From: georg@miro.nlp.physik.th-darmstadt.de (Georg Mueller)
Subject: Vintage Synth : BIT 01
Date: Wed, 22 Jul 1992 12:25:36 GMT
Distribution: rec.music.synth
Organization: TH Darmstadt, Institut fuer Angewandte Physik

A friend lent me his BIT 01 Rack Expander (serial no 67), so I'm able to 
give you sort of a review of this Crumar synth from 1986. The BIT 01 is 
the expander version of the BIT 99, which is the successor of the 
BIT ONE from 1985.

The front panel

The BIT 01 is a 19" module, 3 units high. On the left side there are 4 two 
digit 7 segment LED's labeled VALUE, ADDR/S.D.PROG No, LOWER PRG, UPPER PRG,
a PARK/WRITE button(*), a tune pot with small knob. Next row OFF(-), ON(+) 
button, numeric buttons 1-5, COMPARE(*), STEREO OUT(*). Next row numeric 
buttons 6-7, SPLIT/LOAD(*) button. Last row two sliders LOWER/UPPER VOL,
ADDRESS(*), LOWER(*), UPPER(*), DOUBLE/SAVE(*) and TAPE(*) button. The 
marked (*) buttons have an indicator LED. 

On the right side there is a block diagram of the synth engine, to remind 
you of the 73 possible ADDRESS values (cool light blue color).
The panel is black, white symbols and green lines. Later they turned from 
black to white and symbols in black, red lines. 
There are two handles left and right (for this high-tech profi look) so you
can carry the BIT with you easily. And not to forget the power switch.

The synth engine

The signal path is DCO1/2 - VCF - VCA plus LFO1/2, classical analog. The DCOs
are almost similar. Range 32', 16', 8' or 4'. Waveform tri, saw, pulse or 
combinations. Tune in semitones, only up, only on octave. Pulsewidth. PW
modulation by velocity. No PW mod by LFO. Now the only difference. DCO1: 
noise, DCO2: detune. Oh, 6 voices.

The VCF has its own ADSR with attack modulation by velocity. Keyboard 
tracking, cutoff, resonance, envelope amount, modulation of env amt  by
vel. One can invert the envelope.
(technical remark: the filters are CEM 3328, Four Pole Low-Pass VCF)

The VCA has a ADSR with attack mod by vel, amt mod by vel and total volume.
 
The LFOs have tri, saw and sqr as waveforms, one can mix them. They can 
modulate any combination of DCO1, DCO2, VCF or VCA. Delay, rate, rate mod
by vel (funny isn't it), depth and wheel amt (that's common for both LFOs).
The difference is 1 has saw up, 2 has saw down.

Misc features

MIDI - One can enable/disable pitch bend, mod wheel, rel pedal, prog 
change, omni mode and select the recv chanel.

SPLIT/DOUBLE - Split point, lower trans, lower/upper vol.
With the two seperate outs a glance of multitimbrality.

The Rear Panel

Memory Protect on/off		Release Pedal in
Midi in/thru			Tape in/out
Lower out			Upper out
Power in 

User interface

What? Press ADDRESS button, type in the two digit parameter number, use
+/- keys to change value. That's the harsh charme of the mid '80s.

Sound

Rich, warm, fat ... well ... analog. But the drawback of DCOs (Nick listen)
CLOCK NOISE in the bass, thats bad. I miss the LFO PWM, OSC SYNC and RING 
MOD. There is a good piano over one octave :-). Another shortcoming of the
digital ADSRs is, imagine a slow high resonance filter sweep by env, you 
expect to hear a DIIAAOOUUWW, but you get DIDIDADADODODUDUW. The fc 
decreases in steps, that can be heard.


Thanks for reading,

	Georg.