Tung-Sol kt170 tube started glowing brighter

I installed 8 Tong-Sol kt170 tubes in my Sonic Frontier Power 2 amp. One tube started glowing a bright orange, yellow at the lower portion. I hear no sound interference. Should I replace it? If so, replace paired, right channel quad or all eight for matching purposes? I did swap the tube into different socket and it is the tube.



I have never used KT-170 tubes only the KT-120. Perhaps you can find a used KT-170 with low hours on it, I would definitely replace the one that you describe is glowing different than the others.

Somewhere down the line, if you keep that amp perhaps convert to KT-120's they put out less power but are cheaper and perhaps more reliable.


Have you biased your tubes? Is your amplifier capable of accommodating the KT170? @ozzy has a point and KT120s maybe better suited for your application. I have had no issues running any of the KT series valves, 88, 90, 120, 150 or 170 as my amplifiers are built to accommodate operation with any of these tubes. Have you tried swapping this tube in another hole to see if it lights up like it is in the current position. If so it may be a bad tube. If not check you may have other issues. 

Your amplifier is rated for use with either 6550C or KT88 output tubes. It is not designed to handle the current draw of the KT170 output tube. In addition, as previously mentioned, your amplifier requires re-biasing when changing output tubes. I would heartily recommend pulling the KT170 tubes before the amplifier goes up in smoke.

The designer said the KT170 tubes would work. They are a new tube to the market. These were brand new and played for 50 hours for this to happen. Of course I biased the tubes. I’m pulling the amp and placing my solid state Arye amp back in. I’m almost positive I’ll go back to KT150 tubes. I don’t hear the prat that I got when I had KT150 tubes installed. They needed replaced, hence here I am.