Doepfer

RTFM

"_Technical remarks:
_The core of the A-110 is a sawtooth oscillator (in contrast to the 
A-111-1 <http://www.doepfer.de/a111.htm>, which is based on a triangle 
oscillator). The other waveforms are derived from the sawtooth by 
internal waveform converters. As the sawtooth reset (i.e. the 
back-to-zero slope) is not infinite fast but takes a little bit of time 
the derived waveforms triangle and sine are not perfect ! At the top of 
the waveform they have a small glitch or notch that is caused by the 
sawtooth reset and cannot be eliminated by the waveform converters. The 
sine is derived from the triangle by a simple diode-based converter and 
the sine shape is not perfect (only a rounded triangle).
If a perfect triangle is required the A-111-1 
<http://www.doepfer.de/a111.htm> is recommended. For a perfect sine the 
quadrature LFO/VCO A-143-9 <http://www.doepfer.de/a1439.htm> is recommended.
"











laryn91 schrieb:
>
> > And we will point out in the module information and user's guide of 
> A-110
> > and A-111 that the sine outputs should be called more precisely 
> "sine-like".
>
> Dieter,
>
> It's probably just me, but where do you point that out for the A-111? 
> In my A-111 manual
> you say just the opposite:
>
> "Sine waves are pure waves: they just contain the
> fundamental, without any harmonics (see Fig. 5).
> They are thus not suitable for subtractive synthesis
> (shaping sound with a filter) - as there's nothing to take
> away!"
>
> To the contrary, the A-111 sine is still suitable for subtractive 
> synthesis. To be accurate,
> you should say "not suitable for additive synthesis" instead.
>
> >If you want a perfect sine you need a VCO
> > with a sine core.
>
> Instead of an impossible "perfect sine", how about just a sine with no 
> *audible* overtones
> (<1% THD) like Arp, Moog, Aries, Polyfusion, EML,etc. used to make? 
> That would now
> make the A-111 useful for additive synthesis and FM.
>
> All you need to do is copy their simple but superior triangle-to-sine 
> converter design. ;-)
>
> --- In Doepfer_a100@yahoogroups.com 
> <mailto:Doepfer_a100%40yahoogroups.com>, <yahoo@...> wrote:
> >
> > I will not participate in the emotional discussion about sine waves 
> but want
> > to mention some technical details (some of these have been already 
> mentioned
> > earlier):
> >
> > All standard VCO circuits I know are based on a sawtooth or triangle 
> core.
> > When the sine wave is derived from one of these VCO cores you will never
> > obtain a perfect sine. The antiparallel diodes are the simplest 
> solution to
> > derive a sine-like wave from a triangle, the FET circuit is a bit 
> better but
> > even far away from beeing perfect. Each kind of waveform converter is a
> > compromise (except rectangle). If you want a perfect sine you need a VCO
> > with a sine core. And in return: if you want a perfect triangle you 
> need a
> > VCO with a triangle core, if you want a perfect sawtooth ...
> >
> > The A-143-9 is the only oscillator in the A-100 that uses a sine core.
> > Though it was not planned as a VCO but mainly VCLFO it can be 
> (ab)used as
> > sine VCO. The main drawback of the A-143-9 is the missing temperature
> > compensation of the exponential generator. We consider to develop a 
> sine VCO
> > based on the A-143-9 circuit but with a temperature compensated 
> exponential
> > generator. I expect that the price would be in the Euro 100 range. 
> We are
> > also working on a VCO with sine core and linear FM with thru-zero 
> feature.
> > But this is another "construction site" because the linear FM and 
> thru-zero
> > feature is much more complicated than adding "only" the temperature
> > compensation.
> >
> > And we will point out in the module information and user's guide of 
> A-110
> > and A-111 that the sine outputs should be called more precisely 
> "sine-like".
> > But even rectangles or triangles are not perfect (each rectangle is 
> kind of
> > trapezoid as each rising and falling edge has a slope that depends 
> on the
> > inherent slew limiting characteristic of analog circuitry).
> >
> > Best wishes
> > Dieter Doepfer
> >
>
>