I'm looking for info about tube amps

Discussion in 'Archived Threads 2001-2004' started by Jereme D, Apr 13, 2002.

  1. Jereme D

    Jereme D Stunt Coordinator

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    I catch bits and pieces here about how great tube amps are supposed to be. I'd like some links to sites with basic information about tube amps and how they work.
    One thing that usually leaves me scratching my head is how they can use so little power. I've run across a few on Ebay and Audiogon that boast numbers of watts down into the single digits and low doubles. I'm curious why I need a receiver with 100 watts of power per channel when these little things (That frankly look like a bunch of junk attached to a base [​IMG]) need only a few. I'm familiar with the concept of headroom, but how do tubes compensate?
    Some other questions I have:
    What exactly are the tubes? What's inside of them?
    Do you still use a normal pre-amp with tubes?
     
  2. John Sully

    John Sully Stunt Coordinator

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    Let me preface this by saying I am no fan of tubes.
    Tubes are the oldest form of signal amplification having been invented in 1906 by Lee DeForest. A tube consists of an anode, a cathode, a grid and a heater element. The heater is used to stimulate electron emission from the cathode and the resulting flow of electrons in between the cathode and the anode is modulated by a signal which is applied to the grid. The anode and cathode typically operate at very high voltages and the signal applied to the grid is a fairly low voltage. The result at the output of the tube is an amplified version of the low level signal applied to the grid. Tubes have different operating characteristics at clipping than transistors and this results in large amounts of the second harmonic in the distortion spectra, especially in class A circuts. Because of the large amount of second harmonic in the distortion spectra of tube amps many people find their sound preferable to solid state amps, refering to the sound as "warm".
    Tubes are perfectly capable of delivering large amounts of power with good linearity, just as solid state amps are. There are many examples of high quality tube amplifiers from the 50's and 60's which delivered 60 to 100 watts of clean power. Indeed if such amps did not exist the acoustic suspension speakers which were so popular in the 60's and on into the 70's would not have been practical. Today the rage in tube circut design is called the single ended triode, which is basically the simplest and most primitive circut which can be used for amplification. Amps of this basic design are hard pressed to produce more than a few watts of power -- many are just 2 or 3 watts -- and need to be paired with very high efficiency horn speakers in order to obtain acceptable listening levels. Typically a speaker these days is considered very efficient if it gives an output level of 90db/1 watt/meter. For contrast many speakers used with modern tube amps approach or exceed 100db/1 watt/1 meter, the equivalent of increasing your amplifier power by a factor of 8 or more.
    The reason some people feel that tubes sound better is because of the different characteristics when the amp goes into a non-linear operating state. The result is a sound which is often referred to as "warm" or "musical". However, IMHO, an amp should never be operated in it's non-linear range, so the clipping characteristics of the amp should not come into play. That said, multiple ABX (double blind) listening tests have shown that when operated in a linear fashion, without clipping, there is no discernable difference between tubes and solid state amps. (See www.pcabx.com and True Audio)
    So that's my dissertation on tube amps and why not to bother with them. I'm sure that others will disagree [​IMG]
     
  3. Duke H

    Duke H Stunt Coordinator

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    I agree that tube amps have their downfalls. On the other hand, it has already been noted that one reason many people are drawn to them is their "warm" tone...right or wrong, it is what it is. I will say, though, that I have A solid state Yamaha HTR-5560 (RX-V630), as well as an old hand-Built Tube Amp. I use the tube amp to drive a set of 12" 3-way floor cabs. It gets around 75 clean watts per channel, and sounds pleasing when used in conjunction with my turn table. Maybe I "tolerate" tubes because I'm a guitarist (making me difficult, egotistical, and pretentious)...I don't know. All I've gotta' say is that both formats have their place.
     
  4. chung

    chung Stunt Coordinator

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    Jereme:
    Just want to add something that is probably obvious to most of us: tubes need to be warmed up. Tubes have a relatively short life-span also, so you don't want to leave them on. When tubes age, their sound changes, so when you put a new set of tubes in, you may not like the new sound. Some people like the glow of the tubes, though [​IMG]
     
  5. Martice

    Martice Screenwriter

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    But when tubes are good..they are real good.[​IMG] I used to own a Sonic Frontiers Line 1 tubed pre and until this day it has given me the best 2-channel performance that I've ever had in my home. Unfortunately I had to get rid of it because the wife didn't like having to go through the HT bypass in order to get to the processor just to watch a movie. Go to Audio Asylum becaue they have very healthy discussions about tubes over there. No matter what I put in my system as a pre/processor has ever come close to giving me the joy that my tubed pre amp gave me.
    Good Luck
     
  6. Jereme D

    Jereme D Stunt Coordinator

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    Thanks for all of the great info. :) I have a few more questions if anyone wants to have a go at them....

