Which Power Tube ?

Discussion in 'Audio Hardware' started by iDigital, Apr 16, 2019.

  1. progrocker

    progrocker Forum Resident

    Actually, the KT77 is an ideal drop in replacement for the EL34.
    SandAndGlass likes this.
  2. Subagent

    Subagent All I know is What I Read in the Liner Notes

    Arlington, VA
    Oh for heaven's sake, man. Don't leave it sitting there like that. Tell us why this is so.
  3. progrocker

    progrocker Forum Resident

    Because it's always been listed as such. I've been using KT77's in my fixed bias EL34 amp from the beginning(5 years) with wonderful performance and no issues.
    SandAndGlass likes this.
  4. Marshall_SLX

    Marshall_SLX Rega P9 #1 Fan

    Fair call mate but my consonance cyber 800 fixed bias amps dont accept them... they do accept el34 and 6ca7 however
  5. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I bought a little 3.9-Watt Decware Mini Torii amp a few years back. It is a single ended pentode design, running 6V6GT's as power tubes. It was fun to play with but not much power.

    After buying a 845 based Line Magnetic 518iA SET integrated, I was very impressed with what switching from class A/B to SET did for my system.

    One day, I decided to pull the Mini Torii off of the shelf and give it another go. One of the power tubes was out, I think it may have been a JJ, but I don't exactly recall.

    Digging through a box of tubes, I found a pair of Tung Sol 6V6GT tubes. I removed the JJ's and replaced them with the Tung Sol's. The amp wasn't sounding very good. As I had recalled, it used to sound better. I was doing something else at the time, so I had just left the amp playing.

    About an hour or so later, I caught myself stopping what I was doing and listening to the music that was playing. I was stunned! I couldn't believe how good it was sounding. Then I remembered. I has forgotten that I had just changed out the power tubes, it had completely slipped my mind.

    After the amp had a chance to warm up a bit ald the new Tung Sol's had a chance to break in, this little amp sounded wonderful. Though not as powerful, even better than the $4,500 LM 58iA, with it's 845 power tubes.

    This little amp with its modern 6V6GT power tubes, has turned out to be the best sounding tube amp out of the dozen tube amps I owned, both modern and vintage.

    I checked online, and the Tung Sol 6V6GT tubes I was using, run about $45 a pair.

    Go Figure?

    Darkened room to show the tubes. The large tubes in the rear center are the rectifier's.


    This is it sitting on top of the Line Magnetic.


    The amp is a dual mono design, with tube rectification and tube voltage regulation.


    It is a tiny little amp. The white top deck is only about the size of an 8 1/2" x 11" piece of copy paper. The amp underneath it, weighs 77-lbs.

    Otlset and HiFi Guy like this.
  6. Larry I

    Larry I Forum Resident

    Washington, D.C.
    Great pictures. Aren't the big glowing tubes regulator tubes, and not rectifiers? I have a linestage that utilizes six regulator tubes, four that glow orange like these and two that glow blue. This looks good, anyway, regardless of what they do for sound quality. Another sort of weird things about these tubes is that if they are not glowing at full brightness, you can prod them to glowing brightly by shining a bright light on the tube.
    SandAndGlass likes this.
  7. SandAndGlass

    SandAndGlass Twilight Forum Resident

    You are right, by bad! Those are two of the voltage regulator tubes.


    Tube Descriptions:

  8. Otlset

    Otlset the tree demon awaits

    Temecula, CA
    This is a neat and intriguing 'little' amp. My Avantgarde Duos will run *adequately* with a one watt/channel amp, although lacking a bit in dynamics. But this amp with 3.9 watts should really get them up and going. Bet the sound would be sweet.
    SandAndGlass likes this.
  9. SandAndGlass

    SandAndGlass Twilight Forum Resident

    It will!

    It is a very dynamic sounding amplifier.

