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previous: Steve B Does the Fulldrive 2 "boost" functi... -- 10/30/1999 1:27 AM View Thread

Re: FD 2 question...

10/31/1999 11:26 PM
Mark HammerRe: FD 2 question...
In many cases, it is possible to change the gain, and change the output volume level, with one jumper each. This means you can use a standard DPDT stompswitch (or toggle or slide switch) to thicken the sound and add more growl without upping the volume. I've seen a number of boutique pedals that incorporate this kind of feature. I've done this on homebrew distortions, and it's a nice feature.  
 
In principle, it involves changing a gain-setting resistor value (done by shunting one of two resistors in series or by sticking another one in parallel), and sticking another resistor in series with the input to the output volume control, although I'm sure there are probably other more complicated ways.  
 
The practical problem is really one of appropriate component selection for psychoacoustic matching. So, you can select a gain setting resistor value, and then select an output-reducing resistor value based on the amount of gain and amount of desired attenuation, but since the effect adds harmonic content (by design, of course) complementary gain increase and attenuation doesn't produce the same *perceived* loudness. Extra distortion means that the complementary attenuation needs to be just a bit more than you think to get perceived level matching, and that's often hard to do with stock components; and harder to do with 5% tolerance components. I know, because I tried doing it on my pedal, and with stock component values, I still couldn't get an exact loudness match. I live with what I have, and that's it.  
 
So, either one has to work all of this out in great detail in advance, or put trimpots on the board and adjust for matching. Alternatively, the switch can select between two sets of pots (which some units do).