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ThunderBell Analog Cowbell

The Delptronics ThunderBell is a classic analog cowbell sound. The circuit is inspired by the great cowbell sound in the Korg KR-55. Like the KR-55, the TR-808, and most other analog drum machines, we model a cowbell by using two tuned square waves. We also include some pseudo-ring-modulation, as did the KR-55.


In the old drum machines, the cowbell was not tunable. Newer cowbell modules give you knobs to tune the two square waves. However, if the two frequencies are not in the correct relationship to one another, then it does not sound like a bell at all. The Delptronics ThunderBell keeps the two waves in the proper relationship across a wide freqency range. So, it is a truly tunable cowbell. There is also some room at the lower end where the sound gets weird and fun, if not bell-like. The ThunderBell also gives you broad control of the decay, so you can create short "tinks" or long "dings".

Voltage Controllable

The ThunderBell Eurorack Module gives you voltage control of both the pitch and decay. The CV inputs are 0 to 5V and cover the whole range of the module's sounds, it is not 1V/octave. We also include a trigger button so you can throw a bell into your mix whenever the mood strikes you.

The ThunderBell in a Cowbell (or mini kit) has an analog gate input and pitch voltage control input. Both pitch and decay are controllable with knobs, and of course there is a trigger button.


ThunderBell Eurorack Module
Fully assembled and tested module
ThunderBell in a Cowbell
Fully assembled and tested
Built into a cowbell
ThunderBell in a Cowbell
with Speaker

Fully assembled and tested
Built into a cowbell with a speaker and a mini amp inside it
$107 Out of stock

ThunderBell Eurorack Kit
Circuit board and all parts
Including Eurorack panel
$75 Discontinued

ThunderBell Mini Kit
Circuit board and parts
You supply the enclosure
ThunderBell T-shirt

Video Demo

The ThunderBell in action.



ThunderBell Eurorack Module ThunderBell in a Cowbell
The Delptronics ThunderBell Eurorack Module
is 6 HP wide and 22mm deep.
The Delptronics ThunderBell in a Cowbell
is 3.7" tall, 3.1" wide, and 2.3" deep (94x79x58 mm).


ThunderBell T-shirt


The Kits

The ThunderBell kit comes in two versions: Module and Mini. The Mini circuit board is used in our ThunderBell in a cowbell. The table below details the differences between the two kits. The main difference is that the Module kit includes extra parts to amplify the output up to synth levels and for voltage controlled decay.
Feature Module Kit   Mini Kit
Trigger Button Yes   Yes
Trigger/Gate Jack Yes   Yes
Pitch Knob Yes   Yes
Voltage Controled Pitch Yes   Yes
Decay Knob Yes   Yes
Voltage Controled Decay Yes   No
Volume Control Yes   No (but can be added if desired)
Output Level Synth Level (9V P-P)   Line Level (2V P-P)
Power ±12V or ±15V   7-15V single supply
ThunderBell Module Circuit Board   ThunderBell Mini Circuit Board
ThunderBell Module Circuit Board   ThunderBell Mini Circuit Board