The Aikido All-in-One octal stereo PCB contains two Aikido gain stages and both the high-voltage and heater power supplies.
Aikido Octal Stereo All-in-One is a major new revision of the old Aikido stereo All-in-One PCB. The PCB color is now red, but the real difference is found in one major change: each channel's B+ RC filter is made up of pure polypropylene (no electrolytic) capacitance. The red solder-mask merely marks these changes and looks quite snazzy by itself.
All that is needed to finish the entire line stage is a chassis, power supply, volume and input selector controls, and a handful of RCA jacks and hookup wire. Although this custom Aikido kit isn't all that is needed, it is a great start.
This FR-4 PCB is extra thick, 0.094 inches (inserting and pulling tubes from their sockets won’t bend or break this board), double-sided, with plated-through heavy 2oz copper traces. In addition, the PCB is lovingly and expensively made in the USA. The boards are 8.5 by 6 inches, with five mounting holes, which helps to prevent excessive PCB bending while inserting and pulling tubes from their sockets. The PCB holds two Aikido line-stage amplifiers; thus, one board is all that is needed for stereo unbalanced use (or one board for one channel of balanced amplification).
B+ and Heater Power Supplies On the All in One board, two power supplies reside, one for the high-voltage B+ for the tubes and a low-voltage power supply for the heaters. The high-voltage power supply uses two RC filters to smooth away ripple, while the low-voltage power supply uses an LDO voltage regulator to provide a stable and noise-free voltage output.
The Aikido All-in-One octal PCB requires a traditional tube power transformer to energize its two power supplies and heat the rectifier, which requires its own 5Vac winding. The 6.3Vac winding that feeds heater power supply must offer at least 3.6 times more current than the heaters will draw. For example, four 6SN7s will draw 0.6A @12.6v, so the heater power transformer must be able to sustain an AC 4.32A current draw. A high-voltage center-tapped secondary must be used and the its center-tap must be attached to CT eyelet. A good example is the Allied Electronics 6K56VG power transformer, which is perfect for powering four 6SN7 tubes.
Redundant Solder Pads
This board holds two sets of differently-spaced solder pads for each critical resistor, so that radial and axial resistors can easily be used (radial bulk-foil resistors and axial film resistors, for example). In addition, most capacitor locations find many redundant solder pads, so wildly differing-sized coupling capacitors can be placed neatly on the board, without excessively bending their leads.
The All in One PCB provides space for two sets of capacitors to decouple both Aikido gain stages from the B+ connection and each other. This arrangement allows a large-valued electrolytic capacitor and small-valued film capacitor to be used in parallel, while a series voltage-dropping resistor completes the RC filter. In place of the RC series resistor, an off-board choke can be used (one per channel).
The made in the USA PCB comes with 16-page user guide that holds schematic and design examples.