Overall, the circuit employed by Gibson from 1971 onwards was in improvement over the design from the 1960's. One such improvement was that the choke was entirely removed from the circuit in all but position 4. However, one negative some feel plague both the 60's and 70's design is that position 4 sounds awfully thin and nasal. This sound is contrary to how Gibson advertised position 4 as being a "midrange notch" (see 1970's advertisement from Gibson). A notch filter (by definition), is a filter that passes all frequencies except those in a stop band centered on a center frequency. For example, if Gibson wanted to achieve a midrange notch, they would have wanted to pass all frequencies, except those centered around 800 hz - 1 kHz. If they wanted a lower midrange notch, they would design the notch to be centered around 300 - 500 hz. None of the above should sound thin and nasal, as most report position 4 sounds.

 

With that in mind, we have provided 2 tweaks to the Gibson 1970's circuit:

 

1). We have provided a true midrange notch in position 4, centered around 800 hz. Our position 4 does NOT sound thin and nasal (hear sound samples below) and will be more useful.
 

2). We have added versatility by providing a variable passive overdrive for the neck pickup, engaged via a push-pull pot. The passive overdrive has been voiced to work specifically with a very hot Mudbucker style neck pickup.

 

Sound Samples - performed by Tony Senatore

Position 1 Neck Pickup -

Position 1 Neck Pickup with drums/guitar -

Position 4 Neck Pickup w/Choke -

Position 1 Neck PIckups w/Diode Clipping -

 

Features

 

CHOKE BYPASS MOD w/ TRUE MIDRANGE NOTCH IN POSITION 4 (STANDARD)

As is the case with the Gibson 1970's design , the choke/filter is only in the circuit when the rotary switch is dialed into position 4. There is absolutely no residual filtering in the other 3 positions. Furthermore, we have provided a true midrange notch in position 4, centered around 800 hz.. Our position 4 does NOT sound thin and nasal (hear sound samples below) and will be far more useful.

 

PASSIVE OVERDRIVE / FUZZ ENGAGED VIA PUSH-PULL POT (OPTIONAL)

We experimented extensively with many different combinations of diodes, and have the determined the best sounding combination of diodes voiced to work with mudbucker style pickup in the 30K range. We have these diodes configured to be antiparallel (connected in parallel but with their polarities reversed) to provide symmetrical clipping.

The clipping is engaged via a push/pull pot. When the P/P pot is in the "down" position, it functions as a normal tone pot that cuts treble as you roll the pot counterclockwise. However, when the P/P pot is in the "up" position, the pot functions as an overdrive control. When the pot is rotated fully clockwise (on 10) you get maximum overdrive.

 

Please note: the diode clipping is voiced specifically to work with a mudbucker style pickup in the 30K range, such as the Curtis Novak Mudbucker reproduction pickup.