[sdiy] Drone Synth

[Scott Gravenhorst]

Steve Allen <snd_audio at yahoo.com> wrote:
>
>Thanks Scott, I think I'll go with that idea, they can be vc'd too.

Well, I think a 4046 makes a crappy VCO, the internal charge current mirrors are like the mirrors
in a carnival "funhouse".  That being said, you can voltage control it, but don't expect it to
track either linear or expo control voltages.  Worse yet, I've tried, but was unable to supply an
external charge current corrector to make it linear (or expo).  It could be that I misapplied
Bjorn's technique, but then, I never got the entire story on his research of this.  He claimed to
get something musically useful, but yanked his site off of the internet after some frackas here on
SDIY.
 
If you're going to go voltage controlled, I think the 4069 (in dual VCO config) would be better,
it's a dual and doesn't require the extra opamps to make sawtooth.

> Know where I can get that in an ASCII schematic??

You're kidding, right?

>Thanks again for your help.
>  Steve
>
>Scott Gravenhorst <music.maker at gte.net> wrote:
>"john mahoney" wrote:
>>> ...but only square waves
>>
>>If I recall correctly, Scott Gravenhorst has used a PLL to generate saws =
>>from squares. Would that be useful?
>
>Actually, this came from the beloved "Adolph Amin" AKA Bjorn Julin/Nillson.
>I have a simplified schematic at:
>
>http://home1.gte.net/res0658s/electronics/4046PLL_saw_out.gif
>
>It's a dual input high impedance amplifier connected to each side of the
>VCO cap. The outputs are summed and voila, out comes a sawtooth.
>
>I never got around to actually trying the waveshaper because I couldn't get
>the VCO to behave linear enough for use in music. But the principal of
>operation is not complex and there is no reason for it not to work.
>
>IMHO, the 4069 VCO is the best bet, and if you eliminate the PWM part, you
>can make 2 VCOs from one chip package.
>
>
>>He's also worked on some kind of divider for creating different =
>>intervals from a master (high speed) oscillator.
>>
>>The above is from memory, perhaps Scott can add some details.
>>--
>>john
>>
>>
>> ----- Original Message -----=20
>> From: Steve Allen=20
>>
>>
>>
>> Hello All,
>> I'm looking to build a module that will be used to generate a drone =
>>tone to under current the main theme in a musical pieace. I've looked at =
>>using 555 timer to CD4024 divider, a dozen of those would be cool, but =
>>not very flexable once tuned up.
>> How about CD4046 PLL's using the divider scheme, more flexable, but =
>>only square waves. Hum....... A bank of Rene's CMOS VCO's ........ a =
>>little complex but very useful.
>> Any ideas? Hope I'm not being too vague or.... well, never mind. Any =
>>and all ideas will be appreciated.
>>
>> Thanks,
>> Steve
>
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>-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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=========================================================  
- Where merit is not rewarded, excellence fades.
- Hydrogen is pointless without solar.
- What good are laws that only lawyers understand?
- The media's credibility should always be questioned.
- The only good terrorist is a dead terrorist.
- Governments do nothing well, save collect taxes.

-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
-- Linux Rex         | RedWebMail by RedStarWare
-- FatMan: home1.gte.net/res0658s/FatMan/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- Autodidactic Master of Arcane and Hidden Knowledge.