5Y3

The 5Y3 is a medium-power directly-heated rectifier vacuum tube introduced by RCA in 1935. It has found wide use in tube radios and early guitar amplifiers (of the Fender Champ type.) It is virtually identical, electrically, to the 4-pin type 80 tube, but with an octal base.
The success of the 80 and 5Y3 led to the development of many similar rectifier tubes of both higher and lower power ratings, including the 5V3, 5W3, 5X3, 5Z3, 5U4, and 5Z4. The epitome might have been the 3DG4 of the 1960s, with a full 240 milliamp capability.
Currently, a plug-in replacement is being manufactured by Sovtek in Russia, which is has very similar specifications, but is indirectly-heated, and can support currents up to 144 mA, versus the 120 mA of the original. However the Sovtek 5Y3 is not a true 5Y3. It drops less voltage than vintage 5Y3's, and may cause voltages to run too high.

From Wikipedia, the free encyclopedia

300B

The 300B is a directly heated power triode using a four pin base, introduced by Western Electric in 1937 to amplify telephone signals. It measures 6.4 inches high and 2.4 inches wide. It has a 40 watt anode dissipation. In the 1980s the 300B was rediscovered by audiophiles for use in home audio equipment and is known for its high fidelity, low noise and reliability. It is frequently used in single-ended triode (SET) audio amplifiers such as the Cary CAD-1610-SE and the Cayin A-300B.
Due to their rarity and high demand, new old stock (NOS) 300B tubes made by Western Electric from the 1940s–1960s have become collectible items among audio enthusiasts, with price tags in excess of $700 and used tubes selling for over $400.
Current manufacturers of new 300B tubes, and various workalikes include Electro Harmonix, Emission Labs, JJ Electronic, KR Audio, Sophia Electric, Sovtek, Svetlana and Westrex Corporation (which produces a "recreation" of the original Western Electric tube[1]). Prices range from $175 to $900 per matched pair.

From Wikipedia, the free encyclopedia