Post by ijustwannastrat on Oct 13, 2010 8:59:40 GMT -5
I remember posting this already, but it's not here, so here we go again....
How would you go about wiring a passive EQ onto a guitar? The way I figure, if a cap and a pot can make a treble reducer, why can't you make a knob for bass and mid reduction? Or am I not fully understanding how a tone knob works?
The tone knob works because the capacitor dumps all the treble frequancies to the grounding of the guitar, (ie; the frequancy has a negative corelation with impedance)
You MIGHT be able to get a variable bass cut by using an inductor to ground, as an inductor has a direct correlation breween frequancy and impedance (lets bass frequancies through to ground, but blocks the treble) Mid control? maybe an inductor in parallel or series with a cap??
We've discussed the possibility of bass/treble/mid controls before. However, realize that since we can't boost mids in a passive scheme, all that can really be achieved passively is a sort-of bandpass filter effect, which would roll off the highs and lows simultaneously, leaving the mids (sort of). How effective this would be is open to question.
Ozboomer's "Simplemod" (apparently not so simple since it's now one of the longest threads on the board! ;D ;D) has both treble and bass rolloff pots, and I think he toyed with a mid-pass one at one point as well.
A while back, I posted this Framus, with a Schaller designed tone circuit from the '50s:
That uses a fixed switch rather than pots, so the settings aren't variable. But I suspect you could use that sort of a set up with pots instead. One problem is interaction of the pots, and loading of the circuit. By having both bass and treble controls in the circuit at the same time, they will affect each other to a degree.
A separate "mid" control would not really be needed since the effect would be the same as turning down both the bass and treble controls. And 3 pots in parallel will compound the interaction problems.
But if one truly wanted to try to have all three pots, bass, mid, treble, I would try a scheme where the "treble" pot was wired as per the diagram above (i.e., it's really a bass cut), the bass pot is a standard tone control (i.e., cuts the treble, leaves the bass in), and the mid would be a dual gang pot with one half wired like the treble control and the other half like the bass control. In theory, the mid knob would then give you a single knob to turn to get a bandpass or "gate" effect on the mids. But, again, theory and practice may be 2 very different things here.