Hello, I picked up a Henry 2K 4 amplifier it uses 2 glass tubes believe to be 3- 500's Looks clean and in good shape. What are they. selling for? May 29, 2009. This linear amplifier was made on. 60's by Henry Radio in USA. It's very heavy unit console due to the heavy duty transformer. It uses 2 tubes Sep 27, 2013 If you have additional information on Henry RF amplifiers. which you would like to share with others, Henry Radio; 2K-4 Amplifier; May 1974.