PX66 – Card for Extra Power Tubes with Components

CAD $46.00CAD $124.00



PX66 allows the addition of of additional pairs of output tubes to our PA66 series of power amp kits for more power, fuller tone, or both. PX66 includes the PCB, tube sockets, meter jacks, and all components that mount on the PCB.

  • accepts any standard-pinout octal
  • 6L6, 6V6, EL-34, 5881, 6550, KT-66/77/88
  • individual bias adjustments
  • ceramic tube sockets
  • metal-film and flameproof resistors
  • polypropylene and long-life electrolytic capacitors
  • meter jacks
  • fixed or cathode biasing

PX66 accommodates all of the flexible wiring options of the PA66 Octal Power Tube Amp:

  • triode-pentode switching
  • ultralinear wiring
  • switchable fixed or cathode bias
  • separate heater wiring allows use of #22 wire

When used with PA66, PX66 allows consistent power tube spacing for proper ventilation of high-power tubes and amplifiers.

Want to build 100W? 160W? 200W? Add a single PX66 to PA66.

Want to build a monster bass amp of 300W? 400W? 500W? Just add more PX66s. Note that powers up to 450W are accommodated by six power tubes, using 6550 or KT-88.

Or, do you just want the tonal flexibility of more tubes without a power increase, just like the Plexi and 800 projects in our book The Ultimate Tone Vol.3 (TUT3)? Or like the Standard in our book TUT5? PA66 and PX66 accommodate whatever you want to do.

PX66 can be used on its own as the heart of a fixed-ratio Super Scalar, as TUT5 illustrates.

PX66 is easy to assemble. Everything mounts on the high-quality printed circuit board, except for the meter jacks.

Switching between fixed-bias and cathode-bias operation can be “global” (both tubes) or independent. Independent bias switching allows one tube to be operated with fixed-bias while the other is cathode biased. Manual switches (not supplied) can be used, or relays. PA66-CR is a kit of the relays, and its use greatly simplifies the switching.  The relays mount directly on the PA66 board.

PX66 is the perfect complement to PA66.

Available configurations:

Standard DIY Kit (PX66-COMP) – includes the PCB, kit notes, meter jacks and all passive components that mount on the PCB.
PCB + Hard-to-find Parts (PX66-HP) – includes tube sockets, pots, and meter jacks.
PCB Only (PX66-PCB) – just the PCB and kit notes.

PCB size: 5.25 x 3″ 134 x 76mm