John Loffink wrote:
shape a triangle, then from that triangle he shaped the sine. Is the saw
and sine out of the PCO/NTOs in the same phase relation? I bet not.
I believe this is where the bump is coming from in the NTO's sine - the
triangle. I say this because the sine shaper he used (close derivative of
the Thomas Henry's circuit) is considered the best of all of them. Grant
Richter pointed out recently what a glorious result this shaper has when
coming off a triangle core VCO, such as the Wiard and Aries, among others.
One of those others was made by Jurgen Bergfors and in that his sine shaper
is driven by a current mirror I believe he used the Henry design as well and
his sines are picture perfect . To see just how perfect, go here for a
pciture:
http://hem.bredband.net/bersyn/vco.htm
Another Henry user was Nyle Steiner and the Steiner-Parker sines are by far
the cleanest I've ever heard. I'm not at a Steiner Schematic right now to
verify if his circuit was saw or triangle core however.
If I remember correctly Serge's sines look a lot like the Analogue Systems
variety, a sort of a rounded square wave. Analogue System used a completely
different method for sine shaping, the differential amplifier shaper found
in Electronotes Vol. 1 which among hard-core synth DIY'ers is considered the
less pure of all of them.
This leaves one other that I know of - the diode method used by Buchla
which if done right (as he did) will also yield an extremely clean sinewave.
This was not Buchla's design. Electronotes credits this as first appearing
in Electronics Magazine in 1965. Two diodes forced into non-linearilty,
then to an FET. I've played around with this circuit and if I were to
produce a VCO, this is the one I'd use. Less parts and impressive fidelity
across the entire frequency spectrum.
Off soap box.
- Peter
> I see a barely noticeable peak/spike at the top of my 2002 era NTO sine waveI believe the NTO is saw core, not tri core. This means Serge first had to
> outputs. This doesn't seem like it would add much harmonics. The overall
> shape is a little more rounded than a sine wave, but this is typical of sine
> waves shaped from triangle waves.
shape a triangle, then from that triangle he shaped the sine. Is the saw
and sine out of the PCO/NTOs in the same phase relation? I bet not.
I believe this is where the bump is coming from in the NTO's sine - the
triangle. I say this because the sine shaper he used (close derivative of
the Thomas Henry's circuit) is considered the best of all of them. Grant
Richter pointed out recently what a glorious result this shaper has when
coming off a triangle core VCO, such as the Wiard and Aries, among others.
One of those others was made by Jurgen Bergfors and in that his sine shaper
is driven by a current mirror I believe he used the Henry design as well and
his sines are picture perfect . To see just how perfect, go here for a
pciture:
http://hem.bredband.net/bersyn/vco.htm
Another Henry user was Nyle Steiner and the Steiner-Parker sines are by far
the cleanest I've ever heard. I'm not at a Steiner Schematic right now to
verify if his circuit was saw or triangle core however.
If I remember correctly Serge's sines look a lot like the Analogue Systems
variety, a sort of a rounded square wave. Analogue System used a completely
different method for sine shaping, the differential amplifier shaper found
in Electronotes Vol. 1 which among hard-core synth DIY'ers is considered the
less pure of all of them.
This leaves one other that I know of - the diode method used by Buchla
which if done right (as he did) will also yield an extremely clean sinewave.
This was not Buchla's design. Electronotes credits this as first appearing
in Electronics Magazine in 1965. Two diodes forced into non-linearilty,
then to an FET. I've played around with this circuit and if I were to
produce a VCO, this is the one I'd use. Less parts and impressive fidelity
across the entire frequency spectrum.
Off soap box.
- Peter