It does blow my mind at times. But you have to remember a few things. If someone is selling KT88 for $20 each, that is below cost. Or in one case two dollars above. Who will work for that kind of money, including doing the buying, pack, ship, and test? And the cost of rejects?
Tesla is notorious for not taking back tubes that are defective. In fact, we negotiate knowing we won't get back a penny. If properly tested for all parameters, you will kick out maybe 20% if them.
All parameters means also tubes that draw excessive screen current. No commercially built machine tests for that. We had one built. And it costs thousands. In some amps, you won't have a problem. In some larger ones, you will break the amp.
So saving a few bucks may or may not be worth it. Ask SPECIFICALLY what is tested.
I have a lot of $$$ in defects here that I won't sell to end users. There are known parties that buy tubes that are out of spec. They test 'em on a TV-7 and sell them as "new, tested" which in fact they are. But doesn't mean I would use them! But these tubes do not disappear.
Tesla is notorious for not taking back tubes that are defective. In fact, we negotiate knowing we won't get back a penny. If properly tested for all parameters, you will kick out maybe 20% if them.
All parameters means also tubes that draw excessive screen current. No commercially built machine tests for that. We had one built. And it costs thousands. In some amps, you won't have a problem. In some larger ones, you will break the amp.
So saving a few bucks may or may not be worth it. Ask SPECIFICALLY what is tested.
I have a lot of $$$ in defects here that I won't sell to end users. There are known parties that buy tubes that are out of spec. They test 'em on a TV-7 and sell them as "new, tested" which in fact they are. But doesn't mean I would use them! But these tubes do not disappear.