[sdiy] First DIY synth (555 osc.'s)

[Scott Gravenhorst]

I would suggest that the instability you are experiencing
is not from the 555, but rather some other component or
influence.  If what you say about the 555 is true, my
FatMan would never stay in tune for the hours at a time
that it reliably will.  I'm not defending the 555 as 
good choice for a VCO, but it simply is not that bad.
I've also built simple oscillators with the 555 and
they are far more stable than changing by octaves over
minutes.

JMO.  YMMV.

perpetual <perpetual at uswest.net> wrote:
>
>> > I wanted to build a bear bones system for more of a learning experience then
>> > anything else.  I planed to build the VCO and ADSR from simple circuts I
>> > found based around 555 timer chips and I was going to use CEM chips for any
>> > or all of the VCA,VCF and LFO (if I included one).
>> 
>> Huh? VCO with 555, but LFO with CEM chip?
>> 
>> > I would use batterys in lue of a powersupply.
>> 
>> If you do so, use a VCO that is unsensitive to power supply voltage. Or
>> you'll have to re-tune all the time when the battery goes weak...
>
>so i was playing with a 555 oscillator last week.  more info here:
>www.geocities.com/aurelialuz/shadow.htm
>
>what i've found is that all this talk about instability is true.  this
>thing is really temperature sensitive.  and we're not talking like a
>couple cents over an hour, i'm talking like octave flucuations from
>minute to minute.  this thing is powered off a battery too, so i've got
>both demons of instability working against me.  if i was really
>interested in creating some sort of stable oscillator, i'd look
>elsewhere.
>
>but lucky for me, i care not a whim for stability.  and what's really
>cool about this thing is when you feed a wave output from another
>oscillator into the CV input.  it becomes something like a sub-osc., but
>instead of creating a low note, it gives all these weird overtones, sort
>of like an "effects" oscillator.  
>
>also, i've always read that 555's put out a pretty weak tone, but i put
>a pretty big poly cap in it (.18uf) and i was suprised how thick it
>sounds.  so if you go the 555 route, the bigger the cap the better.  
>
>best,
>alex
>


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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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