Top octave dividers: why?

Scott Gravenhorst chordman at flash.net
Mon Nov 8 08:16:53 CET 1999


Christian Hofmann <chris at scp.de> wrote:
>On Mon, 08 Nov 1999 22:03:32 +1100
>Paul Perry <pfperry at melbpc.org.au> wrote:
>
>> With 555 timers so cheap, I don't think it unreasonable to
>> have an instrument with 88 note polyphony.
>> Surely this would be as fat as all getout?
>> 
>> paul perry melbourne australia
>
>Hi Paul,
>I once thought about that as well. But I'm not that familiar with 555s
>(by a weird twist of fate I never happended to use them in my whole diy
>career), so I don't know if this could be a problem: 
>Any instrument should have a master tune knob. I'm not sure if 555s can
>be more or less synchronously tuned by a common control voltage.
>
>Maybe I'm old & wise enough now to understand those sophisticated chips
>like the 555. I think I'll have a look at a linear data book tonight...

Pin 5 (I think) is a voltage control input that sets the threshhold
for the timer.  It has limited range, but might be enough
to push up or down by +/- 99 cents.  That would be enough to tune
to most concert settings.  However, I don't know if all 88 oscillators
would track.  My guess is that you could make it happen at some
expense.

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