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-2 phono stage is based on the Aikido topology, which 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. Our goals always remain constant: high-gain, low-noise, and low output impedance.