    Are normal pre-amps used with tubes or is there some special kind of pre-amp made specifically for them?

    What kind of upkeep is involved with tubes? I'm assuming the glass tubes themselves 'burn out', because I've seen replacement tubes on ebay.

    Are tubes a DIY thing for the most part? As I said in my first post, most of the ones that I've seen just look like a bunch of junk attached to a base.

    Thanks again!
     
  7. Martice

    Martice Screenwriter

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    Hi J. I really think that this may be the wrong forum for you to find the answers for what you're looking for. I've included this link and this link to get you started.
    All of the information that you could ask for are located on these sites. I personally had a tubed preamp and a solid state power amp. Sort of a hybrid setup. I think this is the way to get a BIT of both worlds where as you get the desired distortion affect that tube advocates love and the power and control that solid state advocates love.
    Some people do build their own tube gear but many companies that range from budget (AMC for one) all the way up to the 'highend offerings from McIntosh, Conrad Johnson, Sonic Frontiers etc. are all sold just like any other solid state gear you may find in your friendly neighborhood audio store.
    If you are seriously planning to go the tube route, I strongly suggest that you do some lurking in the two sites that I left for you and research. No matter the draw backs of tubes, many people feel that it's worth the up keep requirements just like an auto hobbiest loves to work on his car or even some solid state audio lovers like to tweak their system. One major plus for tubes is that depending on how much you get into rolling your tubes (you'll find out what that means once you do some research), you'll start to see that for once you get to have at least some input into how your tubed gear sounds depending on what tubes you choose. Something that solid state gear will never allow you to do unless you use the bass & treble which to me is not the same thing.
    Take a look at the links I gave you and soak it up but be careful because they say "tubes are like honey and if you have a sweet tooth you might get hooked".
    Good Luck
     
  8. Saurav

    Saurav Cinematographer

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  9. Jereme D

    Jereme D Stunt Coordinator

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    Those two links look good Martice. Especially the second one. I will read those to get up to speed. Thanks.

    Ultimately, I will not be able to get tubes. At least not right now as they are quite expensive.... Even the used ones that I've seen.

    I'm going to try to find someone in my area that has some running so that I can listen to them. Unfortunately, the electronics stores around here don't carry anything remotely non-consumer grade, so I can't hear anything there.

    Saurav - I am not really concerned about numbers. Only the sound. By the standards here, my system is very low grade. I think it sounds great, though.

    Onward to the research-mobile!
     
  10. Rich H

    Rich H Second Unit

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    Jereme D,
    I'm no tube apologist; I use both tube and solids state amplification.
    I'm also no anti-double-blind-test subjectivist (only believes his personal impressions, not what tests/specs/engineers tell him). I use some double-blind tests myself.
    But...but..but...as wonderful, clean, sharp, extended and dynamic the sound of a solid state amplification-driven system can be, I'm often shocked at how synthetic it can sound next to the same system driven with (an appropriate) tube amp.
    What some tube-amp-driven systems capture (or impart) is that illusive "organic" quality to voices and instruments
    that seems missing from most hi-fi systems.
    A voice through a tube amp is often more able to sound less hard-edged, less balance, less "spiky."
    The result for me are more "human-sounding" humans, and a more believable sound on many different counts (the overall sonic presentation is less constricted sounding, less stuck-in-the-speakers, and more relaxed - relaxed in the way that is analogous to how I experience real organic sounds. In contrast, many sound systems sharpen and harden familiar sounds, which tends to put me on edge).
    Just one guy's take.
    The best thing you can do is find a tube amp and take it home to compare in YOUR system. That is were you'll most easily discern the difference tubes can make. Since you want to experience "tube sound," try finding a brand known for the tube sound. Suggestions are: Conrad Johnson, Cary,
    VTL.
    Or to start cheap you can find an old Dynaco Stereo-70 tube amp. Many people begin with the Dynaco because they can be found fairly cheap second-hand and it gives large dollops of the tube magic. Here's a link to people reviewing the Dynaco at audioreview:
    http://www.audioreview.com/PRD_116296_1583crx.aspx
    Also, Antique Sound Labs is making VERY affordable tube amplification. Check out both push-pull and single-ended type of tube amplification too.
    Have fun,
    Rich H.+
     
