battery wire; power can be supplied through the preamp and all the pickup connections are in one place.

The Focus is on Painless Installation! Solid round shafts let you orient your knobs the way you want. All bushings are 10mm long for easy through-body fitting. Pot Nuts for adapting 7mm pots to 3/8" holes are now included FREE. Shorter stacked pots fit nearly all available stacked knobs. Custom washer keeps pots straight in loose or damaged holes.

A comparison of the Underhill Full English preamp and another preamp with the same features (push-pull Q boost, treble boost). Identical recording setup (actually just an A/B switch), with both preamps set to unity gain and identical filter and treble setpoints. In addition to lower noise, notice how the Underhill preamp also rejects some ambient electromagnetic noise.

We've been so busy working on new stuff for next year that I needed a break, so I made some "Pumpkin Spice" cables to send off with October orders! They have the same Mil-Spec melt-proof insulation, gold plated contacts, and genuine Molex connectors as the regular cables, of course.

Nothing has changed from our informal policy (we haven't actually had any defects to warranty so far!), but I finally got around to writing an official policy. https://www.underhillbass.com/warranty-returns

These inexpensive knobs have excellent fit and finish, and a recess that will clear 1/2" Pot Nuts. For a flush fit, the shaft needs to project no more than 11mm from the nut, so you may need to add some washers inside the cavity. And they have 1/4" holes, so use brass adapter sleeves for the 6mm pots. They have a nice low profile, and are particularly good for push-pulls, being easy to grab. Available on the Dopro Parts store on Amazon.

Preamps are tested and shipped with all of the cables connected. If you are re-arranging or changing modules or cables, MAKE SURE THAT "INs" ARE ONLY CONNECTED TO "OUTs" (labelled on the boards) and your BATTERY POLARITY IS CORRECT (going into the volume module) before you connect power. Incorrect polarity can damage the modules.