I think that it might be a matter of taste. 

On my Quicksilver amps I can use both types. I prefer the sound of the KT88 compared to the EL34. It all depends on the speaker that you are using. I find that the KT88 sounds bigger and brighter than the EL34!

https://upgradehomedevices.com/kt88-vs-el34/#:~:text=Bass%20of%20KT88%20and%20EL34

IMO purely a matter of preference. I have sets of both, but generally lean towards the EL34 sound… finesse over power 😉…

There's a bunch of variables involved.  It's a matter of preference, the brand and age of the tubes, the unique circuit it's playing in, synergy with the system, and a whole bunch of other stuff.....definitely not an absolute.  It's also one of things i love about using tubes....try a new tube, and discover a bunch of new subtle tonal characteristics. 

That's probably why I kept my Quicksilver Mid Monos.    They ship with EL34 but can take any EL34 or 6L6 variant.    I've used KT 66,77,88 but I lean more toward the EL34 so I will put them in my system occasionally.

I have a 300b too and prefer that but sometimes I'll mix it up and put the QS in 

It is a matter of taste and specific implementation.  While there are some rough generalizations one can draw about the sound of particular tubes, I don’t see such generalization extending to the KT label.  I generally don’t like the KT88 tube, but I do like most amps employing the KT66 tube.  That tube sounds most like the 6L6, another tube I like a lot.  

That's another reason I like those QS.   Sometimes I'm looking for a different presentation and will re tube with a 6l6.    My last quad was 6l6,  was just missing the el34 tone a little

I think it’s hard to make an EL34 not sound sweet. You have to really mess it up. The larger KT tubes will (by comparison) give you brute force, dynamics, impact - but it’s hard to keep all that while getting them to sound as "sweet" at the same time, as the smaller tubes which seem to do it so naturally (EL34, EL84, 6L6’s etc). I think VAC’s recent high-end lines do a GREAT job at that (plus next-level articulation and refinement), but takes some doing and ain’t cheap.

Vintage tubes amps are a lot of fun and a nice break from the "hifi" sounding amps because they’re so inherently musical. Part of that, I think, is the use of those tube types. But there are those limitations - power, and usually bass impact / dynamics.

Matching and preference will play a role which one you like.

mulveling, "ain't cheap" is an understatement, VAC's top and near top of the line separates are extremely expensive, but you say they are worth it.

I have no complaints regarding the dynamics and bass of the VAC Avatar SE EL34 based integrated. I suppose, it also depends a lot on particular signal tubes that you use. These 60 watt/ch in ultralinear mode sound quite powerful.

So, there is something inherently very musical in EL34/EL84/6L6 tubes.

I love the sound of EL 34 tubes, reminds me most of tube amps from the past.  A ripe romantic type sound but without any bass slam. 

@yogiboy On my Quicksilver amps I can use both types. I prefer the sound of the KT88 compared to the EL34. It all depends on the speaker that you are using. I find that the KT88 sounds bigger and brighter than the EL34!

+1 yogiboy. 100%, so true. Was just sharing this on another thread about this, its a fact. Matching to your preferred sound is key, all speaker dependent for sure.  

Agree with most posters here, EL34 easily my favorite push pull amp tube. Sweet, natural mids, highs may or may not be rolled, depends on amp, bass is biggest issue. Bass issue is lack of slam, can be too resonant in some situations. Power supply in amp/speaker choice key here, get this combo right and bass can be ok. Still any KT will beat it on slam, extension, problem with KT is never get that same sweetness, natural mids, highs can be pretty nice, mids are the issue for me with KT.  I also generally agree the lower power KT sweeter than higher power.

In the end, the EL34 and push pull didn't do it for me, transitioned to 845SET than 300B SET. 300B is a magical tube with the right speakers and properly engineered power supply in amp, with this no roll off in highs, no soft, overly resonant bass, some totally misguided on stereotyping 300B sound. The boutique 300B tubes absolutely necessary. Running 300B in parallel can be replacement for those running EL34 with speakers SET can't handle, some very nice amps in this category out there.

If midrange is not right, the rest doesn't matter.

Power cord can make quite a difference for dynamics and bass, by the way. I use older Purist Audio Dominus Ferox, appears to be a perfect match.

Absolutely correct about 300B amps. So much is the power supply. In fact, it took an expensive, properly engineered 300B amp to open my ears to this tube as viable. Have never heard a good 300B amp for less than 15K. 

in my experience:

in General, Absolutely.

