[sdiy] new DIY polysynth

[Brian Willoughby]

On Jun 30, 2017, at 1:37 AM, Werner Flügel <werner.fluegel at b-tu.de> wrote:
> Am 29.06.2017 um 22:26 schrieb Tom Wiltshire:
>> Aaah!!! Yeah, I thought I remembered the name, but I couldn't think from where! 
> Hi,
> maybe from electro-music forum:
> 
> http://electro-music.com/forum/topic-59007.html
> and
> http://electro-music.com/forum/topic-30118.html
> 
> WF

Very interesting. I looked at the DIVIDERS.png section of the schematic, and it seems that half the notes are rather flat.

6 of the notes, A, Bb, D, Eb, F, and Gb are between -5.45% and +8.09% of the A440 standard. That's pretty good, and seemingly standard.

The remaining 6 notes, Ab, B, C, Db, E, and G, are way flat. They range from 21.5% flat to 43.5% flat.

All that it would take to fix those 6 flat notes is to increase the terminal counter value by 1.

I haven't read the entire E-M forum threads, but did the designer ever figure out that there are/were tuning problems and correct them?

Brian


p.s. Seems like the CD4040 could run a bit higher than 2 MHz to get more pitch accuracy for equal temperament, since the counter is wider than what's being used. I doubt that 16 MHz would work, even with a 15V supply, but 8 MHz should work. That would give a couple more bits of precision.