Thanks, they seem reasonably priced so I may give them a try.
Audio Research VSi75 - End of Tube Life? KT120 vs KT150?
I have recently bought a second hand ARC VSi75 amp. It came with both the original KT120s, which have about 250 hours of use, and some after-market KT150s, which have about 1800 hours of use.
With the KT150s, the sound is quite hard, cold sounding, tonally a little bleached, but with great dynamics, extended bass and treble, and much more three dimensional. KT150s are claimed to have a tube life of about 3000 hours, so these should be not much past half their life. There is no distortion or noise.
The KT120s sound warm, tonally rich, colorful and much more musical. But they also don't have the dynamics or frequency extension. Nevertheless I much prefer this sound.
Does it sound like my KT150s are at the end of their life after 1800 hours? This cold, steely, colourless sound does not match what I read about these tubes, but it also doesn't sound like the symptoms of normal tube aging.
A quad of KT150s is reasonably expensive. Is what I am hearing just the normal difference between KT120s and KT150s? If so, it is probably not worth the cost of buying another set of KT150s to find out.
With the KT150s, the sound is quite hard, cold sounding, tonally a little bleached, but with great dynamics, extended bass and treble, and much more three dimensional. KT150s are claimed to have a tube life of about 3000 hours, so these should be not much past half their life. There is no distortion or noise.
The KT120s sound warm, tonally rich, colorful and much more musical. But they also don't have the dynamics or frequency extension. Nevertheless I much prefer this sound.
Does it sound like my KT150s are at the end of their life after 1800 hours? This cold, steely, colourless sound does not match what I read about these tubes, but it also doesn't sound like the symptoms of normal tube aging.
A quad of KT150s is reasonably expensive. Is what I am hearing just the normal difference between KT120s and KT150s? If so, it is probably not worth the cost of buying another set of KT150s to find out.
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- 22 posts total
These comments here and others help to confirm what I’m hearing too between these two power tubes. I’m re-testing KT120s again after running KT150s for the past year. "Neutral" is a good descriptive word for the KT150s in my amps too, I agree. I was yearning for a bit more of the notable midrange flavor from prior amps I had before with EL34s and KT88s. My current mono amps are designed to run only KT120s or KT150s with larger transformers and higher plate voltage. The mistake I made the first time was not giving KT120s enough burn-in time in brand new amps with all new caps not settled in yet. Retrying KT120s now with better caps and better input/signal tubes fully burned in. This time around the KT120s have some time on them. Now, the midrange is more present, nice tones, not characteristically "neutral" like my KT150s are. The KT120s are hedging closer back towards KT88 sound a little, sounding better the 2nd time around. I think I understand a little more why some people prefer them. I like both for different reasons. Nice to switch back and forth every once in a while.
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The differences you describe do not sound unheard of in general when switching tubes. I stopped pursuing tube amps when I realized I was rolling tubes to get more towards a sound more inherent to SS: clean,,crisp and dynamic, not soft and warm. I would consult with the vendor for input in your particular case. Audio Research is one line I find I could live with. I use a ARC tube pre-amp with Class D amps in my system. That combo adds just a subtle touch of warmth (compared to similar setup I have with no tubes) and with no softening or rounding of the sound. Perfect for me! |
- 22 posts total