The VAC 80/80 was KT88s, good sounding $2,500 amp but it chewed up KT88s, and it bias drifted. I had an MV52, that was sweet, perhaps beige like the front panel, but lacked any real punch.

I also used a VAC Ren 30/30, gorgeous but it chewed up 300Bs and a Ren 70/70 - outstanding in every way but broke the bank chewing up 300Bs - 8 at a time!

I still have the 30/30 (no tubes), it has something awry as it makes very unpleasant noises, probably a cap is blown!  I met Kevin Hayes at Sound by Singer (early 2000s), he opined that the 30/30 might have been the best sounding amp he had ever designed, but it was not a commercial success, he could not sell it for a price that was profitable.

Some people will just listen to 300B based amps and nothing else, I heard.  They consider 300B to provide the purest midrange of them all.

RM-9 wrings quite a bit out of EL-34 but Roger was a genius… Like Gordon Gow and the 6L6 MC240… but really no meaningful conversation is possible without also considering the massively important imo ….output transformers…. 

IF a VPI magic brick on the output xformer significantly alters the sound for the better, you know they skimped….. 

Just a thoughtful guess but given the changes in sound when switching the same kind of output tube by different manufacturers, the make of tube may have as much influence on the sound as the tube type.

Design. 

Something from the guitar amp world. EL 34s have a different distortion signature to 6L6s - an evolved KT66. 34s clip more quickly but have a smoother distortion - think of a Marshall stack v a Fender Twin Reverb.

However, we use Marshalls because we want them to distort. Not something we look for in a hi fi amp.

300B / SET DHT bug hasn’t bitten me yet - it’s nice but I’ve heard no special magic I "gotta get". To be fair I like to listen louder than most audiophiles, and with more hard rock; the power limitation can cause some nastiness at higher SPLs.

I met Kevin Hayes at Sound by Singer (early 2000s), he opined that the 30/30 might have been the best sounding amp he had ever designed, but it was not a commercial success, he could not sell it for a price that was profitable.

I’ve heard exactly that about the VAC Renaissance / 300B lines, from multiple sources. They’re still sough after. The monos generate more power than most, and might be right up my alley, but I haven’t gone there yet.

But it’s also been a while since those days, and I can say that VAC’s KT88 based amps have come a long long LONG way since the past, even the 2000s (I used to have their little Auricle monos) - in both sound and price :(

RM-9 wrings quite a bit out of EL-34 but Roger was a genius… Like Gordon Gow and the 6L6 MC240… but really no meaningful conversation is possible without also considering the massively important imo ….output transformers….

@tomic601 I’ve always surmised that the MC240 would sound amazing to me. 40 watts is juuust close to enough for my needs :) I might have to try one some day. Yes, output transformers are crucial - avoid the bad ones - a lot of the good-rep vintage amps are renowned for their OPT’s (even Heathkit and Eico used Acrosound, Peerless). I imagine this is where the Chinese tube amps typically skimp. Some of the later Carver amps also got exposed for way undersized OPTs.

KT77 FTW

I use a Grant lumley desgn point to point wired ST70 reference Stereo Power Amp currently I'm using Gold Lion Quad KT88; 2x RCA JAN NOS ECC83 & 2x Gold Lion ECC82.

In this design ECC82 (12AU7) tubes are used as a preamplifier or driver tubs. They are a lower gain compared to the ECC83, making it suitable for applications where a moderate amplification factor is needed.
The 2x ECC83 (12AX7) tubes are used as a high-gain preamplifier tubes providing the a higher amplification factor, making it ideal for initial signal amplification

In the Lumley ST70, these tubes are used in the input and phase splitter stages to ensure proper signal amplification and phase splitting before driving the output tubes.

I can use this amp easily in ultra linear and Triode mode by simply switching them when placng the amp in stand by mode briefly.

Ultimately it depends on my mood and our source material as to my preference but very simply put the amp sounds more incisive and dynamic in ultra linear and just a bit sweeter and holographic in triode mode.

I have completely recapped the amp using Mundorf Mcap Supreme Silver Gold OIL 1200VDC film capacitors for coupling along with top end Nichicon and Audionote elsewhere. Topping off with massive Nichicon reservoirs/ Filter caps. The amp has huge hand wound inputvand output transformers and can now be set to output into 4 ohms or 8 ohms via Rhodium binding posts.

