[sdiy] Interesting article on top octave generators.

[Mike Bryant]

Real organs had to have every note (about a hundred) tuned using a hammer, so tuning twelve notes using pots should be easy 🙂
________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Tom Wiltshire <tom at electricdruid.net>
Sent: 29 December 2024 21:15
To: Michael E Caloroso <mec.forumreader at gmail.com>
Cc: synth-diy mailing list <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Interesting article on top octave generators.

The thing is it's got to the point where the *specific* divider ratios used by those TOG chips are now a key part of the "combo organ sound". Each generation's limitations becomes the next generation's nostalgia...

Totally agree that twelve separate oscillators for the top octave is the better way though. It's not that hard, and the evidence from the numerous 1970's organs still in existence is that it improves the sound. Tuning twelve notes isn't so hard that it should be avoided.

Tom

On 29 Dec 2024, at 20:11, Michael E Caloroso <mec.forumreader at gmail.com<mailto:mec.forumreader at gmail.com>> wrote:

TOG or discrete dividers from a single master oscillator aren't going to produce a perfect equal tempered scale because the interval between equal tempered semitones isn't an integer ratio (the interval is an irrational number = 12th root of 2).

If you want a true equal tempered scale, you have to use twelve tunable oscillators per semitone.

MC

On Fri, Dec 27, 2024 at 4:09 PM Tom Wiltshire <tom at electricdruid.net<mailto:tom at electricdruid.net>> wrote:

On 27 Dec 2024, at 20:17, Ingo Debus via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>> wrote:

Am 27.12.2024 um 08:35 schrieb Donald Tillman <don at till.com<mailto:don at till.com>>:

If it was me, I would have directly emulated the chip with, say, 6 CD4040's and some diodes.

That’s what Elektor did in 1974:
https://www.elektormagazine.de/magazine/elektor-197411/55706

They used TTL chips, not CMOS. It was quite a huge project. I remember this so well because this was one of the first Elektor issues I bought myself.

I honestly don't see the point of this type of approach. Discrete dividers has all of the worst features of the TOG chips (locked frequencies, poor frequency tuning, loads of circuit) without the few minor benefits (small size, simplicity, and cheapness).

IF you'Re willing to throw that much circuitry at the problem, why would you *not* simply build a board with twelve top octave oscillators and then just use dividers from there? I don't get it.

I suppose the draw of only having a *single' trimmer to tune the entire thing must have seemed absolutely magical in the late 1970's, and that was enough!!

Tom
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