    Here is a link to the MINI TORII SE DESIGN NOTES, I think you will find it interesting!
    Otlset likes this.
  10. Otlset

    Otlset the tree demon awaits

    Temecula, CA
    Very interesting read, thanks! It seems the tube rectification adds a lot to this amp, especially in how those tubes affect the sound signature of the output tubes. This amp sounds like a tube roller's dream amp (from the article)...

    "Using different output tubes in the Mini Torii SE was exciting because the variety of tubes you can use is so large and the differences in sound were so distinct it was possible to make the amp sound pretty much any way you like. Some combinations were harder sounding which served less efficient speakers well. Some were softer, even pastel sounding with completely different sound stages so it doesn't take long before a tremendous feeling of empowerment comes over you. It really brought the theme of this transparent and flexible little amplifier to be about the tubes themselves. If you thought the amp had a particular signature it was only until you rolled some different tubes in it. One night we stuck a pair of original G.E. 6L6 coke bottle shaped tubes in it from circa 1950's and they sounded just like a classic 300B amp!"

    What fun!
    SandAndGlass likes this.
  11. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I remember it sounding OK with the original tubes but I was not particularly moved by it originally. It had sat on the shelf for a couple of years till I brought it back out to play with it.

    It was only by chance that I put the TS tubes init, because I happened to have a pair laying around.

    This amp is only $2,200 for Decware. Mine has a 1/4" headphone jack and the stepped potentiometers as factory upgrades. I happened across it used on eBay and bought it for about $1,150.

    So here I have a $1,150 single ended amp that sounds fantastic with $45 tubes.

    I was excited reading the same thing that you posted about the NOS tubes.

    Something else that had caught my attention after I changed out the tubes, was the dynamics of the amp.

    "The Mini Torii SE was appropriately named because it has the signature, weight, and hit of it's much larger sibling, the Torii Mk II. Yet the Mini Torii SE is single ended giving it superior low level performance and detail - meaning it will sound more involving at lower volumes. On my corner horns the bass from the Torii MK II is impressive and impossible to ignore, yet on the same speakers the bass from the Mini Torii SE is actually better, tighter, flatter, and equal in amount."

    "The result still has me shaking my head. The Corner horns sound better with this amp than any other Decware amp to date, including the Torii Mk II."

    "During the day at work we find ourselves listening to the radio and Internet radio such as Pandora etc., and while it sometimes sounds almost hi-fi, most of the time it makes a guy like me suffer. Putting a treble dampening circuit in the amp that is fully adjustable, not in the direct signal path and fully defeatable makes it possible to listen to sub-par sources or recordings with far less distraction. At the same time many high efficiency speakers are fairly tipped up in response, having significantly more treble than bass. If it weren't for this trait everyone would probably love single driver full range speakers but the majority develop a love/hate relationship with them. This amp allows you to damp the top end as much as needed, and on the fly. So it has a dual purpose and I think many people will find it more than valuable."

    Everything they were saying, rereading the design notes page, correlated exactly with what I was experiencing.

    I have never owned a pair of 300B amps to run with the A7's, but one of the comments you hear about them quite often, is their smooth sound, but lack of dynamic's. I think that with either your speaker's or my speaker's, there would be no lack of dynamics. But, to hear dynamics with the 3.9-Watt amp is impressive and unexpected.

    With the 22-Watts the LM 518iA SET produces, it will power the A7's to rock concert levels with beautiful clean sound. That is more power than I would ever need.

    With the Mini Torii and the Altec's, the sound is so rich and full at lower volumes, I find that I don't turn the system up loud anymore.

    The A7's are 103-dB. in sensitivity, where you still have a few more dB's on me. Mine are a bit less sensitive because I have the HF horn padded down to match the output of the 828 bass cabinet, so the sound is linear for home stereo use.

