The advantages (and disadvantages) of using the 211 broadcasting triode in stereo amplifiers

Discussion in 'Audio Hardware' started by Steve Hoffman, May 26, 2020.

  1. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    For the few of you that might be interested, I was asked: "Why use a giant, dangerous 211 triode tube in hi-fi audio? The answer is in one name. Kondo-San.

    My colleague Srajan Ebaen from 6moons.com has your answer.

    Kondo-San of Audio Note. Specifically, his supreme creation, the Ongaku amplifier, which was treated as an icon and reference. Now why the 211? Simple. This tube was very cheap in the 1970's when the US army sold out its spare parts reserves. Remember, there were big US storages in Japan. So, those warehouses of the US signal corps were a good source for cheap but excellent tubes. Only a few dollars per tube.

    Originally designed for radio broadcasting transmitters, the 211 has excellent linearity. This lends itself to an audio amplifier with no feedback (neither local nor global) but still low distortion. Lack of feedback made for a very musical sound. Due to its pure graphite plate, the 211 also offers a big maximum dissipation of 75 watts. That made it possible to build a Class A single-ended amplifier with 27 watts of output power, quite substantial for this concept.

    The 211 triode has low output impedance. It limits maximum gain but makes the amplifier a voltage, not current source. (Pentodes need the feedback loop to compensate for their high impedance.) Another feature was the thoriated Tungsram cathode - delicate but with a long life approaching 10,000 hours. And lastly, it has a sexy look.

    BUT the 211 also has certain limits.
    • Very high plate voltage of 1000 - 1250V. It is very difficult to make a good power supply for this voltage range. There are no large enough capacitors for these voltages so it is necessary to use two (as in the Ongaku) or three high-voltage power supplies connected in series. The output impedance of high voltage supplies, their hum and reliability are worse than for power supplies of lower voltages. Many sonic aspects such as impact, control, space and focus are intricately connected to the power supply quality.
    • Another problem exists with the output transformer. As peak voltages on the primary exceed 2500V, all the insulation must be thicker than usual. The distance between the wire windings increases and magnetic coupling diminishes.
    • Because this output transformer must have a high primary inductance, it limits bandwidth. High inductance combined with high capacitance between the turns creates a self-resonance close to the audio band.
    • The 211 is difficult to drive. To obtain full power from a 211 or other transmitter tube, you need a positive grid voltage relative to the cathode. In this mode, the power tube needs not only voltage but also current. Drive power can be a few watts as in the Cary CAD-805 but the bigger problem is with the DC drive signal. It is not possible to drive a 211 with capacitor coupling. You need another transformer for driving it as in the Audio Note UK Peter Qvortrup version of the Ongaku; or a DC-coupled cathode follower as in the original Kondo Ongaku.
    But let's back up for a moment. Just what is an SET (single-ended triode) amplifier? It's a vacuum tube-based design that uses a single-triode tube per channel to produce output without splitting the musical signal's plus/minus parts in each channel. In contrast, a push/pull amplifier, which uses a pair (or more) of tubes, splits the plus/minus of the music signal, then it has to put them back together to form the complete musical wave in each channel. Many argue that, once you split the signal's plus/minus, you never quite put it back together again with the exact purity that it contained beforehand. This is technically referred to as a crossover distortion, which ironically doesn't have anything to do with actual speaker crossovers. Also, almost all reference-level SET amplifiers run in pure Class A, not AB, to further avoid this type of distortion. The perceived high sonic quality is mainly attributed to the simplicity and minimalist approach of the circuits involved, as well as the triode vacuum tubes that are typically used. One SET aficionado describes it as "a Zen simplicity to reproduce the complexity of music. Less is more." Of course, as with any other amplifier, an SET's overall build quality, the type/quality of internal parts, and the power supply will define how well it performs. For an SET design to fully live up to its potential, its transformers (core material, type of wiring, mastering of hand winding, isolation/shielding) must be of the highest quality; otherwise, the amplifier will roll off the top-end frequencies.

