Graph Tech Ghost - Manual (Page 13)

13
When the Hexpander is piggybacked on the Acousti-Phonic, the
mag-to-pin-7 harness is not necessary because Acousti-phonic
passes the acoustic and/or magnetic signals to the Hexpander.
But when you install the Hexpander only, adding the mag-to-
pin-7 harness and an acoustic volume control (250K or 500K
audio pot) provides this feature in the absence of the Acousti-
Phonic. Note that the acoustic sound with the mag-to-pin-7
harness is the raw acoustic sound, and not the true acoustic
sound that the Acousti-Phonic creates. If you want pin-7 to
carry just the mag or just the raw piezo signal, you can
leave the unused wires disconnected and coiled up.