independed clean control

[rocket88]

so i got to thinking today about ways of adding back your clean signal to a fuzz/od/distortion pedal. typically i've always used a traditional blend, the split n' blend to be exact, and as good as it is i've always been annoyed at how it works. since it takes away from your affected signal to add in some of your unaffected signal there by loosing output, and not allowing your clean signal to go above unity. what i really want is an independent clean control that can have the clean a 0 to being boosted to match the distorted signal, without effecting the level of the distorted signal.

not after some research i came across something that peaked my interest. taking a look at the sparkle drive



the signal is split in front of the distortion and is boosted by the 2 amp in the dual opamp. now taking a look at the rat



you see that it's basically the same effect, but without the clean boost from the 2nd opamp, since it uses a single opamp instead of a dual.

now here's my thought and question, can the clean boost section be removed from the sparkle drive and implemented in other pedals, for instance like the rat? now i've also been thinking is how to take the split n' blend have it set at a predetermined blend amount, and add a boost to the clean line with the clean boost pot external.

so thoughts?

[Frank_NH]

I think it would work, but I would add an adjustable gain to the clean side as a pot in the feedback loop of the op amp.  You would need that so as to ensure that the signal level from the clean and overdrive sides were equal at the blend pot.  Then, blending all clean or all overdrive would yield the same output level.

There's also the Klon double-gang pot solution...

[induction]

Conceptually there is not very much difference between the Sparkle Drive approach and the Split 'n' Blend. The only major difference is that the Sparkle Drive buffers the clean path with a non-inverting op-amp and the Split 'n' Blend uses a jfet buffer. This difference is important because an op-amp allows you to add gain while maintaining the buffering, while turning a jfet from a buffer to a booster will change the impedances.

The gain on the Sparkle Drive is not adjustable, but it would be very simple to add either a gain control or a post-gain volume control to the clean path independent of the blend, and of course you can do this with either a pre-set or a variable blend.

This approach relies on a buffering the input and output of the dirty effect (if that effect doesn't already have input and output buffers, you may want to add them, or at least the output buffer). So it should work fine with any circuit follows the usual rules of pedals: high input impedance and low output impedance. Any pedal doesn't sound good with an input or output buffer may not work out so well.

You might get away with skipping the input buffer on the dirty side, since adding an op-amp buffer in parallel to the naked input of the circuit shouldn't cause too many problems. I haven't tried it, though. So trust your breadboard more than me.