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.
Introducing the new ACF 12Vac PCB and part kits. The key advantage to the ACF 12Vac is that it can be operated from a lowly 12Vac wallwart power supply, yet develop a fairly high-voltage B+ for the triodes and power the heaters with clean DC voltage.