Wasps, DCOs, OSCs and Schemes

[Dr S Grainger]

>Dear All,
>
>	My first posting to Synth-DIY - better make my 'maiden speech'
>	a good one !!
>
>WASPs
>
>	JH's comments about the 'DCO' in the WASP are valid if you
>	intend to use 'analogue' (voltage) modulation sources. In the
>	WASP they provide LFO, pitchbend and tuning (no envelope
>	mod as I recall ?). An 8-bit programmable divider then provides
>	note frequencies - but no centile increments. Its interesting to note
>	that the manufacturers (Kenton - any others ?) seem only to provide
>	note information to interface to the WASP. Although presumably
>	auxillary control voltages could be used to modulate the VCF.
>
>DCOs
>
>	What is a true DCO ? - a good philosophical point. Our friends
>	in Roland started with the WASP idea (high frequency VCO +
>	divider chain) with the JX-3P then migrated to a fixed clock +
>	divider chain with the JUNO-106 after that ? - I don't know -
>	I don't have the schematics for later DCO machines. Suffice to
>	say that to modulate the 'centile' type of DCO you need 'realtime'
>	frequency updates controlled from a processor which also determines
>	note values, pitchbend etc. from say a MIDI stream. Roland tend
>	to use an 18-bit division to maintain accuracy and limit 'stepping'
>	when carrying out glide and other frequency modulating functions.
>
>OSCar
>
>	A kind of 'centile' DCO but with a PLL providing frequency
>	multiplication (x32). This is then used to scan a 'wavetable'
>	the contents of which are 'standard' waveforms + others formed
>	by what seems to be 'Walsh-type' synthesis. This 'variable
>	frequency' scanning is then re-sampled to provide some very
>	interesting results !!!!
>
>Schemes
>
>	Does anyone out there have some 'original' schematics for the
>	OSCar ? - I have a hand drawn set which seem to have many 
>	inaccuracies.
>
>	Hope this was useful !!!
>
>	Regards
>
>	Steve Grainger