Vu Perc Relay

Percussion with VU Meter & Relay

_ABOUT:
The vu-perc-relay is a drum sound module for eurorack that uses a vu meter to hit something (in this case a copper strip and a LED leg) that is connected to a piezo element.
And a relay is triggered and amplified via another piezo element.

_VU METER CENTERING:
There is a trimmer potmeter that you can use to set the center position for the vu meter,
the vu meter moves left and right to hit the different metal parts.

_CROSS FADE TRIMMER
There is a small trimmer on the board that holds the relay and the vu meter, this can be used to cross fade between the vu meter and the relay,
it does not really cross fade the volume that much, it will just make one less dominant in how sharp it sounds.

_PUSH BUTTON:
Each push button disables the gate input next to it.

_GATE NPUT:
Gate input from 5v to 12v can be used, if the gate signal goes below 5v the strength of how hard it hits the vu meter, or how hard it clicks the relay can be adjusted,
2v gate signal will make the volume less then 5v.

_GATE INPUT / CV VOLUME INPUT:
The signal for the vu meter is gated by a envelope that is trigert by the gate input, to prevent feedback when its used over a large PA.. (it helps to put bubble plastic under your case to prevent feedback when using piezo's)
When you plugin a signal to the CV input the signal connected is used to control the envelope (top socket).
The relay is not gated by the envelope, it is only gated by the gate signal you put into the gate input for the relay.
The volume is set by a Vactrol.

_VOLUME:
The output signal is about 10v PP +5v/-5v, but can also go slightly higer to around 14v PP.
There is a soft clipping circuit that cuts the signal. You can set the preamp volume with a trimmer pot.

_EQ:
There is a small EQ in the module, on potmeter sets the highpass filter, and the other potmeter sets the lowpass filter.

_POWER:
Power consumption is low (still need to actually test, is probably around 30ma).

_IMPORTANT:
Stripped tubing from a electrical wire is put over the tip of the vu meters hitter, this prevents the vu meter from making direct contact with the spring.
If the hitter makes direct contact with the spinge there will be a large click, because its sort of short circuiting a bit.
So make sure the hitter is hitting the spring in the correct position.

https://gieskes.nl/eurorack/?file=vu-perc-relay