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Tube Power

Discussion in 'Amps and Cabs [BG]' started by jackcregg, Aug 27, 2007.


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  1. jackcregg

    jackcregg Guest

    Feb 25, 2007
    I was reading a thread on here about whether someone should get a warwick tube path 10.1 or an ampeg svt something or other.

    Someone then posted that they would have the same overall volume but one would distort harmonically and the other not so harmonically.

    So i was thinking if a tube head is rated at 300 watts it can pump out the same volume as 1000 ss. So could a tube amp at 300 watts run through a 300 watt speaker and still kick out the same amount of power as 1000 ss
     
  2. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile
    1000 watts is 1000 watts and in lab tests you can bet the SS will win.

    BUT!!!!

    as far as usable volume and such, my 400 watt tube head gets louder than my old Crown CE1000e could.

    ...and sounds better to my ears doing it.
     
  3. Call me crazy - but I think either would be quite capable of blowing that 300w speaker away.

    Tube heads are definitely louder than SS stuff - but SS heads are cheaper, most often lighter and cleaner in sound reproduction.
    The difference is how they distort - tubes amps tend to distort gradually and break up into 'overdrive' - without a pedal.
    That said - tube amps are not made equal. Some break up earlier than others, and some can be comparatively clean at high volumes IME.
    A SS amp will simply clip and sound awful if you run it to hard, IF you don't have enough headroom that is.

    It's kinda up to you - you wanna run an old-school overdriven sound or "sterile as chenobyl" clean?

    smo
     
  4. jackcregg

    jackcregg Guest

    Feb 25, 2007
    possible siiigggg
     
  5. bassbrock

    bassbrock

    Feb 20, 2007
    Callahan, FL
    So, is clipping a tube amp's power amp stage similar to clipping a solid state power amp?

    Meaning, that without a clip limiter, a solid state power amp will output more power than it is rated when clipping. Will a tube amp do the same thing? That could possibly account for the loudness issue.
     
  6. chaosMK

    chaosMK

    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    I'd get the SVT.
     
  7. I'm no expert; But no and no.
    PBG is the resident scholar on this stuff - he knows it SOOO much better than me.

    IMO once you start clipping a SS amp - it sucks.
    But if your SS amp is powerful enough you won't ever need to worry.
     
  8. bassbrock

    bassbrock

    Feb 20, 2007
    Callahan, FL
    My questions was concerning more of the electrical side of the equation, not the quality of sound.

    When you clip a SS amp, it can actually output more voltage that it is rated for, especially in bursts. Soundwise, yeah it sounds horrible.

    Does a power tube amp do the same thing? When it is overdriven or clipped, does it physically output more voltage than the tube is actually rated for?
     
  9. seamonkey

    seamonkey

    Aug 6, 2004
    It won't put out "more voltage"
    If the power supply rails are 50v, then the most it can put out with a clean sine wave is 50v. If you sent it into full clipping and it resembles a square wave - it'd still be 50v. The power supply will likely sag and it will actually be less than 50v. Power wise, wattage can increase but it can't go over twice the RMS sine rated wattage.

    If you're smart about it, and start to sound bad when you clip but need the volume, turn down the bass and treble. Turning down the bass will allow more power for the mids, and cutting the treble will cut down any harshness that leaks through from your input signal as most of the extra high freq harshness you hear at clipping comes from the input signal.

    Some powered speakers actually do this on their own. Goes along with loudness contouring.
     
  10. bassbrock

    bassbrock

    Feb 20, 2007
    Callahan, FL
    So perhaps the perceived loudness difference in tubes vs solid state is the compression that occurs in an overdriven or clipped tube?
     
  11. Yes, natural tube compression plays a role, as does the fact that a clipped tube power section still sounds musical to the ear. SS clipping is something that your ear will want to avoid altogether.
     
  12. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    When a SS amp clips, as previously stated, it chops off the top of the sine wave cleanly resembling a square wave. The harmonics of a square wave are predominatly odd. A tube amp on the other hand clips with a more rounded top. This gives even harmonics that sound less odious to the ear. Now you know why most guitar players prefer the sound of tube amps.
     
  13. seamonkey

    seamonkey

    Aug 6, 2004
  14. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    Here we go again. :help:

    Lets not get into the debate about Tube vs. SS watts or the reasons people believe one way or the other about said watts and perceived volume. If it continues to go that way, this thread will be closed. Capisce?
     
  15. jarrod cunningham

    jarrod cunningham

    Apr 24, 2007
    sylacauga alabama
    spector basses
    i know this holds no scientific value at all , but i was told by a very reputable old school amp builder that a tube amps rated wattage multiplied by three (ie 300w x 3 = 900) would be equal to the wattage of a solid state amp whos power rating is equal to the sum of the equasion . basically saying it would take a 900 watt solid state amp to keep up with a 300 watt tuber .....
     
