A while ago I posted a query regarding a substitute for the 901b Osc. and kindly received quite a few replies. My problem was that my home made 901bs(made from the Norlin diagrams 1978) would not play/keep in tune.
I decided to rework the 901a and 901b circuits and made new design PCBs along with top quality (the best I could get) connecters. All gold plated etc. All connections were done methodicaly and considerable time spent to wire up using quality cable etc. All trimpots were swopped for multi turn cermet and high quality components scourced.
Now I am ther proud owner of an array of 901bs that play INTUNE and more or less behave themselves. I had to give a nod to Bob and his team all those years ago, they sure got it about right. The sounds of these 901bs are just fantastic.
During this time I purchased the .COM osc which got to here in England after about 3-4 weeks. I great bit of kit, tracking superb.
NOW…to compare. In sound and tone the 901bs win hands down. They have a rounded full human like tone which is pure vintage Moog. The .COM by comparison is somewhat thinner all round. It doesnt posess the character or power of the 901bs. This is not a small difference it is quite a large difference in fullness and timbre.
I have not had the opportunity of hearing the 921s up close but I suspect that the .COM is more similar to them than the 901bs. I think together Ive got a good Osc. system so far where the 901bs lack in tracking the .COM makes up and visa versa with tone quality.
Hope this information helps .