I will never sell it its such a thing of beauty and sounds as good as it looks. I think fir me as long as the KT88's are as good quality as I can afford the major sound changes come via sourcing top quality ECC82  & ECC83 and experimenting although I am so satisfied with how this ampmperforms hooked up to a Tim De Pavaracini designed all tube EAR 912 pre. I just dont feel the need to tinker, its powerful enough to drive my Proac Carbon Pro speakers down low with ease its very holographic and sounds dynamic even at late night listening levels.

I love my tube based system but I don't dicriminate on source I have a much modified LP12  decent digital source streamer about to be made even better by a Chord TT2 & M Scaler a vintage Sony CD player & Tube based CD player too. I'm  not too much of an Audiophile niw that I am listening to music much more than the system. It must beca sign that I'm close to where I want to be gear wise. I just cant see me being without valves in my system.

I would say PP amp do sound great. It really depending on the design to get the very best out from it. The most common problem of the manufacturers are trying to get maximum power from the amp; more the better. However, it pushes the power tubes working in the non-linear Class AB region. Even though the THD figure looks good, it doesn't sound right at all. 

My friend built a PP amp with 807 and I built one with KT66, EL34, or 6A3. The output power is less than 8 watts because we set the B+ to around 320Vdc and idle current of the power tube at 60mA. Also, both driver and power stages are using CCS at the common cathode to form the full differential/balance stages. 

We are so surprised how good our amps sounds that surpassed the single ended amps that we ever built.

Johnny

I noticed that both KT150 and KT170 are very linear in triode mode like the 300B and 845 DHT tubes. 

I expect they are the excellent performance if they can be used in small/medium power class A environment. 

it's purely a matter of design

@inna That's the answer.

If you want to hear a really musical KT88 based amp, the Harmon Kardon Citation 2 (properly refurbished) is a good place to start.

It makes a difference too if the amp is pentode or Ultra-Linear and also what class of operation its set up for. You can't get away from the simple fact that the larger the output transformer is, the more critical it becomes and the harder for it to make bandwidth. IMO this latter issue might be the most important.

Ralph, I see.

I have an EL34 headphone amp that sounds quite good.  Among pentode/tetrode tubes, my favorites are very low powered tubes.  I run 349 output tubes in pushpull that deliver about 4-5 glorious watts per channel.  This is my favorites tube aside from the truly crazy rare 252 tube.  My next favorite is the 350B (a variant of the 6L6 tube), followed by the 6L6 or KT66, and then EL84 (a tube often used in less expensive amps, but, I’ve never heard an EL84 amp I didn’t like).  
 

Of triode tubes, either pushpull or single ended, I particularly like the 45 and 2a3.  

Larry, what speakers do you run with that 349 tube based amp ?

I’ve been listening to the EL34 tube for over 35 yrs and have compared it to many power tubes. When it comes down to which tube is more musical, the EL34 tube is simply the better tube in my opinion. I own several very expensive tube amplifiers that operate strictly on the EL34 tube.  I really am not a fan of KT tubes except the KT66.  The KT66 I like very much and highly recommend it. I find the KT66 more musical than the EL34.  The EL34 tube is sweeter and gentler with the detail than many KT tubes.  Most KT tubes sound hifi- ish. I’ve found the EL34 to have better resolution also over the KT tubes.  Even though I personally do not like many KT tubes, I’ve heard them in circuits where they sounded fine. So the design is important and can make a KT sound good to my ears but still won’t have the same inner resolution that the EL34 tube has.  I purchased an excellent $5,000 300b amplifier 2 yrs ago from someone who preferred to use EL34’s on his JBL monitor speakers. 

Larryi, I’ve heard a lot of those very low watt tubes you’re referring to and came to conclude that they sounded good when matched with the correct speakers but when not matched correctly, they didn’t sound any better than other really good tubes.  I’ve heard 300b’s out perform the 45 and 2a3 in areas of liveliness and dynamics and openness. I understand maybe it was a power issue and probably needed more efficient speakers. 

interesting thread. I recently completed an Elekit 8200R, which comes with 6L6GC output tubes but can run with EL34, KT66 and 88. It’s a sweet sound with my 95db speakers. So of course I’m wondering what other tubes sound like. But I need to switch from ultralinear to triode and listen a while first.

