Frequency Divider Waveform

[Hairy Harry]

Hi Larry (et al)

You can put those squarwaves into an exp. lag processor. then one pot will 
vary from square wave to quasi-sine.  I suggest the exp. lag because the 
feedback and stability issues will apear with a linear lag at higher 
frequencies.

The exp. lag is a 6db/oct LPF.

Offsetting the DC level is very easy also... just subtract 1/2 Vcc and you 
are there. If you remove the DC first, then change the amplitude... the bias 
value will not change.

Both non-rocket science ideas that will yield BIG sounds.  I've done the sub 
octave filter trick myself, and love it.

H^)  harry


>From: "J. Larry Hendry" <jlarryh at iquest.net>
>To: "Synth DIY" <synth-diy at node12b53.a2000.nl>
>Subject: Re: Frequency Divider Waveform
>Date: Mon, 31 Jul 2000 07:29:21 -0500
>
>----- Original Message -----
> > From: Mitchell Hudson <mitch at sirius.com>
> > So the frequency divider is working! The amateurs have
> > successfully modified a module!
>
>Well, I guess I'll chime in here since I fall into this same catagory
>"amateur that successfully modified a Blacet FD."
>
> > I have to thank Mr. Blacet, the FD is one of the most useful
> > modules I have built before the modifications.
>
>Ditto.  I especially love the divide by 1.5 and 3.0 which is a feature I
>don't currently have on anything else.
>
> > Now that I am playing with the frequency divider I am
> > curious what is happening with the wave form that is coming
> > out of the FD. Is it a chord? or is it a more complex single
> > tone? I am not sure how to describe what I am thinking here.
> > But is the output like hitting multiple keys on the piano or is
> > it like playing a single note on an instrument that has overtones?
>
>That question comes from an interesting perspective. I've never heard it
>asked that way.  When mixing the original tone with one of the square 
>waves,
>you certainly have two different tones and see the resulting wave (my
>perspective).  However, when mixing the square waves, I see it differently.
>Since one edge of each square wave lines up with the others at some point
>(at the multiple frequencies), I look at adding of the square waves more
>like your other description (single note on an instrument that has
>overtones).  I say this because you can cause one frequency to partially
>mask or cancel out the others.  When you examine the square waves output on
>a scope (with none of the original signal mixed in) you can see this 
>effect.
>
>Conversely, I have a MOTM sub octave module.  Those square waves are
>somewhat out of phase and do no mix the same way.  I like the diversity of
>the difference between the two.
>
>On the subject of modifications, I will throw in one and suggest another I
>have not tried:
>
>Mr. Blacet included a couple of smaller caps on the circuit board (in the
>feedback loop of the mixing op-amp) to taking the edge off the square wave.
>I tried larger cap sizes and found that the wave could be tamed to a
>"sine-like" tone.  So, instead of leaving the jumpers on the board, I put a
>rotary switch on the panel with several capacitor selections.  I can have 
>no
>filtering, all the way to sine-like.  I find this useful.  I cannot however
>take credit for the idea.  The idea belongs to Ken Tkacs from the MOTM 
>list.
>Now that it is complete however, I wonder if could not have made that a
>continuously variable control by putting a pot in series with my largest
>value cap in that feedback loop?  Experts?  I may try this sometime.  My
>other mod simply took advantage of the left over buffers for individual 
>outs
>for the divide by 1.5, 2.0 and 3.0.
>
>If I ever build another, I plan to modify the output buffering.  As
>designed, the circuit gives the square wave outputs as pulsing DC, 0 to ~15
>volts positive.  This is great for sync pulses and such.  If you are using
>it for AC though, it effectively injects some DC offset into your audio.  I
>suppose two outputs could be provided, one through a cap to strip that off.
>However, I was thinking if op amps were used on the output, that a bais
>could be summed with a fixed voltage to shift the pulsing DC back to AC.  A
>switch could be provided so that the pulse output could be selected to AC 
>or
>pulse DC since both are quite useful.  That's probably an overkill way to 
>do
>that.  But, it sounded like fun.  And, using the amp out would allow one to
>scale the output voltage if something different than 15 V peak to peak was
>desired.
>
>Another sinple but useful function of this module is a reversing attenuator
>is you need another for a patch.  Mix nothing but the original signal since
>it is inverted by the module.
>
>I enjoy this module a lot.  Although Mr. Blacet has provided a fine product
>without modification, this is one that screams out "modify me" to amatuers
>like me since it is not rocket science to do so.
>
>Larry H
>

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