The Blackbird’s all-tube circuitry has been specially designed to function with a variety of different tube types (12AX7, 12AY7, etc) allowing guitarists to tailor the pedal to their own specific playing style and fine-tune their guitar tone to the absolute nth degree. There are three 12AX7 tubes fitted in the Blackbird pedal as standard. The 12AX7 is a 9-pin miniature dual triode, that is, the glass envelope of each tube contains two amplifier sections. In V1 one amplifier section is the ‘Clean’ channel input stage (identical to the input stage of a Fender ‘Blackface’ amp) and the second section is the output cathode follower buffer, which is common to both the ‘Clean’ channel and the ‘Gain’ channel. In V2 both amplifier sections are the first two gain stages of the ‘Gain’ channel and in V3 both amplifier sections are gain stages three and four of the ‘Gain’ channel. This article discusses everything you need to know on swapping out the stock 12AX7 tubes for different 9-pin dual triode types to alter the gain, character, response and feel of the Blackbird pedal for your own playing style and tone.
The three stock 12AX7 tubes yield greatest tonal flexibility. With this tube configuration the ‘Creamy’ (red LED lit) and ‘Classic’ (Blue LED lit) modes are voiced quite differently to one another allowing the Blackbird to effortlessly cover a wide range of guitar sounds from warm, purring bluesy overdrive to devastatingly saturated rich distortion. This huge flexibility is especially useful in a recording studio session situation where you can totally rely on the Blackbird as your one-stop tone tool for creating a wide range of authentic tube guitar sounds and capture them directly to tape without needing to use a guitar amp.