New Aikido Cascode PCB
The Aikido Cascode amplifier is a compound circuit consisting of a cascode input stage amplifier and an Aikido cathode follower output stage buffer. In a nutshell, the cascode circuit offers two huge features: gain, lots of gain; and low, very low input capacitance; thus, it delivers high gain and wide bandwidth. The cascode amplifier offers high gain, but a dismal PSRR (power supply rejection ratio) and high output impedance. Fortunately, the Aikido cathode follower topology can undo the leaked power-supply noise, while presenting a low output impedance.
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.
Dual Coupling Capacitors
The boards hold two coupling capacitors, each finding its own 1M resistor to ground. Why? The idea here is that you can select (via a rotary switch) between C1 or C2 or both capacitors in parallel. Why again? One coupling capacitor can be Teflon and the other oil or polypropylene or bee’s wax or wet-slug tantalum…. As they used to sing in a candy bar commercial: “Sometimes you feel like a nut; sometimes you don't.”
Each type of capacitor has its virtues and failings. So use the one that best suits the music; for example, one type of coupling capacitors for old Frank Sinatra recordings and the other for Beethoven string quartets. Or the same flavor capacitor can fill both spots: one lower-valued capacitor would set a low-frequency cutoff of 80Hz for background or late night listening; the other higher-valued capacitor, 5Hz for full range listening. Or if you have found the perfect type of coupling capacitor, the two capacitors could be hardwired together on the PCBs via jumpers J8 and J9, one smaller one acting as a bypass capacitor for the lager coupling capacitor. n the other hand, each coupling capacitor can feed its own output, for example, one for low-frequency-limited satellites and one for subwoofers.
The Aikido Cascode PCB provides holds two sets of power-supply capacitors to decouple both Aikido cascode 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).
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 6 by 6 inches, with five mounting holes, which helps to prevent excessive PCB bending while inserting and pulling tubes from their sockets. Each PCB holds two Aikido Cascode amplifiers; thus, one board is all that is needed for stereo unbalanced use (or one board for one channel of balanced amplification. External B+ and heater power supplies are required to energize the PCB.
Includes 16-page user guide with schematics and instructions.