Crumar Bit01 (1985)

Crumar Bit01

 
UNDER THE HOOD
Inside Crumar Bit01

Inside Crumar Bit01

Inside Crumar Bit01

Inside Crumar Bit01

Inside Crumar Bit01

Inside Crumar Bit01

Inside Crumar Bit01

Inside Crumar Bit01

 
MAIN DSP, ELECTRONICS, CHIPS PDF DOCUMENTS
CEM3328
HFC4051BE
LM170
MC14520BCP
MC34002P
LM393DP
TL082CP
MC14016B
Intel 8031AH (1)
Intel 8031AH (2)
 
IMPRESSION

The bit 01 is actually the rack version of the Crumar bit99. Very nice polyphonic synthesizer (6 voices) with a very simple architecture (2x DCO, 1x VCF, 1x VCA, 2x LFO, 2x ENV). Although its architecture is simple, it is nevertheless quite complete, sometimes even more elaborated than its competitors (Roland, Yamaha, …) which usually only provide one LFO, COD or envelope (Juno6 / 60/106 / juno1 ).
The Bit01 has two envelopes, one assigned to the filter control and the other to the volume control. There is also two totally independent LFOs, and quite complete. They can be assigned to different destinations like the amplitude of the DCO, the filter, and also to the envelopes.
We find some specificities related to the velocity quite interesting (for instance the LFO speed may vary depending the key velocity, something i’ve never seen before).

The sound of the Crumar is peculiar. Its oscillators use a purely digital process (using binary counters and a technology called « Additive Squarewave Synthesis »). In summary, the various waveforms are generated from a primitive square waveforms (produced at very high frequency). Then these waveforms are divided into multiple levels which are then summed in various ways until the correct waveform is obtain (the Bit01 offers three types of waveforms: triangular / sawtooth / Pulse with variable width). It can’t therefore be said that the bit01 oscillators are analog, but nevertheless the various inaccuracies associated with this method of production generate relatively variable and non-repetitive waveforms, which ultimately gives a very close result to what a purely analog oscillator would generate.
A large part of the motherboard of Bit01 is specifically designed for the production of these oscillators.
Another feature of Bit01 is the ability to combine 3 waveforms at once for both DCOs. This will make it possible to obtain more complex waveforms, and therefore interesting harmonics. Unfortunately, the width of the « square / pulse » waveform can not be assigned to an lfo, and can therefore only vary depending on the keyboard velocity or a static parameter.

It may be interesting to mention the sound is especially warm because of the 2nd motherboard we find inside the Bit01 and which includes all the electronic filters. These are built around the famous Curtis Logic circuit: CEM3328. This filter gives a particularly soft sound, but you may even push it to self-oscillation.
It should also be noted that this synth knows a true « split » mode. Each sound can then be output using a separate output at the rear of the rack. You can also combine two sounds at the same time (dual mode) to create really complex sounds.
In summary it is a very well designed synth and offering warm analog sound with a special signature.

Concerning the « cons » I note three things probably related to a design flaw :

  1. There is an omnipresent phenomenon when one plays in the low frequencies, and which produces a very high frequency sound, like a whistle sound. This phenomenon tends to disappear when one plays in a higher octave range. It is really annoying and requires to have to play with parametric equalizers to try to attenuate this high frequency parasite sound.

  2. At times, the oscillators may detune and you get a somewhat strange sound. This phenomenon occurs very rarely, but nevertheless … it is sometimes pretty confusing.

  3. The play mode can’t be changed, and it seems that the polyphonic mode chosen is to reassign the same played note to the same oscillator. For instance, if I play a string with a long release and play the same note repeatedly, the sound will be cut every time I play the same note. As soon as I change the note, the Bit01 assigns another oscillator and the problem does not appear anymore. It is a pity not to be able to choose the play mode :-/