Siemens EL 34

@decooney  another benefit to the QS is I'll only be swapping out four power tubes vs. eight power tubes in the RM9 MK2.

Good to know I should expect a 200-300 hour break-in before the KT150's are settled in.  

FYI, there is a Quicksilver Audio group on face book and an EE audiophile there who used to work for QS about 30 yrs ago remarked this about his new KT monos:

KT Monos w KT170s is what I’ve been running for the last 5 months and I’m loving the match. One thing I can say is that you must experiment w bias level. It seems that the KT150s are more forgiving on bias setting. Surprisingly to me, the difference appears in the upper mids and highs and not the bass for the KT170s.

With high gain selected KT170s they can be run in the 60W Monos and that’s not such a great match. More listening to do, as always…

I'm liking the Tung Sol EL34B's that came with my Will Vincent ST-70 although I have nothing to compare them to - it's my first EL34 amp and I think I'm hooked on the EL34 sound.  Now if I could just forget about trying QS Mid-monos and be happy:)

@pehare KT Monos w KT170s is what I’ve been running for the last 5 months and I’m loving the match. One thing I can say is that you must experiment w bias level. It seems that the KT150s are more forgiving on bias setting. Surprisingly to me, the difference appears in the upper mids and highs and not the bass for the KT170s.

Agree with this, having done quite a bit of experimenting with my QS M120s adjusting manual bias with meters listening to KT120s and KT150s biased at 40, 45, 50, 55, 60ma per output tube. The mids and highs tend to open up with added clarity and expanded sound stage as bias gets bumped up.

@decooney

@jjss49 would be interested in learning if you have ever come across another amp that comes close to or beats tine rm9mkii - in your opinion. I do prefer adjustable bias, and amps with top shelf transformers. I do see many of the smaller converted amps some custom builders do, kinda dinky w/baby transformers.

the short answer is no....

the longer answer ... is for el34 based amps, i have kept my vac pa90c’s all these years, they are a standard that remains unmatched, though i don’t listen to them often, they run the power tubes sooo hard...

from there i moved away from el34’s... first went with kevin hayes' ren30/30 then 70/70, after that i went all audio research for over a decade (kt88 based, then kt120’s), a big step up in power delivery, holography, if not tonality

in more recent times, i have tried the top primaluna amp (nice sounding but not very incisive) running el34’s.... then couple years back, on a lark, i tried a linear tube audio berning design zotl reference 40... it has a totally different sound than the vac or what i remember of the rm9... but it is absolutely spectacular in its extension, air and imaging, midrange nuance, but it is not as warm and rich sounding