EL34, 6550, KT88, KT120: Which Tube Sound Best? SOUND DEMO with QUALIO IQ Open Baffle speakers 

*Loudspeakers used in the video are Qualio Audio IQ speakers - www.qualioaudio.com?sca_ref=3235308.NKh93CeqLQ* Listen to how the vacuum tubes sound like. All tested with push pull Tsakiridis Aeolos Amplifier, Lampizator Amber DACSubscribe for more videos like this one And have a wonderful day

KT120. The most live, the most transparent, the most airy and the most natural sounding. It sounds as if the system doesn't exist and you hear the musicians live in your room!!!!! Incredible test, thanks.

EL34 for me, smooth and well balanced across the range.

I loved the KT-120 valves. What struck me over and over is the much deeper soundstage and openness of the sound, along with deeper bass and extended highs of course. I've been running EL-34s for the last 2 years, and I feel it is time for a change of pace. These 120s are expensive and scarce at this point in time though. This is due to a war related price inflation on all valves. Thank you for this comparo.

The EL34 plays more continuous the wave of notes. The others kind of punch at the sound with quicker rise to full leaving the natural flow out. Keep in mind that these tubes are typically biased differently and as such the amp may or not adjust to the different filament current needed and higher bias. More strain on the power supplies for tubes not EL34. Thanks much for the test.

Taking into account we are listening to YT sound, I would say that all them sound similar, but I think KT120 has an edge the rest don't have. Thanks for setting this audition in such perfect way!

El 34 is the best one in showing vivid, emotional sound

KT120 most cohesive, realistic sound stage and timber.

KT120. The bass is deeper and the overall openness of the highs is evident. The EL34 sounds like the playing is coming from a narrow tunnel.

The KT-120s. Definitely.

Can you please upload an uncompressed version of the videos? Thanks

Sounds like more music coming from the El34 sweeter and cleaner than the others

EL34 is more open and warm, 6550 next, KT88 and 120 sound a bit recess and thin, this may be very general impression of mine, I am sure many other variables can come into play, the microphone used, the selected tubes, and also the amp itself, if it is a synergy with the tube selected. Thanks for sharing.

KT88 is my choice. It is much sweeter than the rest but seems like less powerful

Very nice contest,thanks. I prefer EL 34,its more natural and has a beautiful flow. But more important than kind of tube is the construction of the whole amp.

el 34 more harmonics, kt 120 wider deeper stage with very good tone! Personally I think that speaker is very audiophile not super natural sounding, impressive but not my cup of tea. I have heard the wolf van Langa which is similar but with field coil, it was magical, with different electronics a little less blown away but still very natural sounding. Great video to attempt this!

Your system sounds great on all the tubes. During the first half I do not hear a difference between them. I see the sun set and the label change, otherwise I would not know. Then the Four Seasons track comes on and I clearly hear it. By the next track my preference is the KT120. All the KT tubes have a transparent mid / upper, but the 120 also has bass. BTW, thanks for the huge effort you have put into these comparison videos. Most enjoyable.

Der aeolos plus ist ja für die kt88/6550 ausgelegt. Killt man nicht zwangsläufig die Elektronik bei Verwendung der 120 Röhren????

Are all theses tubes from the same company and are they new or NOS? Because that can be a huge difference in performance. But just by the sound of this video I prefer El34 than Kt88 than 6550 with your set up. Kt120 is over kill with your amp and that particular speaker

The EL 34 has the classic smooth warm sound. The KT 120 sounds closer to solid state.

Technically speaking these are not 'open baffle' speakers - but its not a complaint and I love your test and I am tempted

I am glad I have the KT120's in my Conrad Johnson Power Amps... Also in this vid its shown imo (on my old phone 😉)

El made for all round quality sound KT 88 grandfather BUT where it KT66 the grandmother (who gives us love) my favourite just soooo musical thanks for the opportunity to comment. 18:25

This is a very unique design. On next video can you please post in room frequency response chart like they do in Stereophile? Thanks!

Luv the Christmas tree.

EL34's sound is more open. KT120 is fuller than others. 6550 sounds hollow.

This sounds like the right sequence of elevation but I miss real SE amps

There is no one better here. They all had their merits. I would be which is stressing the amp. Which will have the longest life in that amp design.

6550 gives too much audible distortions. 88 gives less, but I don't like its high end. EL34 is more or less, especially at a mid range, but 120 is the top. It would be interesting to listen to a multi-amp setup with 120 at a low end, EL34 at a mid range, and .. something like 6SN7 at a high end.