    Keep your eyes open!
    Last edited: May 14, 2019
  12. iDigital

    iDigital Forum Resident Thread Starter

    Hi, Yes, I already was aware of the decware Mini Torii, your and subsequent posts are apt, as I am currently leaning towards a 6V6gt se build myself
    SandAndGlass likes this.
  13. musicera1969

    musicera1969 Member

    NOS EL34/6CA7/KT77 - affordable? Where?
    Hmmm - wait ........... I need 2 matched Quads or an matched octet for an tube Integrated. Do you think the tubes will cost very much?
    Been trying to find good 6CG7 matched pairs also. The RCA clear top - the pins are on the thin side.
  14. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Your best best, pricewise are NOS RFT EL34's from eBay seller's in Germany. They should run about $280/Quad.

    These are the realm deal that modern day EK34's or modern day KT77's can not match.

    I had modern production KT77's in a Line Magnetic 211iA integrated and NOS RFT EL34's in a L4, AN Kit amp.

    The L4 with the NOS RFT's is the Best sounding class A/B amp that I have, out of ten tube amps. It really is the first time that I have experienced the midrange magic that I have always read about the EL34's having, because modern day EL34's certainly do not.

    My preferences lie with KT88's for modern day tubes, but I think that the modern production KT77's sound nice too. Still I find that my preferences are the KT88's for modern tubes. They have a nice midrange, no harsh top end and plenty of strong, deep bass.

    While you will pay a bit more for the NOS RFT's, keep in mind that they are likely to last twice as long (or longer) than modern production EL34's, which are nothing to write home about anyway.

    This brings the NOS RFT's, not much more costly overall than modern day production EL34's and they sound so much nicer. They surprised me with the amount of bass that they produce, clean and natural sounding.

    When you talk about the large power tubes, there are very few affordable choices going NOS.
  15. iDigital

    iDigital Forum Resident Thread Starter

    If all of this talk about new stock tubes being inferior to new old stock tubes, I will also include old/used tubes, is there then any sound reason to continue with tube amps at all ? especially when new old stock becomes extinct and/or cost prohibitive ?
  16. pterodactyl

    pterodactyl Forum Resident

    Boulder, CO
    I like 6L6 type tubes, especially the Philips 7581A. My favorite tube for hifi and Fender amps.
    Joe Spivey likes this.
  17. TarnishedEars

    TarnishedEars Forum Resident

    Seattle, WA
    Some people can really be snobby about using NOS tubes. The fact is that some of the new stock tubes sound fantastic. The issue primarily is that older tube gear was voiced to sound best with the tubes which were available at the time. But new tube gear tends to be voiced so that it sounds good with modern tubes.

    I remember back in the 80s when I was buying cheap new-stock Phillips 12AX7s and 6L6GCs, and people told me how much better the expensive NOS Tele's and Mullards were. Now these same tubes which many people considered to be crappy back then are considered to sound wonderful by many people today and command huge premiums as NOS. So often times it all comes down to personal taste, as well as perceptions of value. These tubes were cheap back then, and so many people considered them to be crap compared to the older stuff at the time (and admittedly the quality control had dropped significantly by then). But now that these exact same tubes cost an arm and a leg, people think that they sound wonderful. Go figure...

    I have found from my own experimentations of tube rolling that often times I can get amps to sound amazing by rolling in strategic combinations of new tubes to achieve exactly the sonic flavor that I am looking for. Sometimes there are certain positions inside of an amp where I can't find a modern tube which fully lives up to my expectations. These are the only positions where I find that I am happiest running NOS tubes. Otherwise my system sounds amazing while running modern tubes in about 80% of my tube positions.

