Electro Harmonix 12DW7EH Buis

Two different triodes in one bottle

Most twin triodes hold two identical sections. The 12DW7 does not: one half is a high-mu triode equivalent to a 12AX7, the other a medium-mu triode equivalent to a 12AU7. Circuit designers use that asymmetry deliberately — the high-gain half provides the amplification, the lower-gain half handles driving or phase-inverting duty, and both jobs are done by a single tube in a single socket.

Where you will meet it

Because of that split personality the 12DW7 is specified in particular amplifier designs rather than used as a general-purpose preamp tube, and it is worth checking your amplifier's tube chart before substituting anything else into its socket. The type is also catalogued as the ECC832 or 7247.

Current production

Electro-Harmonix builds this tube as a new design in Russia, with the consistency that comes from current production rather than old stock. It uses a 9-pin noval base. This item is a single tube.