    The most popular SET amplifiers use three types of triode tubes: the 45, which produces around two watts per channel; the 2A3, which produces around five watts; and the 300b, which produces around eight watts. In 1906, an American engineer, Lee De Forest, invented the prototype triode tube. A triode tube has three internal parts (filament/grid/plate). Even though the 45 and 2A3 were manufactured back in the 1930s and '40s, many NOS (new old stock) tubes are around because so many were produced for all types of devices, including radios. The 300b tube, meanwhile, was invented and manufactured by Western Electric for its movie theater amplifiers in the 1930s and '40s. The original tubes are now very rare and can cost thousands. The professional broadcasting triodes (211, 845) came into high fidelity in the 1970s in the Far East.


    So there you have it. My Audio Note UK 211 amplifiers (I currently have the Copper Jinro integrated and the Silver Ongaku Kensei) need a good deal of smart design to make the 211 shine. But when it does, what a glorious sound!

    Photo: New Audio Note UK AN-4242e 211 type valves. Photo credit: Steve Hoffman

    audio note photo by me.jpg
     
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  2. AudioAddict

    AudioAddict Forum Resident

    Location:
    USA
    Very clear, helpful, and accurate. Please keep them coming.
     
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  3. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    Glad it was interesting to you..
     
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  4. AudioAddict

    AudioAddict Forum Resident

    Location:
    USA
    So I'll bite...
    Am using 300B monoblocks rated at 10 watts per block into Tekton Double Impact speakers rated at 98db efficiency (and accurately so). Have plenty of volume. My system is setup so I can switch to powerful Emotiva XPA-1 monoblocks with high-bias class A (60 watts) and A/B up to 1000 watts (at 4 ohms the speaker rating). When I switch back and forth I note that the SS amps are much fuller, have certain advantages in bass frequencies, and are effortless at all volume levels. By conbtrast, the SET amps are much more timbrally accurate and their instrument portrayal has a certain natural and continuous quality that wins over SS.
    SO(2) what is the sonic advantage of 211s over 300Bs? Would guess from the above that the FR might be more secure but I am measuring my 300Bs with REW and they EQ out to perfect from 16-20k with not too much change.
    When you say "Dangerous" do you mean explosions? My cavalier spaniels enjoy a good fire...
     
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  5. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    I've not heard any of your gear but I'd say your 300b's are putting out 8 watts on a good day. Sometimes that's not enough, even with high efficiency (sp?) speakers. My powerful tube amps are full bodied (McIntosh, Marantz, Fisher, etc.) but they don't have (as you say) that "certain natural and continuous quality." It's just a choice. That's why I have both. With my Audio Note speakers, my higher powered tube amps sound great but don't reach out to my like my 211 AN amps do.. Stereo is just an illusion so you have to decide which illusions please you more, I guess.

    Sonic advantage of a 211 over a 300B? More authoritative sound for the most part. I don't have any 300b amps any more but I did enjoy the tone of the tubes. The 211's have that same even tone, but more, since the watts are higher..

    They need big voltages to work. Best not get in the way or you'll be fried like an egg..
     
  6. caracallac

    caracallac Forum Resident

    Location:
    Ireland
    Those big transmitting valves in the right circuit can deliver a sound like nothing else, all the benefits of a simple single ended design with the ability to drive almost any speaker you care to use. Unfortunately though, they are not something that can just be installed and forgotten about. The heat generated and the voltages involved are rarely seen in domestic appliances other than large ovens and mean that the designers and manufacturers really need to know what they’re doing as does anyone servicing or even using the amp. In short, anyone who is in any doubt about their ability to use and maintain such a beast, protecting it from children, pets and accidental damage would be well advised to look elsewhere. But those lucky people who can dedicate a room to their system and give it what it demands can enjoy the truly exceptional.
     
