MOTM

>Thanks for the update. On board 1, Q2 and Q3 are either 2 x 2SA733
>or 1 x 2SA1349. Neither seem easy to find.

You don't have to take that 2SA733 verbally. And decent pnp transistor with 
the right pinout will do.
No matched pair required. There is a trimpot to adjust the balance between 
the two expo outputs, because some of the OTA chips I tried had terrible 
matching. That trimpot will even out any transistor mismatch, too.

>(For those who wonder what U10 and U12 are, they're MC1496.
>Available from Mouser for 0.62 USD or Farnell for 1.39 EUR, take
>your pick.)

Right.

JH.