Electro Harmonix 12BH7EH Vakuumrør

A driver tube, not just a preamp tube

The 12BH7 looks like a familiar 9-pin twin triode, but it is built for a heavier job. Its 3.5 W dissipation per plate gives it far more current capability than a standard small-signal triode, which is exactly what a driver stage needs when it has to swing the grids of the output tubes cleanly. Its medium amplification factor keeps the stage controlled rather than gain-hungry.

Where it earns its place

Electro-Harmonix positions this as a superior driver tube for hi-fi use, and that is where the difference shows: an under-powered driver stage softens transients and limits how hard the output stage can be pushed before it loses composure. The 12BH7 also serves well in line stages and cathode-follower positions for the same reason.

Before you fit it

It uses a 9-pin noval base and goes into any circuit specified for the type. Electro-Harmonix tubes are new designs of consistent quality, and many amplifier manufacturers fit relabelled versions in their own products. This item is a single tube.