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previous: floydfan Yeah, it gets real bright, up till ... -- 7/26/2000 3:24 PM View Thread

Re: Voodoo lab OD

7/26/2000 4:09 PM
Cole
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Re: Voodoo lab OD
The reason for the VLOD's brightness/darkness is that when you change the gain (via the gain pot) you're also changing the breakpoint of the RC filter in the opamp loop. When the gain is set low (high resistance on the gain pot) the bass rolloff is low, below the range of the guitar. When the gain is set high (low resistance on the gain pot) the bass rolloff is high, in the 1.5kHz range, which explains the brightness. One way to change this would be to put the gain pot in the feedback loop (ala the Tubescreamer), changing the variable gain pot toa 2.2k resistor (or other low, fixed resistance value) to set the bass rolloff at a fixed point. The formula for calculating this is 1/(6.28*R*C), with R being the value of the resistor in M ohms and C the value of the cap in uF. For example, with a 2.2k resistor, the bass rolloff would be at 723Hz.  
 
If you move the gain pot around, then you can add the boost pot in series with it as you describe. Then the addition of the ST tone control may be more usuable as well.

 
Replies:
floydfan Thanks Cole, I see the boost pots a... -- 7/26/2000 4:55 PM