They may have come with 4X125As , but the 4CX250Bs work fine. True AB1 with choice of 50 ohm resistive inputs or tuned input network. 2 to 3 watts in would get 750 watts out. I had to put a resistive pad in front of mine to keep from overdriving it with 20 watts. Tough old amp to be almost 50 years old. Don WA4NPL