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Re: Success! (Was: bi-n-tic filter...help!)

2007-04-14 by Mark

On 4/13/07, Scott Deyo put forth:
>Oops... I meant the - and + _inputs_, sorry. That is, the inverting and
>non-inverting inputs to the opamp. The power supplies are indeed the
>same, and although I use 072, the 358 should also work fine there.

I just double checked, and the inverting and no-inverting inputs, and
their corresponding outputs are also the same pins on the TL072 and
LM358. So I'm still confused.

> > It's my understanding that a a 1V/Oct input and exponential FM input
> > would be the same thing.
>
>They are indeed. I almost left off the expo input in favor of linear,
>but I think most people usually use the expo in addition to 1v/oct, so
>there would be more patching.

I had thought that linear FM would be more of a feature, since
exponential FM can be added by simply putting a DC mixer module
before the 1V/Oct input. Then again, I have no idea what be more
useful for the bintic used as a filter.

>The Ext Excite is a really just a second input to the filter.
>An external VCO to clock the filter would be superfluous, I think, as
>the Bintic has its own VCO built in.

I had thought about that. Apparently the clock input is driven by
negative going edges. So I wonder if the duty cycle of the clock
were something other than 50% -- or even if its pulse width was
modulated -- so that the intervals charging and discharging the
capacitors varied, then would that effect the sound of the filter??

>That's it, though the squares are divided lower, I believe. I don't
>have the 4024 datasheet here, but I'm pretty sure they are.

Well, I don't know which outputs of the ripple counter are used.
It's not shown on the schematic.

>Maybe the 358 would be better. I just had 072s, and they've worked on
>around 10 Bintics I've built.
>Follow the Electronotes link on Ken's VCO page to get a full
>description. My mod is from there.
>
>Oh, and critical is good :)

OK :) I'll look that over.

On 4/14/07, Peng put forth:
>
>When I built my Gate Sequencer I had problems using the LM358 as a
>comparator. I think the transition time may be too slow. Instead of a
>sharp trigger/pulse, there was a ramping up. This caused the CMOS chip
>trigger/count to be very jumpy.

I don't know what sort of circuit that uses, or how useful an LM358
is as a comparator in general, but it's not wired as comparator on
the bintic filter VCO daughterboard.

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