[sdiy] TH XR2206 VCO tune pot

[Derek Holzer]

I've been building several of the very XR2206 VCOs designed by Thomas 
Henry, with a PCB layout by Tom Bugs:

http://www.bugbrand.co.uk/docs/TH_XR2206VCO_BugPCB.PDF

However, I find that the main tuning pot seems more than a bit too wide.

The bottom third is subsonic, the middle third is within hearing range 
and the upper third is ultrasonic. The fine tune, on the other hand, is 
quite subtle--as it should be. But I'd prefer that most of the main pot 
was audible, so what can I do?

One thing I noticed is that the fine tune pot has a 3M3 resistor after 
it (R46), while all the other inputs have 100K. If I wanted to reduce 
the range of the main tune pot, I could increase the value of the 
resistor after that pot (R28), right?

So rather than trial and error, is there any predictable way to find a 
good range? How would that be calculated? Is it a linear thing, where 
twice the value (i.e. 200K) would give me half the range (which would be 
fine with me)? Or is it more complicated than that?

Thx+best!
Derek

-- 
::: derek holzer ::: http://blog.myspace.com/macumbista ::: 
http://www.vimeo.com/macumbista :::
---Oblique Strategy # 59:
"Don't avoid what is easy"