I would be curious to learn if you eventually spoke with ARC and how they advised you? Did you stick with the 150s or the 120s? Thanks
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
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! |
Interesting. I posed this idea of pairing a really good 6SN7 triode tube preamp with good Class D amplifiers over on the ASR forum. They just about took my head completely off over there with their regular "perfect measurement" and "distortion" debates, before "listening". I ran my tube preamp and SS amps before going back to all tube monos. I bet your setup sounds very nice. Good for you mapman :) |
I ended up selling the amp. Both the KT150s and 120s sounded good, just different. I preferred the KT120s, but realised I the heat put out by the amp in my small room was a bit too much, and I decided to go back to the simplicity of a solid state power amp. I bought a Pass XA25 and an EAR 868 preamp and I am now happy with this combination. |
- 22 posts total