Favorite Output Tube

[shoe11]

In my quest for a tube amp, the three main output tubes I'm finding are the EL-34, EL-84 and the 6550. From the tons of reviews and info I've read on them, the EL-34 appears to be the most "romantic" if you will to the music, while the other two appear to provide more of a solid state style punch. It seems to me that the EL-34 is the tube that gets the most raves. I'm also finding that in most brands lineup, the EL-84 is used in the lower priced gear and most of the high end pieces get EL-34. Now while I know that the output tube is not the only determinant in final sound of an amplifier, I'm curious to know people's opinions as to which output tube sound they prefer.

~shoe

[Deang]

Character of the tube will largely be determined by the circuit. Whether the amp sounds somewhat lush and romantic versus a more incisive and dynamic sound will depend on several factors, especially whether it's tube rectified or not.

EL-84 and EL-34 are both good tubes. Personally, I favor the KT-88 over the EL-34.

I've never heard the 6550, but I know Kelly doesn't think to much of it.

I would concentrate on circuit types first -- triode, pentode, ultralinear, or SET -- get that narrowed down first. Figure out your power requiements based on sensitivity of the speakers, room size, and listening habits.

Whatcha been looking at ?

[Allan Songer]

In push-pull configuaration there is nothing like the mid-range magic of a really good 6L6 (KT-66, EL37, 350B, early 6L6G).

[mobile homeless]

Dean is right here about the circuit having a lot to do with the sound coming from the various output tubes. It's amazing how different the SAME tube can sound in various circuits, which is why ascertaining quality and characteristics can be a tricky task. Take the EL-34 and KT-88. Dean mentions that he prefers the KT-88 over the EL-34. So do I. That is, in the AES Superamp, an amp we both happened to have in our possession for a time. Both were wired in triode with the main differences coming with the system surrounding the amp (the amps were also different versions with Dean having the upgraded DJH model). In this circuit, I actually preferred the Chinese KT-88 over the Svetlana EL-34. I thought the KT-88 had a cleaner bottom end with a bit more clarity across the spectrum. The EL-34 did have a more lush and romantic presentation as it were, with more air and perhaps a more forgiving top end. IT was not soft, but in this circuit it didn't seem quite as focused either. Count one for the KT-88, a tube that I find is step up from the more coarse 6550.

Still, in other circuits, I have loved the EL-34 and in my total push-pull days, it was my favorite output for the great tube-like qualities. The EL-34 in the right circuit can sound about as un-solid state as you can get. It's a very BIG sounding tube.

Enter the little EL-84. I had loved this tube in guitar amps of old but had not messed with it too often in audio. In all honesty, even though I had heard a smattering of EL-84 amps, it was not until I owned an EICO HF-81 that I realized what an amazing tube this was. Over a short period of time, it turned into one of my favorite tubes ever. While it didn't quite have the diffused biiig sound of the EL-34, it has the potential to produce better bass definition and a more cohesive sound on the whole. This little tube CAN do some great things. I think it overtook the EL-34 in some ways, especially when sitting in the lowly EICO HF-81, still one of my favorite amplifiers, this including separates and other exotic fare. The EL-84 may be small, but it has some serious guts in the right circuit. Jean-François and I have been mulling this over for the last four months...but one way or another, a full, no holds barred EL-84 amp is coming down the pike. I have been planning one for awhile...too long.

Of course, as Allan noted above, there are lovers of the various 6L6 incarnations. Allan would agree that the damn things DO need some quality NOS versions to bring it to the next level. I have only heard the 6L6 in amps at other homes and in other rooms, never in my own home for an extended time. I need some more exposure here. In the past, the various 6L6 amps didnt have me running to buy one, but that could have been circuit and implementation. I look forard to hearing more.

Now enter the full triode tubes. This is where the sound changes dramatically, losing some things and gaining in others. If you have been reading in here at all you know my love for single-ended triode circuit with horns. A single full triode tube such as the 2A3 with NO feedback and very little to pass through can be THE most open, unfettered, clear, life-like reproduction heard. Whether it be the 45/10/2A3/300B/V52 etc, these triode tubes used in the appropriate circuit with the appropriate system via 100dB and up speakers can be something that is VERY different from any other amplification device you have heard. Watts is just a number once your speakers coming in with a benign impedance curve and 100dB and up sensitivity. The entire reason I am here was to find a speaker suitable to run these ultra low watt amplifiers. I never liked horns that much until I heard them with good tube amps. I was around them in rock bands for years, driven by high power pro amp solid state. Some here LOVE this sound. It pinned me to the wall with ears back like a crazed, rogue cat.

Jean-Francois and I have been discussion the implementation of a sophisticated, ultra-simple, high quality 2A3 PP amp, possibly done in monoblocks. This will come in around 15w of full triode power something the single-ended version cannot achieve. Seems a lot of people have been grumbling about wanting this and I at LEAST just want to hear it as I have never heard PP 2A3. The 45 is another option coming.

