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RE: Help with KT150 questions

I believe you have misunderstood what I wrote.

1) If a tester can't supply enough voltage, you test with voltage it can supply. After all the tubes will operate at different operating points in different amplifiers. If they test good at let's say 300V I don't see why they would not test good at 500V, for example. Obviously the values will differ and one should be able to say if the values measured correspond to the datasheet.

2) Self-bias probably means "auto-bias" i.e. cathode resistor. But it could be a CCS instead of the cathode resistor. This only tells us for sure that the user does not adjust bias for the tubes.
If your amp is self-biasing, the only thing that matters might be having matched pairs per channel. It doesn't matter if the tubes are matched strong, medium or weaker pairs - just that they are matched.
A matched new "weaker" pair is not a pair of bad tubes, just a pair of newtubes from the same batch that exhibit lower transconductance than the average tube in the batch. A "stronger" matched pair is similarly a pair of tubes that show higher transconductance than the average tube in the batch.
I said "get a quad of matched weaker tubes" because:
a) you declared preferring the original tube complement , which is not new, and has by now lost some transconductance, and I don't think the manufacturer would have requested the strongest measuring tubes for "factory set" - they would either request a medium set or even a weaker set. Tubes age differently and the stronger new tubes tend to loose more transconductance than weaker testing tubes from the same batch.
b) it was just an example of a possible choice and of course you can order any option from a serious reseller who knows more about tubes than that they are in demand and he should get in the business of selling because it will most likely bring in profit.

I hope it is clearer now what I meant.

On another note, I understood too late that I was browsing the "wrong forum". This one is probably for audiophiles who enjoy music and factory built equipment, but know little about how it is made or what is inside and how it all works. I guess that is the reason you got my post wrong.
******

http://rh-amps.blogspot.com/


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