Um... is there an easy way to get 5 octaves up?

[R.G.]

>I'm just trying to keep Alex busy.

I understand. That's what the smilies were about.   

Surely we can tolerate several cents error? Only 0.3% or so absolute error.

I certainly can.  But musicians and listeners exist for which a cent of error is grating.  And I was also trying to give Alex things to think about while he was busy.

The current-sources may be easily trimmed to accommodate +/-10% caps.

Yep, I agree. That brings in trimming and drift issues.   

Then there's drift. 32X _is_ a large ratio. 0.3% is a tight error budget. Two caps or two current-sources 32X different are not likely to drift together.

Yep.

Alex - consider this all to be part of the list of gotchas that can get into this kind of thing when you're messing with a digital system (the human brain's perception of octaves and harmonics) with an inherently analog approach.  The error budget starts tight, and keeps you fighting the whole time. The reason that active lockup with a PLL and digital techniques work better is that they directly address the analog error and drift issues up front, instead of always fighting them as secondary separate issues.

[stringsthings]

... I recall the first modular synths using absurdly expensive or fancy-connected chips and discrete comparators to keep pitch error low. (ARP used a chip cost as much as a week's supply of beer.) ...

from the book, "Vintage Synthesizers" by Mark Vail:

From its inception, ARP was on the cutting edge of technology, and by the mid -70's it enjoyed preeminnence in the marketplace.  It had 40% of the $25 million [synthesizer] market, surpassing Moog Music ... But by 1981, Pearlman's Lexington, Massachusetts, company was dead, the victim of miscalculation and the worst form of mismanagement; no management at all.

perhaps they needed more differential equations in their diet ? 

i did get the chance to see a used Avatar in a music store back in the day .... it wasn't in the best of shape, but it was interesting nonetheless ...

[earthtonesaudio]

>I'm just trying to keep Alex busy.

And I was also trying to give Alex things to think about while he was busy. 

Thanks guys.  There's enough here to keep me busy for quite some time.