Siemens EL 34

@jjss49 In the 1980s there were International brand EL34s made by RFT same tube that RFT made for Telefunken, Siemens, and others. Not sure if there is a connection there or not.  I recall my buddy who passed had some Telefunkens in his RM-9 MK II. Was always kinda nervous about running them hot and having to keep spares around. Sounded really nice though, heard them with a variety of speakers back in the 90s. 

@jjss49 "...where i did most of my el34 based listening back in the late 80’s, with early big proacs, spendors, quads, maggie mg iii-a’s".

While I had to move on to different amps/ouput tubes for my main custom speakers 93db/6ohm, aside from triode amps which I no longer own, el34 is still one of my favs. Since my friend who owned the rm9mkii passed on, I don’t think I’ve heard a better musical el34 based amp since. It did get warm and he did go through tubes, usually working to keep a backup supply.

@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. I do keep my eyes out for something substantial for a 3rd amp in both stereo and mono amps for EL34s and not referring to smaller transformer amps. I do run QS Mono 120s (big quality transformers) now with KT120s and certain caps and cables I like to try and recapture some of that EL34 sound, yet its not the same type of sultry EL34 sound the rm9mkii and one of my former and larger Cary amps produced.

I might even try to source a custom scratch builder who can build to a higher spec, using the transformers and higher quality bits I want - for a robust EL34 keeper amp. We can take it offline on msg if needed. Thx.

@pdreher I have a pair of Quicksilver KT Mono's with KT-150's on order... so I'm hoping they will scratch my itch and quell any regrets I may have in selling the RM9 MK2.

Thanks for making the correlation and for sharing this update. For one, the KT Monos will run cooler. These Monos should sound quieter, with a darker background.  One thing to note fwiw, KT150s in my QS amps took 200-300hrs to settle in, relax, whatever..before the tone I was looking for started showing up. Some people say they are more linear.  I wanted something closer to EL34s, so I removed the KT150s and now running KT120s, a little more rolled off on top. Will be interested in your assessment after 200hrs on the KT150s in your QS amps.  

@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.

@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?

@pehare gotcha, and a forum member colleague here started that QS Facebook forum, I visit there sometimes.  I noticed your comments earlier about mid monos too.   With Will's amps, did you get the pentode push-pull or triode version?  He tends to use the factory Dynamo transformers in his builds and I've wondered if his amps have enough drive for lower sensitivity speakers in the mid to high eighyt sensitivity range. I've never tried one and we conversed some about different builds. Good fun, enjoy! 

@pehare well, not to rain on the parade, yet perhaps I can share this if it helps, and what I learned recently. You and I have both owned the SLI-80, and have heard what some may refer to as parallel single ended triode switch mode sound in that amp. You also know what UL switch mode sounds like in that amp... did you like the UL setting in that amp? IF so, what you have right now with Will’s amp is similar in UL mode, one might stretch to say - when using the same tubes and caps.

Here is the catch, for the QS Mid Monos, the "50% Triode" caption and unique description is something I asked Mike at QS about directly two weeks go. I don’t think it’s secret or proprietary info. I asked about the circuit function, and what it really means in his words. This was the reply - "It is 50% ultralinear which is half way between triode and pentode operation". A friend has a pair of the QS mid monos and I brought over my Dennis Had Inspire Hot Rod amp to compare. The Mid Monos were classic EL34 sound, a bit more forward stage, midrange was truly present, yet not nearly as recessed or set back type of sound stage as you might hear with one of the little single ended Inspire amps Dennis use to sell or the SLI-80 in triode switch mode. Depends on what type of PSE/Triode sound you might be looking for. As you know, Will also makes a type of parallel single-ended / triode wired version of his amps too, fwiw. I wonder if Will could reconfigure your current 70 amp and get it closer to what you want, instead. I don’t know if that would require a transformer change or anything. He’d be someone to ask. Would be interested in his response back to you.

@pehare have you tried GL KT77s in that amp by chance? 

I'm considering searching out a good very good designer/builder to commission and build a nice pair of monos for me in single-ended or parallel-single-ended (if I can find the right builder who is capable of the project with a proven circuit).  To start I would likely use really good EL34s or KT77s. More than a few friends have run the newer KT77s at my suggestion and all of them see quite pleased.  Maybe a little more power and retaining a bit of that 34 velvet.  Will be interested in your feedback on KT66s in Will's amp later on if you try it down the road. 👍