Last year I purchased an Aric Audio "Push Pull" amplifier with upgraded caps, EL34 and 6SN7 tubes. This is my first Push Pull, and it is brilliant like all of Aric's gear. The amp will accept KT88s, KT120s, and KT150s as well; but have kept the EL34s in right now.....but I do have a pair of KT88s and KT120s around, I'll give them a try once I get my system back together

Inna,

My speakers are S.A.P. J2001 (twin 12” Alnico woofers, bullet tweeter and midrange horn sitting on top) but the midrange horn and compression driver replaced with a Western Electric 713b driver and KS 12025 horn.  The system is 99 db/w efficient.  

Larry, I see.

So, as important as it is, design is not everything. Tube types have intrinsic qualities.

The EL34 tube is sweeter and gentler with the detail than many KT tubes.  Most KT tubes sound hifi- ish. I’ve found the EL34 to have better resolution also over the KT tubes.

@lowtubes In this statement the thing you are not taking into account is the effect of the output transformer. For that reason you can't draw a conclusion since that is such an enormous variable! 

I don't doubt the EL34 can sound better because the output transformer typically doesn't have to handle as much power. For that same reason the EL84 sounds better than the EL34 (probably also because the EL84 is so much easier to drive...).

I suppose everything is important.  There are drop-in replacements for the 349 that sound very good, and I could easily live with the MUCH cheaper alternative.  However, the 349, as used in my amp, is run very gently and will last a very long time so I don't worry about using it up I have spares).  The input/driver tube for my amp is the 348 tube which is also a very expensive tube.  It too is better than its drop in replacements, but that drop in replacement is very close in sound and is extremely low in cost.  It is almost impossible to find 348s being sold.  The last pair of supposedly NOS tubes I saw sold for $2,000 each (I need four), and some crazy person was selling dead 348s to Western Electric collectors for $1,600 each.  The drop in replacement sells for around $8 a tube.  These days I run the $8 tube in my amp and in my linestage which also uses the 348.  My linestage also runs 310a and 310b tubes, and these are becoming pricey too.  

How much one is wiling to pay to run the very best tubes for a particular amp is a matter of personal priorities and finances.  I know people with magnificent clones or rebuilds of Western Electric 124 amps that run 6L6 tubes in the amp because the better sounding 350B tube is too expensive, in their judgment.  I can understand that choice as the 6L6 in these amps do sound pretty good.  

For my personal taste, I will take a 124 amp (pushpull, two output tubes per channel) running either 6L6 or 350B over all of the 300B SET and parallel SET amps I've heard.  My 349 amp is a clone of a Western Electric 133 amp and sounds very similar to a 124 amp.  It has the same output transformers as 124 amps, but it also has input transformers that the 124 does not have, and it outputs a little bit less power.

Then maybe I should upgrade output transformers in my VAC Avatar with custom ones ? This is a crazy idea, I think.

Then maybe I should upgrade output transformers in my VAC Avatar with custom ones ? This is a crazy idea, I think.

@inna Could be... The output transformer is the most critical part of any tube amplifier. Its only crazy if you think so... You could easily wind up (if you see what I did there) with a garage full of prototypes trying to get it right.

The higher the amplifier power the harder the transformer is to do. It is exactly this reason I designed OTLs instead and prefer smaller tube amps if transformer coupled.

Then maybe I should upgrade output transformers in my VAC Avatar with custom ones ? This is a crazy idea, I think.

Inna case this was serious - don’t do this. You’re not going to out-expertise nor out-voice Kevin Haye’s choices for his own amplifier. You can certainly out-budget him within the context of an Avatar SE, but at that point - just explore any of VAC’s newer, more advanced models released since the Avatar.

"Then I can’t use my Mullard EL34". Yep! Them’s the breaks. Kevin’s done wonderful things for KT88 tubes since then (pricey, though).

Final thoughts: don't do this.

mulvelimg, you are right of course. I have no intention. Upgrading to newer VAC integrated might be a possibility for a more distant future. But I like this one and would probably go with separates if decided to upgrade. I won't give up my Mullards easily, you are right about this too !

Different thing perhaps but I have a custom dual voltage transformer in my Nakamichi 682ZX deck. Willy Herman, a famous Nakamichi technician, had a few ones and installed it in my deck years ago. The deck does sound a little better with the custom one but the difference is small. Willy said that the quality of this transformer was much higher than original Nakamichi.