- GEM Drum 15 analóg drum machine

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- GEM Drum 15 analóg drum machine

Sold out: March 9, 2017, 4:58 pm

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Acceptable [used]
For sale

Magyarország

Description

huendeskes
Analog drum machine! Demonstration video of this specific unit made by me:


The price is negotiable, trade is unlikely, but feel free to suggest what you have.
Condition is appropriate for its age, one leg is missing. The heads of the two outer knobs are broken off, but they can still be pressed.

Pickup:
- In person in Budapest. During the day near the Sashalom HÉV stop in the XVI. district, in the evening around Keleti station.

- Postage: via bank transfer in advance.

Details in English:
This is a small analogue drum machine/ rhythm device. It is not programmable like a modern drum computer, but by pressing multiple of the locking push buttons simultaneously, a tremendous variety of additional rhythms can be created. Very unusual is that this thing doesn`t contain any ICs, i.e. even the flip- flops of the digital counters/ control logics are entirely made from germanium transistors.

main features:

15 basic rhythms; a variety of additional ones can be created by pressing multiple selection buttons simultaneously.
volume and tempo control sliders. (The tempo range is somewhat limited.)
˝organ˝ jack for modulating the volume of 2 external signals by the rhythm. I guess that this was intended to modulate the chords from an electronic organ. The signal envelopes are modulated by LDRs of 2 light bulb based opto- isolators.
completely analogue, transistorized sound generator without ICs. (2 soft droning drums, transistor noise hihats/snare, woodblock)
integrated power supply with illuminated switch (which flashes slightly dimmer during drums by the power drain of the opto- isolator light bulbs).

modifications:

the transformer wasn`t grounded and mains voltage wires almost touched the metal case =>re-wired and properly insulated. Also the bulb in one of the opto- isolators (tiny metal boxes with LDR) was burned out =>replaced.
6.3mm output jack replaced with a common cinch one
(more will likely follow later)

notes:
This thing has various trimmers to tweak the drum envelopes. Since it is analogue, likely a lot of pots can be added to control the sounds. The transistorized PCB looks interesting =>I might upgrade the case with an acrylic top or similar to make it visible. The electronics uses somewhat high voltages (18V?), which makes it questionable if sensor contacts can safely be added. The rhythms are determined by the PCB trace wiring of the switches, thus theoretically a matrix plug board could be added to make them sort-of programmable.