Tube chart · Guitar amp

Tubes for Vox AC30 (Top Boost)

Era: 1959–presentPower: 30 W

The AC30 is the British clean-chime sound — 4× EL84 in pure class-A cathode bias, no negative feedback, GZ34 rectifier sag. Brian May, Tom Petty, The Edge. The Top Boost channel adds an extra 12AX7 stage and a separate treble/bass tone stack; EF86 channel pre-AC30/4 is rarer and prized for its dense, microphonic vintage character.

Complete tube line-up

Every socket in the AC30 (Top Boost), with stock tubes, direct-swap alternatives, and rolling notes. Tube names link to dedicated specification pages.

  • Normal channel + Top Boost × 3
    12AX712AX7 / ECC83
    Alt:ECC83
  • EF86 channel (early AC15/AC30)
    EF86EF86 / 6267
    Alt:6267
  • Power tubes (cathode bias, class A) × 4
    EL84EL84 / 6BQ5
    Alt:6BQ5
  • Rectifier
    GZ34GZ34 / 5AR4
    Alt:5AR4, solid-state (Korg-era)
Important: bias before you swap

Power tube swaps almost always require rebiasing — running a new quartet of EL84 cold or hot will shorten tube life dramatically and can damage the output transformer. See the biasing guide and the troubleshooting guide before rolling tubes.

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