dpFX Pedals - 10M piezo Buffer /w variable HPF 200Hz-20Hz and variable Output Impedance

"dpFX pedals" crafts handmade, hand-painted pedals and custom effects (dpeffects.com). All our products are individually serial-numbered.

This is a 10M piezo Buffer with variable HPF 200Hz-20Hz and variable Output Impedance. It is suitable for piezo transducers/pickups (‘Realist’ or similar) and conventional magnetic pickups as well.

This compact, always-on buffer features a 10MΩ input impedance, variable output impedance (~0-220kΩ) and a variable high-pass filter (HPF) adjustable from 200Hz to 20Hz, which can be bypassed via footswitch. The buffer’s very high input impedance makes it ideal for piezo pickups that require proper loading to maintain full frequency response and natural tone when connected to amplifiers or pedals.

The variable output impedance helps you adjust the way your instrument interacts with the pedal that follows. Lots of effects available in the market (e.g. vintage designs, fuzzes, treble boosters, circuits with germanium transistors etc) have a quite low input impedance and “prefer” to see a relatively high output impedance from the previous stage and that's what gives them their distinctive character. The variable output impedance knob is very handy if you want to fine tune the resulting sound when such a pedal is connected to the device’s output.

The active variable HPF, positioned after the buffer, lets you choose a cutoff frequency anywhere between 200Hz and 20Hz using the control knob. With a 12 dB/octave slope, it’s ideal for removing unwanted low-end frequencies that can cause feedback, boominess, or excessive sub-bass. It will work equally well with other active or passive instruments, as well as pedals, preamps, or in FX loops.

The foot-switch gives you the option to toggle the HPF in and out of the signal path in real time, allowing direct comparison between the filtered and unfiltered sound. The buffer always remains active, so your tone stays consistent.

> When & why you need It?

Piezo transducers can sound thin, harsh, or boomy when plugged directly into an amp or pedal due to impedance mismatch. This custom buffer provides the correct 10MΩ load, ensuring your pickup delivers its full tonal range—clear highs, balanced mids, and tight, natural lows. Then, the HPF lets you tame unwanted sub-bass and boominess, tightening the sound and reducing stage feedback.

------------------- Specifications -------------------

- Input impedance: 10MΩ
- Output Impedance range: ~0-220kΩ
- Voltage Required: DC 9-24 Volt (Use 12-24V if you need more headroom)
- Polarity: Negative tip
- Current draw: 7mA @ 9V
- Aluminum Enclosure, dimensions: 122 x 66 x 39.5mm [4.8 x 2.6 x 1.57in]
- Weight: ~250gr.

Shipping method: 1st Priority International Mail (tracked).