[sdiy] TH XR2206 VCO tune pot

[Tom Bugs]

Yep - try changing it to 4M7 (I like it at 3M3 but I hear what you're 
saying)
xb

Derek Holzer 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.
>
> D.
>
> Scott Gravenhorst wrote:
>> Derek Holzer <derek at umatic.nl> wrote:
>>> Hi Scott,
>>>
>>> thanks for your reply. I did think of this, but since the range of 
>>> another pot in the schemo is restricted by following it with a 
>>> larger resistor, rather than putting resistors between V+/V- and the 
>>> pot, I thought that I would try to understand how that worked.
>>>
>>> best!
>>> Derek
>>
>> I can understand how that could modify one end of the range, but not 
>> both.  I'll be interested to
>> hear how that works.
>>
>>> Scott Gravenhorst wrote:
>>>
>>>> You can restrict the range of the pot this way:
>>>>
>>>>      v+
>>>>      |
>>>>      |
>>>>      Ra
>>>>      |                                                 
>>>> |                                            P
>>>>      O<----- ...
>>>>      T
>>>>      |
>>>>      |
>>>>      Rb
>>>>      |
>>>>      |                                       V-    
>>>> Where POT is the original tuning pot and Ra and Rb are resistors 
>>>> you will add.  The
>>>> values of these resistors will have to be trimmed or calculated by 
>>>> you.  If Ra and Rb
>>>> are the same resistance as the pot, then the new range will begin 
>>>> at about a third of
>>>> where it was without Ra and Rb and it will end about 1/3 before it 
>>>> gets to the end.  I
>>>> can't guess what frequencies this will give...  Ra and Rb can also 
>>>> be trimmers so that
>>>> you can adjust the exact range you get.
>>> -- 
>>> ::: derek holzer ::: http://blog.myspace.com/macumbista ::: 
>>> http://www.vimeo.com/macumbista :::
>>> ---Oblique Strategy # 101:
>>> "It is simply a matter of work"
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>>>
>>
>> -- ScottG
>> ________________________________________________________________________
>> -- Scott Gravenhorst
>> -- FPGA MIDI Synthesizer Information: home1.gte.net/res0658s/FPGA_synth/
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