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Tube Watts = SS Watts ??

Discussion in 'Amps and Cabs [BG]' started by Llewellen, Oct 22, 2019.

  1. Llewellen

    Llewellen Guest

    Dec 23, 2016
    A reputable cab maker told me recently that 50W from an all tube amp head is the equivalent of about 300W from a SS head. That seemed odd to me. I'm not an EE but it seems to be that, measured at the output of the amp, Watts are Watts. Or was he perhaps meaning to refer to damping factor?
  2. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    I usually don't lead with this. But this time it will save you some grief.

    Do a search. There are dozens of arguments *cough* threads about this. :D
  3. Llewellen

    Llewellen Guest

    Dec 23, 2016
    I did a search. The search function on TB is a very blunt instrument and returned a myriad of hits about everything tubes :)
  4. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    The shortest version that seems to be somewhat of a consensus is as follows (and I'm sure I'll get something wrong).

    With solid state, that maximum output is a hard figure. If you try to go past 500 watts of output on a 500W amp, you can damage things. And the sound usually isn't pleasing anyway. With tubes (and the rest of the circuit, including output transformers and whatnot) you can push them "past" their rating somewhat into a distorted tone (not an angry tone yet but something a little wooly) that is still pleasing to many ears. In the view of some, it's not "past" it's rating, rather the extreme highest output of a tube amp sounds a lot better than the extreme highest rated output of a SS amp.

    It's a perception thing.

    So watts are watts. However, the PERCEPTION is that a 30W tube head is a lot louder than a 30W SS head simply because up at the highest output levels of a tube amp the sound can be pleasing and it usually won't damage things.

    These waters are murky at best, and like trying to navigate through drying concrete at worst.

    Short version: There is no equivalent tube to SS power rating of watts.... like the 50 to 300 ratio your tech claims simply isn't true. But, to many, the perception is that (all else being equal in the signal chain) a 100W tube head will get a lot louder than a 100W SS head. In general, it seems that you can squeeze a bit more volume out of an equally rated tube amp because of how the circuit reacts to everything else in the chain.

    Hope that helps.
    Last edited: Oct 22, 2019
  5. I would suggest that cab maker isn't all that reputable. Or shouldn't be.
  6. dramatwist


    Sep 27, 2019
    ...I dunno... I'm no expert, but I've owned little 5-watt amps that "seemed" way louder than a 50-watt Bassman... go figure...
    Jeff Scott, bassballs27 and Zbysek like this.
  7. Well, you are no expert as opposed to a reputable cab maker.

    I would suggest the 5-watt amp was probably solid state and the Bassman, of course is a tube amp. If you are talking clean, pretty much anything is louder than a 50 watt Bassman.:D
  8. bassdude51

    bassdude51 "You never even called me by my name." Supporting Member

    Nov 1, 2008
    Central Ohio

    Watts is watts is watts is watts. Whether if it is tubes, SS or nuclear. Watts is watts.
  9. Llewellen

    Llewellen Guest

    Dec 23, 2016
    Thank you.
    bobyoung53 likes this.
  10. Llewellen

    Llewellen Guest

    Dec 23, 2016
    I was surprised also but there are several people on this forum who use his products and extol their virtues.

    I decided to pass when he also told me I could design my own cab dimensions and driver placement without affect the T/S alignment for the drivers he uses.
    GregC and JMarkD like this.
  11. seamonkey


    Aug 6, 2004
    A 3kg Solid-State amp will blow a 3Kg tube amp off the stage!
  12. For future reference when trying to research a topic, type the information in google followed by site:talkbass.com. example:

    tube watts solid state site:talkbass.com

    Much easier to surf the site that way. Hope you find your answer!
  13. McFarlin

    McFarlin Supporting Member

    Oct 27, 2011
    Austin, TX
  14. higain617


    Sep 12, 2013
    Watts are watts. There is no difference in volume between an SVT and TC Electronics 300W head. No irony in this post at all.
    pcake, murphy, Dr Gero and 3 others like this.
  15. GrapeBass


    Jun 10, 2004
    Graphic designer: Yorkville Sound
    All watts are not created equally.

    Manufacturers typically use whatever their marketing department wants.

