Siemens EL 34

@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

@jjss49 "but it is not as warm and rich sounding"

Yup, exactly. That particular sound...I hear ya. Its something I’d like to rotate back in once in a while, maybe with some smaller monos that i dont turn up so much, just for low level listening.

Wow, does this mean I could just tag along with your reports and save a lot of money learning vicariously through you on these other tube amps i’ve not tried yet!!!, hahah, you’ve tried more than a few. Nice!

All joking aside can’t complain with my current setup, and there is value in the added transparency, depth, stage (my EL34s did not have). And, with my KT120s (a little more rolled off on top - which I like) than my robust and transparent KT150s. My current mono amps are bigger transformer/purpose built for the big tubes - runs 600v at the plate and I can’t run KT88, KT77, EL34s or it will burn them up. The new QS KT Mono adds this flexibility, but still knowing you have to run the higher plate voltages to get the most out of KT120, KT150, KT170s now. Tradeoffs I guess. Something to be said about lower power tube amps too :)

Looking ahead, a nice little second pair of custom parallel single ended PSE tube amps, with EL34s would be sweet. Not sure I’ll go with the QS Mid Monos, diggin deeper they are ultralinear, not what I think of as PSE triode imo. I’m starting to lose track of the better custom builders out there, those who have a real handle on this stuff and can discuss different circuits they build on. Hope to chat more via DM or something, if you know of someone. Thx.

@pehare Surprisingly to me, the difference appears in the upper mids and highs and not the bass for the KT170s.

pehare, if I may ask, and since you have one of Will’s amps, and your comments about wanting to try a pair of QS Mid Monos - can you share a little more. How is the listening coming along, and what about the upper mids and highs are your hearing and prefer more or less of at this juncture? Does the KT150 or KT170 have more pronounced midrange in your KT Monos so far?

decooney I don't own the KT88's I was forwarding some comments as per my 1st sentence...sorry for the confusion.

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:

Now back to my comments - I'm enjoying Will's amp - it's the first EL34 amp I've owned besides an original Rogue Cronus Magnum that was tried and sold pretty quickly.