[sdiy] VCO - sine output - why bother?

[Roman Sowa]

Sine core oscillators designs are older than any of us here, after all 
this synth stuff derived from radio, right?
So basicaly take an amplifier, and put something in feedback loop that 
has frequency dependent phase shift, say double-T RC network, add some 
nonlinearity to keep the amplitude at constant level or more fancy auto 
gain regulator, and you have sine core oscillator.
Replace R in the network with OTA and you have VCO.

Amplifier guys work hard to keep their stuff away from oscillating, we 
can do the oposite.

Roman

W dniu 2016-08-26 o 13:36, Quincas pisze:
> I have another question about the sinewave issue (btw I love my sines,
> use them all the time, but only the filters in oscillation give me
> perfect sines)
> Is there not a way to make a sine core oscillator and derive the other
> waves from it? Like a filter with fixed high resonance for the sine, a
> comparator for the square etc...
> Why doesn't anybody do that?
>
> Quincas Moreira
>
> On 26/08/2016, at 6:25 a.m., ijfritz at comcast.net
> <mailto:ijfritz at comcast.net> wrote:
>
>> Huge difference between Sin and Tri when doing Ring Modulation or
>> audio rate FM.
>>
>> Ian
>>
>>
>> Sent from XFINITY Connect Mobile App
>>
>>
>>     ------ Original Message ------
>>
>>     *From: *Steve
>>     *To: *'synth-diy DIY'
>>     *Sent: *August 26, 2016 at 2:32 AM
>>     *Subject: *[sdiy] VCO - sine output - why bother?
>>
>>
>>     Now I'm not a super synth expert, also not in sound design with such.
>>     What I've always wondered, if I look at VCO circuits, why people
>>     go to the lenghts that they do wave-shaping a more or less pure
>>     sine as a waveform output, my heart ached when I saw a circuit
>>     that used an OTA + yet other stuff just for that.
>>     What more does a dedicated sine output provide that one can't get
>>     with using triangle -> lowpass VCF with keyboard tracking on? So
>>     maybe it doesn't shave off all harmonics totally, but is the sound
>>     difference really that big?
>>
>>     Steve
>>
>>     *Gesendet:* Freitag, 26. August 2016 um 06:42 Uhr
>>     *Von:* "David G Dixon" <dixon at mail.ubc.ca <mailto:dixon at mail.ubc.ca>>
>>     *An:* "'Quincas Moreira'" <quincas at gmail.com
>>     <mailto:quincas at gmail.com>>, "'Richie Burnett'"
>>     <rburnett at richieburnett.co.uk <mailto:rburnett at richieburnett.co.uk>>
>>     *Cc:* "'synth-diy DIY'" <synth-diy at dropmix.xs4all.nl
>>     <mailto:synth-diy at dropmix.xs4all.nl>>
>>     *Betreff:* Re: [sdiy] SAW core VCO flyback time
>>     I stopped building sawcore VCOs because I didn't like flyback.
>>     That's why I only build tricores now, and shape them into saws.
>>     They sound better anyway, and sync in a more interesting way.
>>
>>
>>         ------------------------------------------------------------------------
>>         *From:* Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl]
>>         *On Behalf Of *Quincas Moreira
>>         *Sent:* Thursday, August 25, 2016 5:41 PM
>>         *To:* Richie Burnett
>>         *Cc:* synth-diy DIY
>>         *Subject:* Re: [sdiy] SAW core VCO flyback time
>>
>>
>>         crickets....
>>
>>         lol.  I wish I was enough of a badass designer to be able to
>>         brag on this thread ;)
>>
>>
>>         Cheers
>>
>>         -Quincas
>>
>>         On Tue, Jul 5, 2016 at 7:10 AM, <rburnett at richieburnett.co.uk>
>>         wrote:
>>
>>             What sort of reset times are people getting with their
>>             sawtooth-core analogue VCO designs?
>>
>>             I'm curious what figure is the current state of the art.
>>
>>             -Richie,
>>             _______________________________________________
>>             Synth-diy mailing list
>>             Synth-diy at dropmix.xs4all.nl
>>             http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>>
>>
>>         --
>>         Quincas Moreira
>>         Test Pilot at VBrazil Modular
>>
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