This is a minor new revision of the old stereo noval PCB, bringing it to Rev. F. The PCB color is now red, but the real difference is found in three major changes: each channel's B+ RC filter is made up of pure polypropylene (no electrolytic) capacitance and each channel requires its own separate heater power supply and the output can be configured in Aikido push-pull to drive high-impedance headphones.
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 PCB requires a power supply that offers a high-voltage B+ voltage and two low-voltage, independent power supplies for each channel's heaters. The best choice is the PS-21, as it is the same width as the new Aikido noval, so it can be placed right up against the new board. In addition, the PS-21 holds two low-voltage regulators for the heaters and one high-voltage regulator of the B+ voltage.
The price we must pay for sporting two heater power supplies, other than having to provide two regulated heater power supplies, is that we become more limited in possible tube selection. For example, we could use a 6CG7 as the input tube and a 6DJ8 or 6H30 as the output tube, but then we must use a 6.3Vdc heater power supply, as we cannot place the two heaters in series, due to each tube type drawing a different amount of current. On the other hand, we can use two identical 6.3V tubes, say two 6CG7 or two 6DJ8 or two 6AQ8 tubes and place the heaters in series and use a 12.6Vdc heater power supply. In my test build, I used a 12AU7 as the input tube and an ECC99 as the output tube, a fine-sounding combination by the way, with a regulated 12Vdc heater power supply per channel. The major stipulation is that the two triodes within the envelope be similar and that the tube conforms to the 9A or 9AJ base pin-out. Sadly, the 12B4 and 5687 cannot be used with this PCB.
The Aikido noval stereo 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 6 by 6.5 inches, with six mounting holes, which helps to prevent excessive PCB bending while inserting and pulling tubes from their sockets.
This latest Aikido PCB does retain a few small features from the older PCBs, such as the two output coupling capacitors (which I deem essential). Line stages, single-ended power amplifier front-ends, tube-based mixers, I-to-V converters—all are possible with this Aikido PCB.
PCB includes 16-page user guide with schematics and instructions.