[sdiy] TH XR2206 VCO tune pot

[Derek Holzer]

That's the kind of explanation I was hoping for! Thanks Scott!

D.

Scott Gravenhorst wrote:
> Derek Holzer <derek at umatic.nl> wrote:
>> If you look at the schematic:
>>
>> http://www.bugbrand.co.uk/docs/TH_XR2206VCO_BugPCB.PDF
>>
>> You'll see that the fine tune and main tune are essentially the same: 
>> 100K pots between V+ and V-. The only difference is that the wiper of 
>> the fine tune goes through a 3M3 resistor, and the main tune goes 
>> through a 100K. They are both summed after that. That's the part I'm 
>> trying to understand.
> 
> The two inputs are summed by IC2B, so it's a simple summing circuit to consider. 
> Increasing R28 will limit the current that can flow through it.  If, for example, you
> double R28, you will limit the maximum current delivered to the summing node of IC2B
> by the TUNE pot.  This will reduce the top end of the range, but not the bottom, so
> the subsonic part of the range will still be there. 


-- 
::: derek holzer ::: http://blog.myspace.com/macumbista ::: 
http://www.vimeo.com/macumbista :::
---Oblique Strategy # 81:
"Go to an extreme, move back to a more comfortable place"