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Re: Tapped Pot Source


 :
12/11/1999 12:57 AM
Rob W.
Re: Tapped Pot Source
Hello!  
 
Try out Smart Parts:  
 
http://www.partssmart.com/  
 
The reissue '63 Vibroverb uses 250K/50K tap Treble pot that is a current production part...  
 
Just F.Y.I.  
Rob W. :-)  
 
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12/12/1999 8:16 AM
Steve A.

Rob:  
 
    I believe that Bruce Collins and/or Randall Aiken had posted revised values previously to use with the 250k/50k reissue pot (the original was 350k/70k). Can someone repost that? (The changes were a lot more drastic than I would have thought...)  
 
Steve Ahola
 
12/12/1999 9:18 AM
Randall Aiken

That was me, but I didn't save the post. I simply used the impedance scaling formulas available in the paper on my website entitled "Tone control scaling". I scaled all impedances by the 250k/350k impedance scaling factor (ZSF = 0.714). The new values are obtained by the following formulas:  
 
R' = R*ZSF  
L' = L*ZSF  
C' = C/ZSF  
 
If nobody archived that post, I'll recalculate the values if needed, but it should be fairly straightforward with the above formulas.  
 
Randall Aiken  
 
12/12/1999 6:39 PM
Rob W.

Hello!!  
 
I was the one who asked Randall that question a month or two ago and here is what he figured out...  
 
C1=350pF (not 250)  
C2=.14uF (not .1uF)  
C2=.07uF (not .5uF)  
C4=.007uF (not .005uF)  
Slope Resistor= 71.4K (not 100K)  
Bass Pot= 200K (not 250K)  
Mid Resistor= 4.9K (not 6.8K)  
 
Good Luck!!  
And if there are anymore questions about that post, I have a hard copy version that I can retype..  
 
Cheers!  
Rob W.  
 
12/12/1999 9:23 PM
Randall Aiken

Those were the calculated values, I had recommended standard values as well. I think they were:  
 
C1=350pF (100pF in parallel with 250pF)  
C2=0.15uF  
C2=0.068uF  
C4=0.0068uF (6800pF)  
Slope Resistor= 68k  
Bass Pot= 200K  
Mid Resistor= 4.7K  
 
Randall Aiken
 
12/14/1999 9:09 AM
Steve A.

Randall and Rob:  
 
    Thanks for the values as well as the formula!  
 
Steve Ahola
 

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