  16. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    A CLARINET SOUNDS PLEASING!!!!!???? Just kidding! I am absolutly sure that sound from an oscillating reed will be a sine wave. I think you're wrong on that one but so could I. The harshness is ALL about clipping. I read your Rane article which is basicaly about preventing clipping by attenuating the input if is suffucient to couse the amp to clip. This is the same as turning down. If a SS clips it cannot give any more output however much you turn it up. If you have a perfectly clean signal coming in you will have a perfectly clean signal comeing out of the amp ( in theory - no amp is perfect ). As soon as as the amp starts to clip tha's all she wrote and it will sound terrible.

    To Reply to Kelly, I don't think this is about which is better tube or SS. I use a SS power amp but I drive it with a pre-amp with a tube in it. I LIKE having a tube in the chain somewhere but that is a personal preference nothing more. Would I use a totally tube amp - absolutely but I would like a roadie to carry it.;) The choice SS or tube is precisly that: a choice. If your like what you are hearing from your rig then that's what you should use and enjoy.

    Bassrocker, as a person who has been designing and building tube electronics for close to fifty years, I think you might have misunderstood what your old school guy meant. 300W clean from either SS or tube is still 300W and will not sound any louder. Now if you said that to keep up with a guitar player using a 50W tube amp a bass player would need 500W (and the speakers to handle that power) then that would be a fair assessment
     
  17. A9X

    A9X

    Dec 27, 2003
    Australia
    Lots of guitar amps have 2 or more extra high gain stages in the preamp that do a lot more to affect the tonal structure than the poweramp, many of which in tube designs aren't all that far apart design wise than the recommended designs in the datasheets and manuals of the era for hifi amps.

    An SS amp, depending on the design, will generally sound quite bad long before the output waveform resembles a square wave. Tube amps will clip 'softer', ie usually with a more gentle transitional waveform, which has more even harmonic content and is more sonically benign. A couple of other things to remember is that as NFB is involved, and when an amp clips, the NFB loop isn't effectively there anymore (run out of gain for correction) most tube amps will generally sound a lot more pleasant to listen to due to better inherent linearity and lower gain. Most tube amps are under specced in terms of output transformers, so when they saturate, they lose inductance, therefore LF response suffers, less gain at LF, less NFB etc. All this is happening dynamically so it doesn't show up in simple distortion tests or on a CRO but will on something like an Audio Precision One. Makes for a built in compressor.
     
  18. A9X

    A9X

    Dec 27, 2003
    Australia
    I've been building tube gear since my teens, or about 30 years and am an EE. Just got a superb winder so I'm going to build 2 >400W (real watts, not MI advertising watts) of different designs as I have all the rest of the parts. Just waiting in the huge M6 cores to arrive, and an old retired gent I know and respect to find some time to help finalise the designs of the OPT's.
     
  19. seamonkey

    seamonkey

    Aug 6, 2004
    There are zero feedback SS amps. And here's and affordable module if you're interested:
    http://www.lcaudio.com/index.php?page=31
    I doubt it sounds any better or worse than a well designed SS amp with feedback.

    And really severe clipping is just a fringe case. Modern SS amps deal with it fine. They don't loose feedback control.

    Clarinets really are square waves. And I like the way they sound. :) The applet I pointed out will let you draw a square wave by just following the harmonic template and it sounds like a clarinet. Try the same with even harmonics - you'll see a waveform that resembles crossover distortion. In any case, even/odd harmonic stuff would have more to do with the amplifier topology than the devices.

    As far as the Warwick tube path goes. It's a complete tube amp, including transformer and load. Followed by a SS power amp stage. This would be like taking a tube amp, and a DI off the speakers then running it through a FOH amp. Seems like this would satisfy any one inclined to non-SS amps. I don't think any modern big name act doesn't run through FOH systems.
     
  20. A9X

    A9X

    Dec 27, 2003
    Australia
    I've not tried these but have used several other class A zero NFB SS designs. I mainly use, and have done for many years, zero NFB tube designs, though I'm currently working on a shunt feedback pentode class A PP amp that is sounding and measuring superbly. NFB taken from the plates of the output tubes back to the drivers.

    I've had an interest in audio and perceptions for a long time, and zero NFB, high inherent linearity designs almost always sound best to me.

    When I get some time, I've got some of the LC Audio Zappulse modules and plans on a hybrid biamp head.

    I was adressing tubes mainly before as the output transformer, even absolutely superb designs, ie not MI amps, are severly limited by the amount of NFB that can be be wrapped around them. Tube designs are usually gain limited, or gain stage limited. Not an issue with SS amps, providing they're designed well.

    A highly recommended read on this subject (if you're interested) would be Norman Crowhurst's excellent articles on feedback. They're available online

    It's a better way to implement it and closer, but doesn't account for output impedance, reactive loads of speakers, NFB etc. I'll probably implement something similar with my hybrid head mentioned above. The output of that little power stage and transformer would also make an excellent line driver/DI too. Two birds...
     

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