KT-150 Tubes- Push Farther or Replace?

"The current situation is lower quality bass response and weaker soundstage. Any thoughts would be appreciated."

that’s it, new tubes!

I’ll add my advice, get your own simple tube tester, to test existing tubes; new tubes you buy; and any time you need ’it’s not the tubes’ confidence answer when something else is ’off’.

OP

I use an Accurate Model 157, this is slightly larger 257.

Don't let the rust on the hinges scare you, they all corrode/rust. 

here's the one I use

You need to know it can test your tube types. I got a 257 for a friend, kept the 157 for myself, so we have both books.

If interested, give me a list of your tube types and I will check for you.

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.

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.

invalid.

I'm saying, let go of perfection, go for basic knowledge, I think most people will NOT spend for a big/better one.

IF it just finds shorts, not knowing and continuing using them can be quite harmful to your transformer, amp, 

If they appear to work, like an inexpensive sound meter: they do not need to be accurately calibrated. They will be relatively accurate regarding strength as well as find shorts.

If meter shows bad or weak, even if off a bit, relace them, and test the new ones. the results tell you about your tester, and if they are ’matched’ the meter, if not calibrated, will still show you if they are closely matched.

Better than being helpless, in the dark.

You advice is very good, IF people will spend the money for ’real’ testers. I read very little about member’s tube tester results here. My friends don’t have them, they rely on me.

Can you give a short list of testers, perhaps a few to look for, and pick a current eBay listing or two of better ones.

Some newer tube amps have visible and external bias adjusters, many do not, sadly my early Cayin A88T adjusters are internal. Again, I suspect only those with external adjusters use them.

I got the info to adjust mine internally, including advice here, then chickened out and took it to Steve at VAS. When I was younger, I’d have been in there with metal! Joking, I would have left it unplugged a few days, left it unplugged, deoxit, twist back and forth, and left them physically mid-point (i.e. no meter, just guess): ’good enough, close it up!

BIAS Meter.

OK, paraphrasing someone else:

a. setting bias is like setting the idle to a car's engine.

b. It's about when they are doing nothing, ready, but not about when they are busy amplifying, correct?

Bias effects tubes at their idle stage. You run them within a range, cool to hot, yielding more or less life. You can see/feel if they are running hot.

Bias can effect the output sound to a degree.

If amp allows use of different tube types, recommended to adjust bias  

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Questions (what does bias tell us about tube strength/matching strength?)

1. using bias meter, adjusting 'idle' of each tube, matching their bias:

does it indicate tube strength?

tube strength matching?

2. not holding bias is definitely a bad tube?

Can you find a 'strong, ok, weak, bad' tube strength via Bias?

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What I'm driving at is: my little tube tester has always told me about tube strength, and relative to each other strength, found any weak or bad tube, found any short, since my wife surprised me with it as a birthday present back in 1972, 50 years of answers that were better than flying blind.