[sdiy] VCO voltage summer question?

[Harry Bissell]

I'm not sure I understood the question...

I'd leave POT1 circuit the  way it is, and add a second
POT (same as POT1) but with R1 increased in value to maybe
2.2M ohm. This will make the second pot have much less
range.  You can change the value if needed...

I would avoid adding resistors to the ends of the pots
to limit the range. This will make the loading on the
wiper affect the linear operation of the pot.

H^) harry


----- Original Message -----
From: Mykolas <mikas.paukstis at gmail.com>
To: synth-diy at dropmix.xs4all.nl
Sent: Sun, 21 Nov 2010 11:43:01 -0500 (EST)
Subject: [sdiy] VCO voltage summer question?

Hi all,

I'm breadboarding this VCO:
http://www.analogas.uzrasai.lt/wp-content/uploads/2010/11/VCO_v1.jpg
Many thanks to Jarek Ziembicki.

I'd like to have a two pots for "tune" (drift in 5 volts) and "fine
tune" instead of R2 and R12 (drift in 1 volt) and change R6 to 100k
trimpot for seting initial frequency.

How to calculate R1 and R2?

Or http://www.analogas.uzrasai.lt/wp-content/uploads/2010/11/potres.jpg

A) should I change R1 and R2 to 100K and add 15k resistors to each end
of P1 (change P1 to 50k too)? and have 5V drift and add 180k resistors
to each end of R12 for 1V drift;

B) add 30k resistor to +8V end of P1 for 0-5V and 350k for R12 0-1V?

Many thanks.



-- 

Mykolas
+370 67626261
www.analogas.uzrasai.lt
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-- 
Harry Bissell & Nora Abdullah 4eva