[sdiy] 1.0 kohm "tempco" for VCO / sub octave question

[Thomas Dunker]

On Mon, 1 Mar 2004, Oren Leavitt wrote:

> 1) You can get away with using an ordinary 1K 1% resistor in place of the
> tempco if your use for the VCO doesn't require precise tracking -
> especially if you're using just one VCO in your synth.

 The thought did cross my mind...

> 2) You can get the PT-146 at:
> http://www.precisionresistor.com
> Just request a quote and they'll email you a price.
> The PT-146 was USD 7.50 each the last time I ordered a small batch in October 2003.

 Sure, but I'll just be needing a couple of them, so postage, customs fees
and taxes would make the cost multiply by a ridiculous amount. I therefore
would prefer to use something I can obtain from my regular supplier.
 Rene's kludge scheme for the KTY81-120 looks like something I can happily
use.

> For the JFET - The 2SK... devices will probably work fine with Ray's VCO.

 Good.

> For sub-octaves, a 4013 dual flip-flop will give you the two sub octaves
> with one chip. Feed it directly from the output of the pulse comparator
> thru a diode to cut off the negative half of the signal so that it is
> within the 0 to V+ range of the CMOS.

 Sounds simple enough to me. I might want to add a separate second sub
generator along the same lines to enable me to make more complex signals
from external square/pulse generators.

Thanks a lot for the ideas!

Thomas