[sdiy] VCO that goes SHARP in highest octaves??

[Neil Harper]

On 6/17/22 14:04, Ian Fritz wrote:
> Something else you might try: reduce the values of the integrating cap and the reference current by a factor of two or so. This could possibly reveal any self-heating in the expo transistors.
>
> Ian

We have a winner!

Reducing the integrator cap and reference voltage by a factor of 2 as
Ian suggested now has the VCO working as expected.

(cents)	C4	C5	C6	C7	C8
BEFORE	0	0	0	+5	+13
AFTER	0	0	-1	-2	-4


The flat higher octaves were easily trimmed out with a very small amount
of added HF-Trim exactly as expected.


I haven't tried Phil Macphail's suggestion yet though of adding a
resistor between the expo pair and the 13700's Iabc pin. Is there an
advantage to either solution?


--
/// Neil Harper
/// Every Wave is New Until it Breaks