KT150 to KT120..or KT120 to KT150

@daveyf, I had a Dennis Had Inspire KT150 Hot Rod amp for a year. Was nice, fairly resolving, yet I needed more than 10wpc for my larger 92.5 db amt/ribbon speakers.  And was sure the 150 tube could do more with more transformer and plate voltage behind it.  Sure enough, two years later ended up with the QS Mono 120 with KT150s. Wow, much fuller, bolder midrange, super transparent, hearing deep in to the sound stage, across the front.  Now he and crew are fascinated with KT170s. A good sign. Glad to see other new tubes coming out.  Would be nice to see WE do something less exotic and more mainstream.  Meanwhile I'm going backwards landing on a blend of old/new sound. Nice. 

My ARC VT100 MKiii  sound really good with 6550 compared ARC Ref 75SE KT150

VT100 MKiii more meat and more like the actual sound

REF 75se, more transparent sound and more like flying on the air ,it is beautiful, just different style

I personally prefer the sound of VT100 a little bit more.

I do not know if I install 6550 in Ref 75se,the sound could be better.

I am using the KT 120’s. I would like to try the KT150’s but I would need 12 of them and they are pricey. What if I don’t prefer them? Too bad there really is no way to just try them.

ozzy

The sound is definitely different with kt150 and 6550. Which one you prefer,I do not know. Each one has his personal preference.

I use two power amplifier exchangeable 2-3 days, and I feel good, and taste the difference.

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@ozzy for what its worth to you, while my purpose built mono block tube amps were designed specifically to run KT150s, nice, clear, pure, I am back to running KT120s again, now. Kinda missed the more textured (older) midrange, so I’ve alternated a few times. 150s are extra detailed on top, slightly larger and deeper sound stage if bias is turned up, but is the grass greener, maybe. The 150s can be so linear sometimes on my system, i miss that littlest of the midrange bulge reminiscent of EL34s, KT77s and maybe even KT88s. Popped the 120s back in, and there it is. Back and forth enough times now to know for sure in my setup.

Been playing again with bias on both 120s and 150s past six months. On my amps both tubes at 60ma are brighter. My ears are sensitive to bright sound. After 100-200hrs+ on both KT150s or KT120s, I decided on backing the bias down to 40-45ma per tube for low volume listening. Normally at 50ma. Just for grins, now sitting at 40ma with KT120s, lowest I’ll go. #1) saves the tubes a little longer, #2) takes a little of top edge off with bad recordings, and sounds nice. No fatigue at all. Save the $, keep enjoying those KT120s! I have zero desire to put the KT150s back in, and not for a good while. Like them enough that I had a spare quad set of KT120s stored too.