Jazz Bass Master Blend — Complete Wiring
WIRING SIDE (back of control plate)
Blend / Volume / Q · Series/Parallel · Ring-hot phantom buffer
Passive tip + buffered ring — phantom powered
CONTROL PLATE — WIRING SIDE (back view, left/right mirrored from player view)
NECK
BRIDGE
BLEND
Bourns 250K MN · dual-gang
GANG A
1
NECK
2
WPR
3
GND
GANG B
4
GND
5
WPR
6
BRIDGE
VOLUME
CTS 500K log · push-pull DPDT
1
GND
2
WPR
3
IN
Q
CTS 50K rev-log · rheostat
1
COLD
2
WPR
3
IN
DPDT SWITCH
(on volume pot shaft)
POLE 1
POLE 2
1
PAR GND
2
NCK GND
3
SER BRG
4
6.8nF
5
Q WPR
6
22nF
6.8nF
parallel
22nF
series
RING-HOT BUFFER
2N5457 → 2N3904 · phantom powered (18V studio / 9V jam)
IN
GND
RING
OUTPUT
Switchcraft 12B TRS
TIP
passive
RING
buffered
SLV
BLEND OUT
wipers tied
SIGNAL NODE
tip · buffer · Q
GROUND BUS — all pot casings
A3→GND
B4→GND
V1→GND
NECK HOT
BRG HOT
A2 wpr
B5 wpr
BLEND OUT → Vol Lug 3
Vol wiper → SIGNAL node
SIG → Q IN
SIG → buffer IN
SIG → Jack TIP (passive, always)
SW1 → GND bus
NECK GND
SW2 common = neck ground (switched)
SW3 → bridge-hot tee (stacks coils in series)
Q1↔Q2 (rheostat)
Q wiper → Pole 2 common
SW4 → 6.8nF
SW6 → 22nF
6.8nF → GND
22nF → GND
buffer GND → bus
buffer RING → Jack RING (carries DC down, audio up)
Jack SLEEVE → GND bus
BRG GND
+ pickup shields
PICKUPS → BLEND → VOLUME → SIGNAL NODE → { TIP (passive, always) · BUFFER → RING (phantom) · Q-FILTER }
RING-HOT OUTPUT
TIP = passive direct, ALWAYS (plain TS cable = stock bass).
RING = buffered out + phantom power in (18V studio / 9V jam).
SLEEVE = ground. Buffer: 2N5457 → 2N3904, half-rail bias.
Tip and ring are independent — the cable chooses the path.
Q-FILTER (no tone control)
50K rev-log as series rheostat → mode cap → ground.
Parallel + 6.8nF: +6.9 dB @ 1165 Hz growl peak.
Series + 22nF: dark, treble rolloff (no boost).
A dial, not a switch: flat at 50K, full boost toward 2K.
PUSH-PULL (on volume)
DOWN = Parallel coils + 6.8nF (classic J).
UP = Series coils + 22nF (fat, dark, P-territory).
Pole 1 swaps coils, Pole 2 swaps the Q cap — one move.
Series mode: blend acts as a balance/tilt, not a free mix.
Ground bus (pot casings)
Ground connections
Signal path (blend→vol→node)
Pickup hot leads (dashed)
DPDT coils + switched neck gnd
Q-filter cap wiring
Buffered ring (phantom)
Wiper / junction