    But I could still run a combination of 100% modern tubes and be happy with the sound; just not quite as happy as I am while using a couple of NOS tubes in the chain.
    Last edited: May 16, 2019
  18. Salectric

    Salectric Forum Resident

    I agree completely! Back in 2002 I bought a quad of SED Winged C 6L6GC because Triode Electronics recommended them as a decent sounding modern tube. As I recall I paid something like $30-40 for the quad. Ever since then I considered them as disposable "el cheapo" tubes that I would throw into a new circuit just to make sure it worked. I didn't use them very often since my amps were really intended to use KT-77s or Kt-120s. But now I find out these SEDs are considered prime vintage tubes and can sell for as much as $450 for a quad. I now treat them with a lot more respect!
    SandAndGlass and TarnishedEars like this.
  19. iDigital

    iDigital Forum Resident Thread Starter

    I am not biased towards nos or new tubes, it comes down to availability, affordability and most important, how they sound, I was just getting the impression that there are no longer any new true el34’s being made today and that, in general, new tube manufacture is not up to the exact standards of yesteryear.
  20. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I think that TarnishedEars put it so eloquently...

    Modern day amps mostly sound different than most old amps do. They tend to be more powerful, more linear and have more sparkle on top and stronger, tighter bass on the bottom.

    I had twelve tube amps, some modern and some vintage. My modern amps sound good with their modern tubes. In general, for a class A/B amp, I have preferences for KT88 tubes and modern day KT88's match well and preform well with the modern amps.

    Buying NOS KT88's are so cost prohibitive, that one can not even consider doing so.

    In addition, we have tubes that are only in modern production, KT90's, KT-120's and KT-150's. These fit their modern production amps like a glove.

    But tubes are not the only nor are they necessarily the best answer to quality audio.

    As fond as I am with tube amplification, I only use it for my vintage Altec's and the Zu Omen Definition's (PrimaLuna KT88 based Prologue Five).

    Like modern amps are voice for modern tubes, Most modern design speaker's are voiced with modern SS amps and sound best with modern SS amps.

    Other than the Zu's, I run all of my modern day tower's and bookshelf speaker's with only SS amps and usually powerful SS amps.

    While I could use tube amps to drive them, I don't really see any point in doing so.

    Depending on your speaker's there may not be a reason to use tubes at all.

    With my vintage, horn loaded Altec's, tube do magical things that I have never heard a SS amp come close to.

    If I were to pick only one consumer product of the twentieth century to illustrate how manufacturing will never be there again, it would be tubes.

    If you watch this YouTube video of a Mullard tube factory, you will clearly see why we will never have the same tubes again.

    The process was so huge and involved, that it took factories on this scale, together will highly skilled labor to produce these tubes.

    But, before SS, every amplification device in the world used them. Today that figure would be only a tiny fraction of one percent, at best. So, as far as tubes go, we can not even hope of seeing those tubes ever again.

    That does not mean that we will not have tubes and maybe good tubes, just not those tubes.

    They have good modern EL34 tubes, but unfortunately they are just never going to be what the NOS tubes are.

    They will continue to manufacture and improve modern tubes. But, some of the best sounding tube amps are lower powered tube amps and for those, you will need speaker's with high sensitivity.
  21. iDigital

    iDigital Forum Resident Thread Starter

    Hi, Yes, I am gravitating towards a low powered se amp, vintage tubes and transformers, it will be my first one, so I am excited to experience it, still deciding whether to build it with 6v6gt, 6l6 or el34
  22. HiFi Guy

    HiFi Guy Forum Resident

    Orlando, FL
    If you build 6L6, you can also substitute 7581A.
    pterodactyl likes this.
  23. SandAndGlass

    SandAndGlass Twilight Forum Resident

    What kind of speaker's do you intend to power with it?
  24. iDigital

    iDigital Forum Resident Thread Starter

    Hi, I am not sure, I will decide that later
  25. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Just keep in mind, that once you go south of about 18-Watts in an SE amp, that you will really need some sensitive speaker's to make the whole thing work.

    Once you start getting down to the 8-Watt 300B class "A" SET amps, you are going to want to have speaker's with 96-98 dB at a minimum.

    Even then, remember, with a 8-Watt amp, you will need about five of those eight Watts to cover the low frequencies. No matter what amp and main speaker's I use, I still have a sub in the system.

Share This Page