Drumulator : Technical Description

Architecture The Drumulator uses a single Z80 microcomputer to sequence notes, scan the controls and reproduce 8 bit drum samples held on EPROM's. The Z80, running at just 2.5MHz, has its own dedicated program 64k bit PROM, which is loaded at power on. The display is made up of two 2 digit LED's.

Song Memory The Drumulator stores the segment, song and mix data on to two battery backed 6116 CMOS chips, this provides just 4kbytes of storage.

Sound Memory The Drumulator has 4 x 16k byte ROM's (93128's) providing a total of 64 KB of sample memory (half the size of the Emulator I's memory). One ROM is dedicated to the cymbal, the other 3 hold the remaining 11 drum samples, all at 8-bit resolution, and in no particularly logical order !

OS Versions The Drumulator has an EPROM based OS, which was upgraded a few times during its product life. You can determine the OS version by pressing the MEM and CASS buttons together, the OS Rev will be displayed on the LED's. It can also be found by looking at the EPROM. It will have a version number like 830405.

     

OS Version Comments 1.05 One of the original versions. 2.00 The version which introduced 64 songs. 3.00 The latest version.

Eight Voices There are a total of eight voice channels, through which the 12 drum samples are played.

Digital to Analog Converters There is only one digital to analog converter, which is a 6072 companding DAC. It is multiplexed to enable 8 separate voice channels to be heard, once demuxed.

Analog Filters Yes, the Drumulator has analog filters ! Two of the channels the ride and hit hats are unfiltered. Four others (snare/rim, bass,claps. cowbell/clave) are each filtered with a static five pole 1dB Chebyshev filter, set at frequencies to optimise the sounds. The remaining two channels (toms) each use a dynamic VCF. They use the SSM2044 with a simple AR envelope generated by the Z80. They create a 5ms sloping attack, followed by a decay. The filter cutoff frequencies can be internally adjusted.

Internal Mixer The eight voice channels are internally mixed into one, along withe the metronome.

Pad Programmer : Technical Description

Architecture The Pad Programmer is very simple technically. It consists of 4 independent trigger sensotos with appropriate circuitry within a common housing and power supply. The power supply is a simple three terminal regulator +5V supply. The input voltage can be anywhere from 8 and 25 VDC. The actual supplied wall unit was 10 VDC.

Sensors The sensors ar piezo-electric crystals mounted in a housing designed to transmit pressure from a vertical strike by a drum stick, and attentuate vibrations conducted by the housing. This assembly is glued togteher and tested at the factory. Service on these assemblies will generally be replacement, as repairs are difficult to accomplish and will frequently be unreliable.

The sensor produces a voltage spike of between 10 and 100 volts, which is loaded into a capacitor and resistor, and rectified by a full wave bridge. The resulting voltage is attentuated and applied to one terninal of a LM339 comparator. The other terminal of the comparator is adjusted for the desired sensitivity threshol. The trim is provided to minimise marginal switching. The comparator output triggers a one-shot which will swallow any comprator oscillation of multiple triggering, and provide suficient pulse width for the LED amplfier and for the output trigger pulse. Both of these signals are buffered from the one-shot output.

PCB Revisions The Revision 2 PCB was issued January 1984. The PCB has considerable space for additional electronics. ith the click channel. A single TL084 is used.