[sdiy] LM13600 VCO

[Jay Schwichtenberg]

A couple of things I found out about doing LFOs with LM13X00 are:

Need to trim the offset into the integrator. This effects the range of the
LFO. Un-trimmed I got about a 100:1 of what I consider to be useful range.
With the trim pot in there it went up to past 500:1.

Next things is to put diodes (zeners, SI, LEDs) on the output of the schmitt
trigger to limit the plus/minus output voltages. The output rails are not
equal and this will effect the triangle wave's slope at higher freqs. This
is a good thing to do with regular op-amp based LFOs too.

Jay

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of harrybissell
> Sent: Saturday, June 21, 2003 2:30 PM
> To: Jim Patchell
> Cc: music.maker at gte.net; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] LM13600 VCO
>
>
> I'll bet that if its a triangle core... the integrators would be
> OK in the same
> package.  with a sawtooth core its likely to be trouble...
>
> H^) harry
>
> Jim Patchell wrote:
>
> >         I suspect that even having the integrators in the same
> package could
> > potentially cause problems, how much of a problem, I don't know...soft
> > syncing is a fairly sublte problem...
> >
> > Scott Gravenhorst wrote:
> > > That's what I thought too.
> > >
> > > Sitting here thinking about it, isn't the real problem due to the
> > > schmitt trigger and not the integrator?  I then thought perhaps one
> > > LM13600 and 2 single opamp packages might be workable as a dual VCO.
> > >
> > > Jim Patchell <patchell at cox.net> wrote:
> > >
> > >>      As far as making LFO's goes, I have had no trouble
> doing this.  The
> > >>only question would be will the two oscialtors soft sync when their
> > >>frequencies get close...for an LFO this is not an issue...I think.
> > >>
> > >>Scott Gravenhorst wrote:
> > >>
> > >>>I believe the answer to this one is "don't do it", but I'll
> > >>>ask anyway:
> > >>>
> > >>>A tri/square VCO can be made using an LM13600, but one
> > >>>amplifier is used as a schmitt trigger.  An opamp could be
> > >>>used for the schmitt trigger.  Is it a bad idea to use an
> > >>>LM13600 and an dual opamp to make a dual VCO?  I'm thinking
> > >>>that there would probably be coupling problems that would
> > >>>result in soft sync between the two VCOs.
> > >>>
> > >>>=========================================================
> > >>>- Hydrogen is pointless without solar.
> > >>>- Good or bad, that which gets rewarded, gets done.
> > >>>- What good are laws that only lawyers understand?
> > >>>- The media's credibility should always be questioned.
> > >>>- 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/
> > >>>
> > >>>
> > >>
> > >>
> > >>
> > >
> > > =========================================================
> > > - Hydrogen is pointless without solar.
> > > - Good or bad, that which gets rewarded, gets done.
> > > - What good are laws that only lawyers understand?
> > > - The media's credibility should always be questioned.
> > > - 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/
> > >
> > >
>