I am the owner of two custom made class A monoblock amplifiers that
operate in triode. The outputs are a pair of 6550 tubes for each unit.
These need to be replaced and I seek your advice.

1. I find that NOS tubes can be bought for at least $75 a pop and
that's more than I want to spend.

2. Please let me know which among the current production tubes can be
recommended. Like everybody else I seek sound quality and reliability.

3. Can you recommend dependable dealers for this transaction?

Isaacson