Just to add to my query back in Feb 2009.
I have the Synth.com and an Oakley VCO kit (made up by me).
The Oakley, to my experience, is the nearest sounding Osc. to the early Mini’s or indeed the
901b’s. The Synth.com tends to have a more “sharper edge” which are unsimilar to early Moogs.
(Although they may be similar to 921b’s but I have never compared)
When using the Oakley and my 901b’s I sometimes have to visually check to see which are sounding.
Both the Synth.com and Oakley have very good and stable tracking but their output power is many times that
of the 901b’s therefore I keep these mixed at low levels so as to not overload any other Moog modules when
replicating the early Moog sound.
Even so, the 901b’s cannot be beaten on their unique timbre.
For any tech DIY’s out there…I tried using the Expo conv. side of the Oakley Osc. to drive the 901b,s..I got some wild and unstable results for my effort. 