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Shape your guitar tone by swapping compatible power tubes, without stopping to adjust the bias manually. The THD Bi-Valve 30 is a hand-built, single-channel all-tube amplifier head with touch-sensitive response for studio sessions, recording and live performance.

Use the built-in Hot Plate attenuator to explore power tube saturation at more manageable volume levels. Adjust the tone and output to suit your playing, then add your effects through the series loop.

Designed by Andy Marshall, the Bi-Valve 30 brings tube-swapping flexibility and classic all-tube response to your rig. Make it the centre of your next recording setup or take it along for your next live set.

• Flexible power tubes: Supports compatible octal types including 6V6, 6L6, EL34, KT66, KT77, KT88 and 6550, subject to manufacturer recommendations.
• Automatic biasing: Swap compatible power tubes without manual rebiasing.
• Up to approximately 30 watts: Output depends on the power tube configuration.
• Power attenuation: The built-in THD Hot Plate helps you reach power tube saturation at lower volume levels.
• Hands-on tone shaping: Treble, Bass and Attitude controls, plus input sensitivity and output level adjustments, let you shape your sound.
• Tube protection: Individual power tube fuses have LED failure indicators.
• USA-built construction: Hand-wired in Seattle, with two 12AX7-family preamp tubes and a black finish.