I have plans like this to update several basses. I have two Carvin Icons (5 n 6er) that came with GhostTech saddles and two magnetic pups. They had a proprietary preamp that sounded pretty good and had trim pots for each piezo saddle, but developed string to string gain issues (only in active) on the low and high strings. So, I played them both in passive.
My plan uses a Bartolini AGMBoo to sum and buffer the piezo and the blended mag signal (using either the NOLL passive blend pot or the NOLL Mix Pot -either come after coil switching). I have considered using a Noll mix pot to blend the mags, which is an active buffering preamp and offers a clean signal and an accurate proportional blend, but that adds two buffers and more $. Then the signal MAY go into a Noll, tone/tone stacked on-off push-pull (for on the fly tone add/subtract from either active or passive circuits without twisting the knobs, enabling a switch on-off preset tone) then into the preamps. The 5er gets Delano SBC 5HE/S-4 Quads and a John East Uni pre (5-knob) and the 6er gets Delano SBC/S dual coils and a Noll TCM 3p full parametric. Both have active/passive switching on the V/V (Noll) or V (East) knob. I have a layout (minus some new ideas) image for the 6er.
My plan uses a Bartolini AGMBoo to sum and buffer the piezo and the blended mag signal (using either the NOLL passive blend pot or the NOLL Mix Pot -either come after coil switching). I have considered using a Noll mix pot to blend the mags, which is an active buffering preamp and offers a clean signal and an accurate proportional blend, but that adds two buffers and more $. Then the signal MAY go into a Noll, tone/tone stacked on-off push-pull (for on the fly tone add/subtract from either active or passive circuits without twisting the knobs, enabling a switch on-off preset tone) then into the preamps. The 5er gets Delano SBC 5HE/S-4 Quads and a John East Uni pre (5-knob) and the 6er gets Delano SBC/S dual coils and a Noll TCM 3p full parametric. Both have active/passive switching on the V/V (Noll) or V (East) knob. I have a layout (minus some new ideas) image for the 6er.