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  7. inperson

    inperson Senior Member

    Location:
    Ohio
    Didn't you say years ago you have a good stash of 211's? Do you favor the old 211's over the new ones or both just as good?
     
  8. NapaBob

    NapaBob Forum Resident

    Location:
    Napa Valley CA USA
    The is a lot of variability in the older ones, but when they are good, they are very good.
     
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  9. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    I do, RCA Radiotrons, GE VT-4-C's and Elrogs, Psvanes and the best of them all, the AN4242E's. I'm set.
     
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  10. Jim Hodgson

    Jim Hodgson Galvanically Isolated in Greenpoint

    Location:
    Brooklyn, NY
    In one of the early issues of Joe Roberts’s Sound Practices, Kondo-san wrote an article about the Ongaku. Although that was almost 20 years ago, Enjoy the Music continues to host the article here:

    Audio Note Ongaku Article by Hiroyasu Kondo, Audio Note Japan Sound Practices Magazine Online

    I figured it may be of interest to folks reading this thread—especially anyone with his sights set on designing with transmitter tubes, which I agree is not for the faint of heart (literally or figuratively).
     
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  11. caracallac

    caracallac Forum Resident

    Location:
    Ireland
    The nicest 211 I ever heard came in a box stamped “US Army Signals Corp”
     
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  12. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    That article is what began it for me.
     
  13. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    Either RCA or GE.
     
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  14. AudioAddict

    AudioAddict Forum Resident

    Location:
    USA
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  15. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    Forgot I even started this thread. The Mighty 211 (VT-4-C). God's tube.
     
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  16. SandAndGlass

    SandAndGlass Twilight Forum Resident

    To those who want to get real close, but are not quite in that league financially, consider a product like the Line Magnetic and the 845 tube. It operates at a lower plate voltage (not by much) and the transformer requirements are less.

    OEM tubes are unobitanium but new modern tubes are in the $100 range (and up). :)
     
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  17. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    Bumped by request
     
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  18. saturdayboy

    saturdayboy Forum Resident

    Location:
    Chicago
    I’m running a single ended 300B amp into 95 db 12” coaxial speakers and it’s more than loud enough for my living room, yet I’m still intrigued by the 211 tube. Can someone talk me out of it? (or into it?)
     
  19. allied333

    allied333 Audiophile

    Location:
    nowhere
    I believe it is best to refer to the 211 tube as an HF (high frequency) triode. It was not exclusively used in broadcast transmitters if ever used in that application. It was definitely used in HF transmitters and likely most in WWII military transmitters.
     
  20. jusbe

    jusbe Modern Melomaniac

    Location:
    Auckland, NZ.
    They cost a lot of money to do well. High voltages. High transformer quality and large size.
     
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  21. allied333

    allied333 Audiophile

    Location:
    nowhere
    GE 211 are about $500 used and $800 new. New Chinese 211 are $120. It requires about three 300B tubes to make same power as a 211 so the 211 are not too expensive for a triode in its power range.
    I would like to own a 211 SE amp, but the cost..........
     
  22. WvL

    WvL Improve the lives of other people

    Location:
    Birmingham al
    Great thread. thank you. Loving my 211 powered New Audio Frontiers stradivari 211S amp. The speakers are almost through with their initial break in. :righton:
     
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  23. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    Can you post photos of your amp?
     
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  24. WvL

    WvL Improve the lives of other people

    Location:
    Birmingham al
    [​IMG]
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    Audio rack to better organize the gear is on order
     
    Last edited: Jul 9, 2022
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  25. drmoss_ca

    drmoss_ca Vinyl Cleaning Fiend

    Location:
    NS, Canada
    Audio Electronic Supply (the now defunct kit division of Cary Audio) used to make 811 triode SET monoblocks. Rumour had it the 811 was designed for the radio in the MIG-25 Foxbat, but that might have been marketing at work. They were very sweet and made something like 12 or 15W. Wish I still had them sometimes. Certainly true that broadcasting tubes can sound wonderful!
     
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