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Gibson SB Bass Circuit Information

Gibson bass guitars | SB bass wiring

The circuitry of the Gibson SB series bass guitars were typically simple, and plate-mounted rather than body mounted (to allow remote assembly). Both series controls were effectively the same: two switches (an on/off for each pickup), and a master tone and volume control.

Gibson SB-300 bass, Gibson SB-400 bass

1971 Gibson SB-400 bass circuit photograph Gibson SB-300 / SB-400 bass and SG-200 / SG-250 / ES-320 circuit diagram (simplified) Gibson SB-300 / SB-400 bass and SG-200 / SG-250 / ES-320 circuit schematic

The controls and associated circuitry of the Gibson SB bass guitar series were quite simple. A master volume and tone, and two slide switches (on/off); one for each pickup. The pickups fitted to the SB-300 and SB-400 are Gibson single coil units, wired in series. The slide switches change the ground point by shorting across each pickup, selectively removing it from the circuit.

Both circuitry and pickups were identical to those of the SG-200, SG-250 and ES-320 six string guitars; one way in which the manufacturing cost of these guitars and basses was reduced.

Gibson part numbers from the 1971 part list are as follows:

  • Part #13570 Pickup assembly
  • Part #70024 Volume and tone pots*
  • Part #19231 Tone Control Knob
  • Part #19232 Volume Control Knob
  • Part #70486 Switch
  • Part #70251 Output jack

* Interestingly enough, many instruments (predominantly early examples?) including this 1971 SB-400 do not use part number 70024 (which are 500k pots), but part BA811-3701 (250k pots) with 1960s date codes. These are the same potentiometers that appeared in 1960s Kalamazoo KG guitars, no doubt old stock that was used up before part 70024 was introduced.



Gibson SB-350 bass, Gibson SB-450 bass

1973 Gibson SB-450 bass circuit photograph Gibson SB-350 / SB-450 bass circuit schematic

The circuitry for the second series SB basses (SB-350 / SB-450) is fairly similar to the earlier SB instruments: still a master volume and tone control, and an on/off switch for each pickup, and the output jack, all mounted on a simple control plate attached to the front of the bass. - though with a slightly different arrangement, a 250kΩ rather than 250kΩ tone pot (part 70021), and a slightly smaller value capacitor. Pickups are now Gibson SB humbuckers.

Gibson part numbers from the above schematic are as follows:

  • Part #70024 Volume pot
  • Part #70021 Tone pot
  • Part #19231 Tone Control Knob
  • Part #19232 Volume Control Knob
  • Part #70486 Switch
  • Part #70251 Output jack