Try checking with fellow audiogoners pdreher and clio09. clio09 is now RAM Labs and a great guy very knowlegable.
I used two quads in my Music Reference RM9 MK2 for about two years. I’ve since sold the amp, but held onto a quad for possible use in future tube amps. I consider them to be on the warm side of neutral... not thin, nor extremely warm. Bass is tight, but not as prodigious as Gold Lion KT88’s. I like them a lot... and they are dependable. Good tubes for sure!
I'm not sure what you are goals are... but other considerations based upon my experience using Music Reference RM9 MK2 as the host amp:
My new amps (only 2 days old and still breaking in) are Quicksilver Mid Mono's. At the recommendation of QS owner, Mike Sanders, I bought them with NOS Tesla EL34's which are full bodied with surprisingly strong bass for an EL34 tube with a darker sound signature. Really still early to judge these tubes and the amps, as I only have about 15 hours on them and they are still breaking in.
Ultimately, system matching and synergy with your chosen amp will play a big role as to what you prefer.
Thanks for your insights. My amplifier can use 6L6 or EL34 tubes. I find myself going up and back as each brings different characteristics to the sound. Interestingly I am currently running 5881; which to my ear sound the best. But I have noticed the NOS EL 34 world is drying up and wanted to get one more quad for the future. The RAM EL34 NOS and Tesla both seem interesting. Do you know if anyone is still stocking the Tesla tubes?
Yes, I have a set of Amperex/Mullard EL34. They are very nice indeed.
If you are interested in finding some, you should contact Early at HiFiTown; he often has nearly NOS tubes including EL 34. He is an encyclopedia of vintage tube knowledge !
His email email@example.com.
Only thing to keep in mind; he sometimes takes a little while to fill the order.
So I have two quads of Mullards; one is amperex and the other true Mullards.
My only point of comparison was the Groove Tube EL 34 . the Mullards are much richer sounding. I remember when I first used the Amperex Mullards, my son commented that it sounded like the musicians were in the room with us.
My 6L6 quads are NOS GE and RCA. I actually like the GE better.
Both are better than the stock Sovtek the amp came with.
I like the 6L6 better than EL 34 in my amp ( Leben 600). The bass is much tighter with the 6L6 and the sound stage a bit larger.
I also have 5881 RCA/ Tungsol.
They are wonderful.
Lastly I am embarrassed to admit I have two sets of Russian NOS 6n3cE which are very musical in the Leben cs600.
Clearly this is an illness; the search for the "perfect" tube. I have more tube life than biological life left. I calculate that I should have over 40 years of tube-life ( assuming a conservative 5000 hours per quad ). That should last me into my early 100's. Hopefully my hearing will last that long as well.
Hope this helps
if you can, show pics of the telefunken el34’s you are talking about
i don’t believe telefunken actually made el34’s ... in the 80’s in eastern germany rft made slim bottle dimple top el34’s that were labelled many different brands (rft, national, siemens, also telefunken and so on)... very decent tubes but in my experience not in the same league as true uk mullard, dutch amperex, or even, the later japan-made seam topped ones on relocated mullard tooling
ram (roger mojeski’s operation, rip roger!) is/was a tube seller and rebrander, a good one at that, but as such they source different tubes from different origins, test and screen, then silkscreen their logo over that of the original manufacturers', so the fact that these have ram printed on them in ram boxes does not tell you what underlying tube you have
here are a few links with pics to show you the various tubes that have been sold as 'telefunkens' el34's in the past
ebay old stock siemens tube set -- note the thin glass bottles (relative to the bakelite bases), dimpled top, two horizontal vents in the vertical plate, 4 staples on each side -- this is the rft east german made tube i referred to in my prior post... here is another example of a pair of the same tube but labelled rft ... here are more of the same tube, this time marked telefunken
’telefunken’ el34 set on ebay -- here is another pair of tubes on ebay... by their brown color base, the same width glass bottle, very rounded dome on top with no dimple, double ring getter construction on top, single plate vent, five round staples each side, that is a tesla czech made tube from the 80’s-90’s... closer in quality to true blue brit mullards or dutch amperexes, very good tube
here is a third kind sometimes labelled telefunken, in this case, labelled siemens... this is a yugoslavian made old stock ’ei’ factory tube... note very different construction with the pointed tip at the top... ei made these and also fat bottle el34/6ca7’s back in the day before the plant was destroyed in the war, these are equivalent quality as the rft's in my use, leaner sound, less body
in addition to the above there were indeed some (not many) real deal uk/dutch made el34’s that were rebranded telefunken back in the day... the link below is an example of these... they will have mullard or amperex production codes and d- or 0 shaped double getters, brown or black bakelite bases, even width glass bottles, relatively squared off smooth domes.... here is real deal uk mullard sold as a telefunken
so op, you can check the above against what you have
@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.
i have very fond memories of roger’s rm9-ii, which i adored... it was one of the 2 amps (along with kevin hayes’ amazing pa-90c quad chassis mono amps) 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
what a lovely amp sonically, and made to last forever, (big time back breaker though... the backside with those massive transformers in a row still make my back hurt more than 30 years later 🤣😅)
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.
I recently sold my RM9 MK2, despite many telling me to never sell it. Next to a VAC 70/70 Signature (eight 300B's in push/pull), it was the best amp I've owned. Time will tell if I regret it. 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.
@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…
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.
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
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, 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.
@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!
Hi decooney I have his ultralinear version and have Tannoy Stirling GR's which are an easy load and are a great combo (rig posted here). 35wpc seems to be plenty. I still crave more of a triode sound like the Cary SLI-80 F-1 I had years ago and wondering if the mid-monos would provide that since they are 50% triode driven.
@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.
Thanks decooney for all the valuable info. Will and I did discuss his triode version but given my power requirements decided UL would be the better choice. It does get loud here sometimes:) That and I’d heard another ST-70 (Chris Keller’s version which he builds UL) in my system and liked the sound. At some point I'll try some KT66's for a different flavor but overall it's a great amp.
@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. 👍
decoony, no I have not tried them. I'll probably play it as is for 6 mos. or so before I try different outputs. Yes, I've ready somewhere that the Upscale Audio folks recommend KT77's as an upgrade in EL34 based amps.
There's a minty pair of AES/Cary six-packs for sale on Ebay and craigslist not too far from my area - have you by chance tried those? Too many output tubes for me but I've heard they're great sounding.
@decooney I tried Gold Lion KT77's back when I owned a Music Reference RM9 MK2. I preferred Gold Lion KT88's and Siemens EL34's in this amp, as the GL KT77's lacked emotion and just sounded too clean & lean in my experience. YMMV.
i’m curious, in your comment below, are you referring to modern day production russian made gold lion kt77’s -- or -- the true-blue old stock british gec/mo-valve/genalex gold lion kt77’s?
in my experience, i still find the real deal british kt77’s to be the absolute pinnacle of all el34 equivalents, a step above even british mullard or dutch amperex el34’s.... silky smooth yet extended highs, dense yet tactile and delicate midrange with a beautiful spotlighting effect, and terrific control and slam down low (which the mullards lack to a degree) ...