Regardless, as Dean did state, the circuit and implementation of the tube is the thing of paramount importance as you can find excellent and more middling amps using any of these favs. The power supply, output transformers, quality and type of circuit, and implementation of all above really contribute to the sound. Still, the tubes do have some defining characteristics when placed in their optimum operating points.

MY advice it to start listening...

kh

[Deang]

"...quality 2A3 PP amp...will come in around 15w of full triode power, something the single-ended version cannot achieve."

Wanna bet?

[sunnysal]

can you say "Apollo"?

lol

Hey kelly, I am laying down long green for a wimpy 2A3 SET and you are moving onto a PP? what´s the story man!?

tony

[mobile homeless]

Close reading skills have not been your forte this morn, Dean. Something the 2A3 in single-ended version cannot achieve. There are single-ended tubes that reach over 20-50 watts depending on how hard they are run and the circuit involved. I just dont happen to prefer them as they lose some of the magic of the low watt variety.

I have even told you about them. Why the strange responses today? First we have death as not natural then this. Have you been soldering again with closed windows?

kh

ps- Tony, I will NEVER go without at least one fully SET amplifier ever again. You will probably find it in my #1 system as well. I do like trying different things however, including satisfying the curiosity for the quality of a PP 2A3 triode. Rest easy...sort of.

[Mike82]

I pretty much echo Mobile's sentiments. I really like the EL84 and EL34 in p-p or SE wired. The 6L6 (5881, 7581A)and 6V6 are also pretty good.

I have mixed opinions about the 6550 genre (KT88 and KT90) despite having reviewed and used them for a few years. They tend to be used in the more powerful tube amps. Out of the three, I liked the KT90 the best as I thought it possessed the most linear sound. IMO, they are too "heavy-handed" for Klipsch or other hi-eff speakers if p-p, but if wired in triode mode, they may be fine.

Of course, if you don't need a lot of watts, the SET tubes are a great choice. While the 45, 2A3, and 300B get a lot of time on this forum, more Forum members need to hear the PX25. I used to carry Art Audio in my shop and found the PX25 to be an outstanding tube amp (5 watts). Even Joe Fratus will admit the PX25 , while the least powerful in the product line, is the best sounding. The PX25 is my fave SET next to the flea powered 45 tube.

While there aren't any budget PX25 amps on the market yet, the Audion PX25 approaches the Art Audio's performance at almost half the cost.

There's a lot of choices out there and with the efficiency of the Klipsch products almost any tube will work. In the end, you'll have to find the "flavor" of tube you like.

Good Luck

[shoe11]

Thanks everyone for your very detailed comments and opinions. I'm really looking forward to experiencing the various tube sounds everyone speaks so highly of with my 7's.

Dean and others~

I've been reviewing the product lines for dealers in my area so that I can start doing some in house listening. I've also been talking with Jeff (JCturboT) regarding the Stingray. Prior to his review I had contacted Manley and I have a dealer ready to hook me up with a Stingray to demo, but first I thought I'd try what I have available locally. I'm planning to go non-vintage. No disrespect to you vintage members. Just a personal decision.

Here's what I have locally and if there's a model I'm looking at. The majority of these I believe are ultra-linear though some can be made triode. Additionally, some are tube-rectified while others are SS. I need to do more reading on the issue of rectification.

Jolida - In particular the 302b EL-34, but any other model is available.

CJ - Looking at the CAV-50 EL-34, the rest of the line is available

VTL- IT-85 EL-34, perhaps paired with the ST-85

Cary

Antique Sound Labs

Atma-Sphere

SAP

Fi

Graff

Emotive Audio

Non-local, but planning for in home demo:

Manley - Stingray EL-84 or the Shrimp preamp with the new Mahi Mahi mono blocks.

Bryston - B-60 or the BP-20/3B SST PRO How'd that SS get in here?

I know most everyone in here is running Klipsch vintage with vintage tube. What I really need to know is who's running Klipsch Reference with new tubes. BTW the budget could go up to $4k at the extreme, but honestly I'm going to let me ears tell me what I like best and then my wallet will let me know if it's possible.

~shoe

[mobile homeless]

Actually, the majority here are running Klipsch vintage with modern tube amps (though many using variations of vintage circuits) but many have vintage as well. Most of the SET amps were made in the last five years with a few 300B earlier. Most of the guys running SET amps also have vintage. I could comment on a number of those amps in your list but I will let some others with more experience with the RF-7 do the duties.

kh

[leok]

There is an additional factor that has significant impact on sound quality from an output tube and circuit, and that is the "resistance" or AC loading seen by the output tube. In my KT66 pp amp I use either Valve Art or Sovtek output tubes. My power transformer is chosen and wired so that with 8 Ohms on the speaker terminals, the tubes see 16KOhms. Sovteks sound better at 8KOhms so I place an 8 Ohm 5W power resistor in parallel with the 8Ohm speakers. The Valve Art sounds like it's under water unless I remove the resistor, letting them see the full 16KOhms. I used to find the Sovteks shrill, but with the added loading they are my favorite. I'm listening to them now via the Fortes.

leok