    Watts... RMS vs Peak / Max
  16. micguy


    May 17, 2011
    A tube amp can be run further into clipping than a solid state amp before it sounds bad. Therefore, a 100 watt tube amp will play somewhat louder in a band context (where it's just transient peaks clipping) than a 100 watt solid state head before you notice that it's distorting. Will it go as loud as a solid state amp with twice as much power before it gets ugly? maybe. 6 times? probably not.
  17. Balog


    Mar 19, 2009
    Mukilteo, WA
    Watts are an empirical measure, and are the same regardless of the source.

    Amplifier ratings are kind of empirical measures, but have a huge marketing factor in that there are a lot of ways they can be measured. Some amps have listed wattages that represent what they can achieve for a fraction of a millisecond before you trip the breaker and the amp catches fire.

    Ratings, even when done honestly and in accordance with best practices, are only for a specific amount of signal distortion. Tube amplifiers tend to output significantly higher wattage than their rating in actual use because people like the way they sound when distorting. People tend to not like the way solid state amps sound when outputting more than their maximum rating and distorting.

    Human hearing and amplifier output is not linear with regards to frequency. Certain frequencies are detected easier than others, and higher frequencies are easier to reproduce than lower. So an amp that is strongly voiced to those frequencies most readily detected will seem louder, regardless of actual SPL.
  18. There's more harmonic content in a tube-amp's output. It's almost like bandwidth. The tube-amp just has more bandwidth within the same amount of Watts.
    It's why tube-amps naturally have a more rich timbre.
  19. Wasnex


    Dec 25, 2011
    This is a good generalization. In my experience, some solid state amps sound fine pushed into OD and many tube amps don't/can't actually make their claimed power unless they are pushed into OD.

    In order for a wattage rating to be meaningful it needs to be accompanied by a distortion figure. For example the power for tube amps is often cited at 5% THD, which is relatively clean, and 10% THD which is perceptibly distorted.

    A few examples: Based on various bench tests I have dug up on the internet it appears that Ampeg SVTs commonly make about 270W at 5% THD and Orange AD200B commonly make about 165W at 5% THD. Keep in mind SVTs are are considered 300W amps and AD200Bs are considered 200W amps. Both amps will make more than their rated power but only if pushed into noticeable OD. Generally a good solid state amp rated for 300W will actually make at least 300W, and it will be very clean.

    Regarding the usefulness of a tube amp pushed heavily into OD. At some point the amp will continue to make more power, but it won't technically drive the speakers louder. When the amp is making clean power the output will resemble a sine wave. While the output resembles a sine wave, increased power is achieved by increasing the voltage. Increased voltage generates more SPL from the speaker.

    When the amp is pushed into clipping, the way it makes more power changes. No more voltage is available so the waveform starts squaring off. The increase in power is partly because the average time the voltage remains at its max value increases, and partly because the density of the harmonics increases.

    If the amp is pushed really hard it will cause the power supply to sag, meaning the peak voltage will actually decrease as the power approaches the maximum value. So you can push the amp to the point where an increase in power actually results in a decrease in SPL generated by the speaker.

    Also when you push an amp into OD, energy is transferred from the fundamental into harmonics. This is why the low end washes out if you push an amp too hard into distortion. Although it's a bit difficult to comprehend, the squared off wave you see on the output of a tube amp is not actually DC, its a result of the generation of lot's of harmonics.

    For the record, I own 28 amps that range in power from 12.5W to 2,500W. 20 are all tube, 4 are hybrids, and 4 are solid state. One of my solid state amps sounds almost identical to one of my tube amps, and many of my tube amps sound drastically different from one another. Rather than worrying about generalizations about tube VS solid state, just try a bunch of amps and buy the one that sounds best to you.

    I have a GK 700RB that is rated at 380W at 4 ohms. Below is a bench test video that shows an SVT making 340W at 11% THD (see 10:06 in the video), and 240W at 6%THD (see 10:40 in the video). I own two vintage SVTs and my 700RB is slightly louder clean than the SVTs pushed into distortion, so in my experience watts are watts. Basically my 380W amp is slightly louder than my 300W amps.
  20. kesslari

    kesslari Groovin' with the Fusion Cats Staff Member Gold Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones

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