Doepfer

Am I missing something or is there an actual advantage to those 
distorted sine waves on all Doepfer oscillators? They don't sound or 
look much like sine waves at all. Is there a user advantage or is this 
just a trade-off design for cutting costs (i.e. lame diode tri-to-sine 
converters)?

With such high distortion, Doepfer sine waves don't make useful 
additive or FM sources, and not enough harmonic content as useful 
subtractive sources. The distorted shape makes noticeable unnatural 
sounding LFO modulations. I find I never use them and wish for higher-
quality pure sine waves.

Sadly from the scope shots, I noticed even the 111-2 still maintains 
these low-quality sine waves. What am I missing?

Here are my thoughts, but I stand to be corrected:

> look much like sine waves at all. Is there a user advantage or is 
this 
> just a trade-off design for cutting costs (i.e. lame diode tri-to-
sine 
> converters)?

It really amounts to a 'practical necessity' to what is a hard 
problem...

> Sadly from the scope shots, I noticed even the 111-2 still 
maintains 
> these low-quality sine waves. What am I missing?

...which is that to design analogue circuitry to produce a high-
purity sine wave voltage-controlled oscillator which will track over 
many octaves is a very demanding requirement (and which is perhaps 
what you are 'missing'?). Producing a fixed-frequency sine wave 
oscillator is hard enough, as the gain needs to be 'just right' to 
limit the amplitude, and normally some non-linearity (i.e. make the 
gain 'drop off' at some point) is needed to stop the wave getting too 
big, and this will inevitably introduce some distortion. Then making 
the frequency voltage-variable just adds more difficulty, especially 
if it is required to have the frequencies track in musically 
acceptable way.

Thus most designs opt for simplicity, using a triangle wave passed 
through some sine-shaping mechanism, and just accept that the 
output 'sine wave' may not be very 'true'. In the case of the A-110, 
the output is further 'muddied' in that the tri wave is generated 
from the sawtooth oscillator core, by 'flipping' one half of the saw 
(hence the little glitch you may have noticed in the tri and sine 
waveshapes, especially at higher frequencies).

The CEM3340 chip at the heart of the A-111 *is* a triangle-core type 
oscillator, but the sine-shaping is done by circuitry external to the 
chip. I don't know whether the A-111-2 is a discrete design, or based 
on same chip, but the problems will be the same.

If you want high-purity sine waves for additive or FM synthesis, then 
doing it analogue is probably not a good way to go - this is 
something that is far better suited to being done digitally, where 
controlling purity and things like the exact ratios of frequencies is 
more easily done!

(Just my thoughts, and like I said at the start, I stand to be 
corrected by more knowledgeable sources!)

Tim

--- In Doepfer_a100@yahoogroups.com, "laryn91" <caymus91@...> wrote:
>
> Am I missing something or is there an actual advantage to those 
> distorted sine waves on all Doepfer oscillators? They don't sound or 
> look much like sine waves at all. Is there a user advantage or is 
this 
> just a trade-off design for cutting costs (i.e. lame diode tri-to-
sine 
> converters)?
> 
> With such high distortion, Doepfer sine waves don't make useful 
> additive or FM sources, and not enough harmonic content as useful 
> subtractive sources. The distorted shape makes noticeable unnatural 
> sounding LFO modulations. I find I never use them and wish for higher-
> quality pure sine waves.
> 
> Sadly from the scope shots, I noticed even the 111-2 still maintains 
> these low-quality sine waves. What am I missing?


i think it is quite normal on vco's that the sine is not pure.
from a musical point of view this must not be a disadvantage,
but if you are doing fm it certainly is.
obtaining pure sinewaves from a vco is almost impossible,
thats why all true fm-synths are digital.
but of course purer sinewaves can be obtained with an
improved sine shaping circuit. i think i have read something
about modding an a110 in this regard, but i cannot recall
where i have read it.

best wishes

ingo

The announced quadrature/thru zero oscillator is based on a "real"
sine/cosine core and will be able to generate perfect sine waves. At the
moment we are about to try different temperature compensated exponential
generators for the oscillator to obtain a frequency range as wide as
possible.

Best wishes
Dieter Doepfer

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von laryn91
> Gesendet: Sonntag, 17. September 2006 01:10
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Doepfer "sine" waves?
>
>
> Am I missing something or is there an actual advantage to those
> distorted sine waves on all Doepfer oscillators? They don't sound or
> look much like sine waves at all. Is there a user advantage or is this
> just a trade-off design for cutting costs (i.e. lame diode tri-to-sine
> converters)?
>
> With such high distortion, Doepfer sine waves don't make useful
> additive or FM sources, and not enough harmonic content as useful
> subtractive sources. The distorted shape makes noticeable unnatural
> sounding LFO modulations. I find I never use them and wish for higher-
> quality pure sine waves.
>
> Sadly from the scope shots, I noticed even the 111-2 still maintains
> these low-quality sine waves. What am I missing?

On 9/18/06, selfoscillate <synaptic_music@yahoo.com> wrote:
> i think it is quite normal on vco's that the sine is not pure.
> from a musical point of view this must not be a disadvantage,
> but if you are doing fm it certainly is.

Is it really that much of an advantage? I've never had the possibility
to do linear FM on an analog "hi-end"-VCO (by which I mean a VCO with
an as-pure-as-possible sine wave...), so I cannot tell how the
difference actually sounds, but from my understanding, by modulating
one VCO with the sinewave of another, you actually modulate the
frequency of the core-waveform of the VCO (triangle or saw), which is
then sent through the converter. So you don't get "pure FM" anyway...

-Michael

--- In Doepfer_a100@yahoogroups.com, "Michael Wagner" 
<michael.wgnr@...> wrote:
>
> On 9/18/06, selfoscillate <synaptic_music@...> wrote:
> > i think it is quite normal on vco's that the sine is not pure.
> > from a musical point of view this must not be a disadvantage,
> > but if you are doing fm it certainly is.
> 
> Is it really that much of an advantage? I've never had the possibility
> to do linear FM on an analog "hi-end"-VCO (by which I mean a VCO with
> an as-pure-as-possible sine wave...), so I cannot tell how the
> difference actually sounds, but from my understanding, by modulating
> one VCO with the sinewave of another, you actually modulate the
> frequency of the core-waveform of the VCO (triangle or saw), which is
> then sent through the converter. So you don't get "pure FM" anyway...
> 
> -Michael
>


hello michael,

we have to differentiate between fm modulator and fm carrier,
and of course we have to differentiate between standard vco's
and through-zero-vco's. from my understanding the biggest
difference is on the carrier, which produces the fm'ed waveform.
but maybe you'll like the "not so pure" sinewave better
even for the carrier. it is all a matter of taste.
it was my fault so speak of musical disadvantages,
it is more a technical disadvantage which leads to
different sounds.

best wishes

ingo