To me KT88 and after KT120. It has the most natural, airy sound (with good separation & clean bass)! 6550 too dark with less separation.

Hi Sir, what a great demo and it's really wow me 😊 May I check what's the track u used for testing? Thanks!

Les KT 120 me paraissent beaucoup plus naturelles. Je ne suis pas impartial, je viens juste de recevoir mes blocs mono (Tsakiridis Apollon Ultra) chacun monté en double push-pull de KT 120.. Absolument phénoménal de transparence, de qualité de timbre, de dynamique et de profondeur de scène sonore..

I'll stick with my EVS1200 (based on dual ICE Edge AS 1200 modules) and my LSA Voyager GaN 350, both of which can be left on 24/7

Kt88 BEST SOUNDING

All nce, but for me its the : KT88 very nice detail and more neutral and natural and still that tuby stage

Mega video. Many thanks. What recording software do you use?

El34s always. NOS Mullard xf2s and Tesla brown bases. And 6CA7s. Don't ever count them out. Especially the new EH 6CA7s. They're amazing

6550 have a beautyfull midrange and smoothy hights

Hi. I am hearing unexpected results, using older iPhone with Apple ear buds. The KT88 sound terrible! The sound is unnatural. My favorite are the KT120. The sound is natural and seems to isolate the instruments from one another, and adds depth. The EL34 seem warm, but almost muffled slightly or overly colored. The 6550 is pretty nice sounding. So I’m ranking them best to worst: 1) KT120, 2)6550, 3) EL34, 4) KT88. I believe this must be due to the iPhones limitations. I was expecting the EL34 to be good. It wasn’t. And why is the KT88 so awful?! Tell me why?

EL34 for me

Amplifiers that are advertised as swap-tube amps are and will always be a poor choice for the customer. The fact that there is some overlap in quiescent conditions that allows to use them all with minimal bias adjustment (or none at all) is a good marketing argument for the seller but it's a poor return for the customer who will have to spend extra money to find which of the tubes is actually fitting better (less compromised!!) in that design. Even worse if we are talking about expensive gear! I do not like any of the combinations, especially the EL34 can do WAY better than that and also produce some serious class AB power (up to 75W in pentode mode) without stressing the tubes at the same time. But it needs an optimal circuit, an optimal transformer and the use of local feedback ONLY. I have just made one....yes I am a DIYer and can design my transformers but anyone could get one, maybe with less power but overall great sound if swap-tube-amps (and in general swap-components amps) get binned forever.. Cheers

As much as I tried to prefer EL34, the bass on KT120 was just too good to ignore, I prefer KT120 for its sheer power

KT120 и 6550 наиболее объмный и басистый звук

KT 88 for the win

everything sounds great. playlist please

This cant really be done properly via RU-vid.. The compression and artifacts are too high. You start hearing (or wishing) things that arent there. Perhaps closer miked in a less vibrant room. I can however hear differences in speakers very clearly if recordings are done well. Thanks for the effort anyway

EL34 is most boring to me: lack of low end, lack of air and flat soundstage. 6550 almost same. Both KT better dynamics, low end, have air and more emotional. 120 may be more clear and "shiny" on top than 88. Thanks for your videos, helps to investigate without bying all of this staff)) I make myself some not expensive SET amps using old USSR lamps, was thinking about EL34, not anymore))

EL34 and 6550 where the clear winners. Far more open sounding.

kt120 for me

what brand tubes you use on the el34 bro?

I’m interested in the artists and song tracks!

voice better : 6550 < el34 < kt88 < kt120 If i liesten to music at there place then i choose different.

Do a review and include 300b & KT150

Geez, the KT88 is so much better than the rest it's not even close...all the rest sound like different versions of a "recording"...with the 88 it's so real and 3-dimensional that it's spooky

Nice comparison.

EL34

You have to compare different tubes on each song not one song at different tube s

what tubes you use on el34 bro?

EL34 is the more musical. The best with the first recording. KT120, clean sound. The best with classical. EL34 :( 6550, I can live with them. KT88 are the worst. If you listen to all kind of recordings: KT120 or 6550.

EL34 больше для красивых и весёлых жанров, а KT88 для грустно печального рока. Разве нет?

