Dual TBridge Percussion

Concept

The TBridge circuit was used in some famous analog drumcomputers. It is possible to create different drumsounds like bassdrums, toms, claves and more.

On the board are 2 TBridge sounds circuits that can be played separately.

Parts

• 1* TL082P op-amp

resistors

• R3,4,13,14,16,17,25,26,27 RESISTOR_100k

• R6,7 RESISTOR_2M , 4M used for different decay range of first sound

• R18,19 RESISTOR_1.9M, 3.8M used for different decay range of second sound
• R11 RESISTOR_10
• R23 RESISTOR_5.6

• R10, 22 ALPHA_POTI 1k ALPHA_POTI for frequency of the percussion sound

capacitors C8, 9, 20, 21 CAP_100n C12, 15 CAP_4.7u pol C5 CAP_47u pol C1, 24 CAP_10n

• 2* switches (on-off-on) select the decay ranges
• 4* jack connectors (2 * trigger in / 2 * audio out

Schematics

All 4 NAND Gates are connected in series from C to B to A to D. The values of the according capasitors are decreasing resulting in a higher frequency from the first to the last gate. The A/B switch connects the A or B NAND gate to the A/B Out-Jack. The B-IN switch connects supply voltage or the C NAND gate to the B NAND gate. The CV-ON switch turns the control voltage on/off. a transistor is used as a LED driver for the optocoupler.

Board

Mask (bottom): File:Micronoise pro pcb.pdf

Parts (top): File:Micronoise pro parts.pdf

EAGLE Files: File:Micronoise pro eagle.zip

Built Devices

Micronoise pro in a case with additional 4 switches for routing signals of the NAND gates to the control voltage in. There is also a DIP socket for chosing the NAND gate that is controlled by the control voltage.

For this micronoise pro a laser cuted plexi front plate was used. The pads of the NAND gates output were connected to 4 LED with different colors to get a visual feedback of the sound.

Demo Video

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