This is not a replacement for the existing PS-21, but is a brother tube power supply (note the B in 'PS-21B"). Just like the PS-21, the new PS-21B holds three independent regulated power supplies: one high-voltage and two low-voltage regulators. (Note the three heatsinks.) Unlike the PS-21, the PS-21B uses a voltage-doubler-rectifier circuit for the low-voltage regulators. Why? Answer: 6.3Vac secondaries. $119.00 | New PS-25 Bipolar Power Supply
I have needed something like the new PS-25 for a long time. The PS-25 is a low-voltage, bipolar, voltage-regulated power-supply that is powered by a single secondary AC voltage, such as a 12Vac wallwart transformer or a regular power transformer secondary winding. $39.00 |