Aikido and Tetra Phono-Stage PCBs and Kits

Phono Preamps
Despite predictions to the contrary, spinning black vinyl by the warm glow of vacuum tubes persists. In spite of the popularly-held belief that both LPs and tubes are dead, long dead—most believe that the vacuum tube died about 50 years ago and that the LP record died 25 years ago at the birth of the CD—both tubes and LPs grow more popular with each coming day. Tubes refuse to fade to black and solid-state audio gear is still embarrassingly being advertised as sounding tube-like; and Marantz once again sells turntables and new records are pressed daily.

Adding the Aikido topology to a phono preamp makes perfect sense. The Aikido’s low distortion, noise, and output impedance, without the use of negative feedback—all are desirable attributes in a phono preamp.

The Tetra phono stage combines the Aikido-All-in-One's power supply with the CCDA topology, a combination that allows an excellent tube phono stage to be made easily and inexpensively. The Tetra uses only four tubes, not the eight tubes that the Aikido phono stage requires. And it holds two power supplies, one for the high-voltage B+ and a low-voltage regulated power supply for the heaters. The high-voltage power supply is unregulated, but uses cascading RC filters to smooth away ripple. Of course, the power supplies require an external power transformer(s) with two secondary windings, one high voltage for the B+ voltage and one low-voltage for the heaters.

Tetra Sans PS & User Guide
The Tetra Sans PS phono stage uses two tube-based gain stages with a passive equalization network in between. The gain stage's topology is the Constant-Current-Draw Amplifier [CCDA], whose low distortion, fairly high gain, and low output impedance are desirable attributes in a phono preamp. The CCDA is a compound circuit that holds a grounded-cathode amplifier directly cascaded into a cathode follower. So what; what's so special about this obvious pairing? Its special status lies in the details.
The Aikido PH-1 phono stage returns. Building phono stage based on the Aikido topology makes perfect sense, as the Aikido’s low distortion, noise, and output impedance, without the use of negative feedback—all are highly desirable attributes in a phono preamp. The Aikido PH-1 phono preamp is an extremely flexible design, as a nearly infinite number of different Aikido Phono Stage configurations can be built on the PCB. Nonetheless, our goals always remain constant: high-gain, low-noise, and low output impedance. The input tubes provide the voltage gain in this preamp, while the output tubes isolate the input tubes from both the equalization network and the external load, and they deliver a low output impedance.