Tube Amps / Music Electronics
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|12/11/1999 12:57 AM|
||Re: Tapped Pot Source|
Try out Smart Parts:
The reissue '63 Vibroverb uses 250K/50K tap Treble pot that is a current production part...
|12/12/1999 8:16 AM|
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...)
|12/12/1999 9:18 AM|
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.
|12/12/1999 6:39 PM|
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)
And if there are anymore questions about that post, I have a hard copy version that I can retype..
|12/12/1999 9:23 PM|
Those were the calculated values, I had recommended standard values as well. I think they were:
C1=350pF (100pF in parallel with 250pF)
Slope Resistor= 68k
Bass Pot= 200K
Mid Resistor= 4.7K
|12/14/1999 9:09 AM|
Randall and Rob:
Thanks for the values as well as the formula!
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