KT-150 Tubes- Push Farther or Replace?


Hello All-

Seeking advice from others that may have been in this spot before. I’m currently running my trusty Audio Research GS-150 power amp and I’ve just crossed 2200 hours on this set of tubes. I have a new octet of KT-150’s waiting in the wings.

Within the last 200-300 listening hours I noticed that the bias was requiring adjustment after every 3-4 listening sessions. This seems to be driven by two of the tubes continually falling low in bias adjustment.

As the tube bias is slaved in pairs would/could it be beneficial to isolate the two tubes that keep falling low onto the same pair of sockets with the hope that bias can be more evenly maintained or does it just sound like it’s time for these to GO?

The amplifiers manual states that replacement should be around 2K hrs but I’ve read posts here stating 3K might be achievable. The current situation is lower quality bass response and weaker soundstage. Any thoughts would be appreciated.

designsfx

OP

this Mercury looks like a variation of the Accurate 157. Perhaps Accurate made it for Mercury, who knows

Seller says it works and takes Paypal, so if it doesn’t work, you have Paypal protection.

 

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same thing, a Jackson, ask seller if your tubes are in the chart.

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I don't know about B&Ks, but he shows an old tube and the unit registering tube strength and shorts, also takes PayPal, but it probably doesn't 't qualify as he doesn't 't say 'works' just shows it does seem to.

 

Those old emission tube testers aren't going to tell you much about how your KT150 (or really any tube) are doing. A MaxiMatcher and MaxiPreamp can be pretty useful tools ($830 + $990), but if you only have a quad of KT150 and 6H30 to worry about (the latter typically being very reliable), it's more cost effective to just keep track of the hours (check bias periodically) and replace when prescribed. 

A small inexpensive tester is still good to have. Better than none. I think, if you have tubes, it is ridiculous not to have a simple inexpensive one. You leave yourself in the dark.

They test for shorts and tell you, bad, weak, strong, and you can check new matched sets you buy; old ones people give you; stuff you get at garage sales; your existing ones.

Problem shows up, tubes test good, you know to look and find other problems, a bad connection, bad ....

I check all of mine yearly before thanksgiving.

I have a big fancy heavy Hickock or Jackson downstairs. The little 157 and the big one always agreed about shorts and tube strength, so I use the smaller/portable one.

Way back when, when I inherited my Uncle’s Fisher President II: Master Control Panel; FM Tuner; AM Tuner; Viking Tape Deck; Garard Changer; Pair of Mono Amps, Preamps added to the Turntable for MM; Multipath added for Stereo FM: I used to stand in line at the electronic stores until my feet and back hurt, people lined up behind me. When I got my 157, I checked them all at the store, then compared the 157. It agreed with the store’s monster.

Just the basics is confirmation they are not shot, or, they are shot.

My Cayin has 6sl7s and 6sn7s. Same size/look. I switched an L for an N by error, fine for a while: lost a channel, nothing obvious, found the blown tube right away. Without a tester, I would not have found my mistake.

 

The only thing those emissions testers are good for is maybe telling you if a tube is shorted or dead, the rest of those readings on those types of testers are very suspect.