Gibson Console Grande circuit question

Eric Stumpf · Post by **Eric Stumpf** » 2 Oct 2002 12:00 pm

Today I had an opportunity to look at the "guts" of three different post-war vintage Gibson Console Grande steel guitars. I want to replicate the exact circuit these instruments used for the sake of a project I'm working on. I must say that I'm in the dark as far as the presence of that second tone control is concerned.....what was the purpose of this? It doesn't seem to affect the tone of these particular guitars at all but it must have served a noticeable function at one time when all the capacitors worked with the correct values. Speaking of capacitor values, what caps would be presently available that would be close to the originals? As far as the pots go, I noticed the volume AND the tone control immediately next to it are both 250K. I'm assuming the tone pot should be linear taper like on a Fender but I can't tell if this is the case and besides, aren't most tone pots 1 Meg linear taper? The second tone pot is a 500K and again I'm unsure if it's audio or linear taper. Man, what a can of worms! The desire on my part to duplicate all this stuff is to achieve the amazing tone swells (boo-wah effect) these Gibsons are capable of producing. I hate to say it....hotter than a Fender hands down (and I'm a Fender guy). Does anyone out there know what correct pots and caps I need?

Donny Hinson · Post by **Donny Hinson** » 4 Oct 2002 4:30 pm

Nobody else is bothering, so I'll give this one a shot.

Well, I never owned one of them old Gibsons, but I imagine that the tone circuit was similar to most still used today. It's called a "high-cut" circuit. Through the the capacitor, and regulated by the pot, it just funnels a portion of the high frequencies to ground, thereby attenuating them. The more highs you attenuate, the damper, or bassier, the sound got. [This type of circuit (called a "passive" circuit) can only reduce what's there...it can't add or boost anything. However, taking a part of the highs away, and then adding more volume to the remaining lows gives the effect of a bass boost.]

The typical values for the tone pot were usually 250k-500k, with a linear taper. The audio, or log-taper pot (meant to make a volume change more uniform throughout its travel) was unnecessary in tone circuits, since our ears don't respond to tone changes in the same way they do with volume changes. The stock caps were usually between .002uf and .02uf. The higher the value, the more highs would be cut. Soooo, to get a bigger "doo-wah" effect, I'd use a higher value cap. to get more of a change...somthing like a .05uf, or maybe even .1uf should give you what you're looking for.

As far as that "other" tone control goes, it might have been a treble control, designed to let some of the highs bypass that "high-cut" part of the tone circuit. This would give a slight "scoop" to sound...kinda like turning down the middle on an amp, and then turning up the highs. Someone with repair experience on this particular guitar may be able to help more. [This message was edited by Donny Hinson on 04 October 2002 at 05:33 PM.]