If you had shrill tone that you had terribly P90s.
Quite possibly there wasn't anything terrible about the original P90 in my SG. It just didn't have what I needed to play hard rock, more AC/DC than Mountain ;-)
This is back in the day when an SG Jr. didn't have any collectibility and just about just got you laughed at... a lot of other guys with similar guitar LP Jr's and Specials not only had gnarly humbuckers in them but also Khalers just to keep up with the times, play Eruption, etc...
I've never been able to like P90's like some people can, it's a freq resonance thing.
I'm kind of a devotee of the LP standard into a Marshall JMP sound, a sound that very much requires a PAF
maybe because of this.
"The resonant frequency of most available pickups in combination with normal guitar cables lies between 2,000 and 5,000 Hz. This is the range where the human ear has its highest sensitivity. A quick subjective correlation of frequency to sound is that at 2,000 Hz the sound is warm and mellow, at 3,000 Hz brilliant or present, at 4,000 Hz piercing, and at 5,000 Hz or more brittle and thin. The sound also depends on the height of the peak, of course. A high peak produces a powerful, characteristic sound; a low peak produces a weaker sound, especially with solid body guitars that have no acoustic body resonance. The height of the peak of most available pickups ranges between 1 and 4 (0 to 12 dB), it is dependent on the magnetic material in the coil, on the external resistive load , and on the metal case (without casing it is higher; many guitarists prefer this). The resonant frequency depends on both the inductance L (with most available pickups, between 1 and 10 Henries) and the capacitance C. C is the sum of the winding capacitance of the coil (usually about 80 - 200 pF) and the cable capacitance (about 300 - 1,000 pF). Since different guitar cables have different amounts of capacitance, it is clear that using different guitar cables with an unbuffered pickup will change the resonant frequency and hence the overall sound.
Up to this point, it has not taken into account the influence of eddy currents in metal parts. Such currents appear wherever an alternating magnetic field flows through electrically conductive parts. These parts are mostly the cores of magnetic coils – that is, either permanent magnets (in which the currents are relatively weak) or soft iron parts such as screws or fixed slugs (where the currents are stronger). Strong eddy currents can also occur in metal covers; these currents vanish when the covers are removed."