Is that glass or plexiglass on the open-baffle..? ✌

KT120 for me :) EL and 6550 very distorted, especially 6550

In this particular set up .............the 6550.............and the EL34 In fact comparisOns depends on many variables...........In reality one can only optimize an amplifier for a given tube type .........more , one can in fact optimize to one tube type or combination of tubes from a given BRAND FOR EACH TYPE USED... Same goes for the choice between triode mode and UL or pe,thode mode... All the options are marketing tools ............to fool audiophiles ... and no current production tube can compete or come up to the standard of GOOD nos tubes... Also tube amplifier technology is not made to drive MODERN current hungry and low impedance LS that need to be driven by high damping factors of heavily NFB amplifiers... This is a common made upmarketing error made to sell tube amplifiers to interested and curious audiophiles . But the marketing works and the sales follow............most modern tube amplifiers are not designed and build by the lost skilled engineers that had those skills.and the know how is lost . Clones of exceptionel old tube electroics like the famous marantz 7 or 9........are an illusion and don't even sound close tothe original. Exceptions exist but at a price ...........out of range of many music lovers. In this demo I repeat ....the 6550 ( whatever the brand ) wins ....and the EL34 on voices.... ..

KT88 this best for me

Is the woofer also open baffle, or?

thank u

KT 88 ... ! best voice

KT 88 BEST. 6550 WORST. But the McIntosh tube/soiid state hybrid amplifiers use the 6550 and they sound great; so other factors contribute to the sound.

KT120 is the best for me ..

Kt120 bigger soundstage, more space for instruments and more natural voice

I don't hear the differences in the last 3, the 34 has the highest mids, i think youtube, i have to hear in direct.

Я НЕ УСЛЫШАЛ НИКАКОЙ разницы!

EL34 FOR ME.

I think best sounds is if 6550.

For me EL34 or 6550

1st - EL34, 2nd KT120...

I closed my eyes... they all sound very close...

All are nice But➡️KT88...has the best midrange👍🏼... kt120 to much detail in your face, like the speaker box needs more foam🤣...el34 to soft lacks detail...

845 please :-)

10:00 song title ?

I couldn't tell the difference between any of the tubes. Then I realized you were streaming. A turntable with a high quality cartridge and phonostage would have revealed the nuances between the various tubes. Streaming is flat. Two dimensional. Lacks definition. The aural equivalent of a cartoon.

EL34 more space than the rest 😉

KT120 🎉🎉🎉🎉in

Kt120 sounds wide ambiance and richer

KT120 less tube (more impact) or EL34 even if it lacks bass control. On Vivaldi KT88 is a killer. 6550 on voices sounds horny or emphasis on these frequencies.

KT120

kt 88 takes it

I very much disagree with the test method and the conclusion. It is basic knowledge that the operating points have to be adjusted for each tube - then they all would sound neutral. All this proved is that the wrong amplifier was used for the comparison AND the wrong engineer made sure that the comparison was fair. If the output tube changes the frequency response (which changes the sound), then the amplifier has not been correctly designed.

EL34 sounds compressed, tube sound 😅 6650 no bass. KT88 no mids 😅 KT120 has the best sound and transients.

KT 120

6550

Any HIFI comparison on youtube is total bullshit. Firstly, the audio quality of youtube is bad and it is not possible to hear the difference, secondly, most people listen to this on a mobile phone or $20 headphones, so all you "experts" who claim to hear a difference are actually talking nonsense. I have an amplifier that also uses the mentioned tubes, modified CAYIN A55T and it is very subjective which one is the best. For vocal jazz and midrange i prefered hot biased EL34 for something louder, rock, pop, metal or electronic music where you need good bass and low range KT or 6550 is better.

Fix your room

i wonder what the responses would be if you would compare XF2 el34's to all the other tubes....🥲 the KT120 are defenitly Tung Sol as they are the only brand producing them, but which brand, edition are the others..? i think i see Prima Luna KT88's which are (pardon me french) crap tubes, comparing KT88 to KT120 you should at least put them up against the Gold Lions as they are in the same price range as the KT120, The JJ el34's are dirt cheap tubes, however the EL34L sounds much better then it costs. About the 6550, comparing Tung Sol KT120 with Tung Sol 6550 seems more fair, those look te be (but are not) the Sovtek 6550WE...?Oh i see now they are JJ's as well. the absolute cheapest 6550 out there.... No wonder almost all prefer the expensive KT120's, those tubes cost almost the same as the other 3 quads combined... Nice video BTW