  11. Saurav

    Saurav Cinematographer

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    Expensive... what's your budget? Like Rich said, you can get a very competent ASL tube preamp for about $400. Or you can build yourself a Bottlehead Foreplay from a kit ($150 for the basic kit, $300 with all upgrades) that is said to be as good as several commercial units costing in the multiple thousands. I built a Foreplay, and while I cannot compare it to $2K - $3K preamps (I haven't heard any), I know it sounds much better than any $300 preamp I've heard (and I've heard a few).
    Rich, that's a very good description of what tubes sound like, IMO. More natural and lifelike, that has been my experience too. I would take an extra few % THD for that, any day. I have a very subjective definition of 'accuracy' anyway [​IMG] My definition of 'more accurate' is 'sounds more like the real thing'.
     
  12. Martice

    Martice Screenwriter

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    Dianne Reeves has never sounded the same since I got rid of my tube preamp. I will venture back into tubed electronics again and it can't be soon enough. However, I think I'll stick to Solid State with HT.
     
  13. Larry B

    Larry B Screenwriter

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    Rich:

     
  14. Aslam Imran

    Aslam Imran Second Unit

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    Here are some of the differences IMO that make tubes sound different from transistors:

    Tubes have even ordered harmonic distortion that is not harsh sounding as all the natural musical instruments excite even order harmonics and our ears are attuned to these harmonics, so there is no listener fatigue.

    Transistors have odd order harmonic distortion and no musical instrument excites odd ordered distortion so our ears hear this distortion as dissonant and this leads to listener fatigue.

    Tubes have lower slew rates (except the SET) so bass is weaker with tubes.

    Transistors have very high slew rates and hence have snappy bass.

    Tubes go into soft clipping so even when a tube amp is driven hard and is clipping it doesn't sound harsh to the ears.

    Transistors go into hard clipping, so if a SS amp is driven to clipping it will sound harsh.

    Tubes (and this is my own observation) give music better holographic dimensionality while transistors sound collapsed. I am sure most would disagree with the last statement.
     
  15. Aslam Imran

    Aslam Imran Second Unit

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  16. matthew_rm

    matthew_rm Second Unit

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    For info on tubes, check out the Klipsch Forum at www.klipsch.com (go to 2ch audio.) You should learn lots there to.
     
  17. David J L

    David J L Auditioning

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    To address another part of Jereme D's question,

    You can mate a tube amp with a solid-state preamp if you want to. Likewise, you can mate a solid-state amp with a tube preamp (which I may do when my old preamp finally gives up the ghost).

    Some say that a SS amp with a tube preamp gives you the best of both worlds: slammin' bass from the amp, and refined mids and highs because of the pre. But I am sure that finding a well matched, synergistic amp and preamp are the key to working this magic.

    And as all here probably agree, stick with all solid-state for your theater.
     
  18. John Morris

    John Morris Guest

    I am just starting to get into tubes, starting with an ASL Headphone amp. I will admit, that "tube rolling" sure is alot of fun. It is just amazing how differently the same amp can sound just by switching one tube. I don't know what to call the different type tubes, but so far, I have tried 5 different "tone altering" tubes and a different pair of output tubes. Of course, the tubes that I like the best are all NOS (new old stock) tubes from back as far as the 70s. Of course, these tubes are also the most expensive to buy. Supposedly, the very best tube for this amp is a NOS from the 1950s. If you can find this tube, it runs about $70 or more...

    Just based on what I've been able to learn so far, and already knowing the type of sound that I like, my guess for a future dedicated two channel system would include a tubed preamp and a SS amplifier.

    PS - and yes, my tube rolling is all done in DBT style.
     
  19. Saurav

    Saurav Cinematographer

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    How do you do that? Do you get someone else to switch the tubes while you're not looking?
     
  20. Ken Situ

    Ken Situ Stunt Coordinator

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    The easiest way to start a tube setup is to get your hands on a Dynaco ST 70, Mark III, or Mark IV, and a Dynaco PAS III tube preamp, and you're set for a long time.

    These setups can be very cheap, and last for a very long time.
     

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