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Is a watt a watt? Tube vs solid state


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  • Is a watt a watt? Tube vs solid state

    For all the guys using modelers with PA speakers, how many watts do you need to keep up with a rock band?

    It seems like a tube watt is lot more than a solid state watt. When Atomic first came out with cabs for the POD they had an 1825 watt tube amp and speaker. Now they come out with a 500 watt solid state amp and speaker.

    Prior to the CLR

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  • #2
    In my own totally unscientific experience tube watts are greater then solid state watts. I'd go with at least a two to one ratio.
    Cause sometimes the rhetoric don't go with the contents


    • #3

      A watt is a watt. The main differences between a tube and solid state amp are in what happens when they go into clipping. Also, it's a matter of how you're measuring things... and companies are known to use all sorts of different measuring tricks to make things look better "on paper" - you really have to be careful when comparing the specs between two different products, because as often as not, the reference points for the measurements don't always line up. Then there's the issue of speaker efficiency too. If you're measuring things the same way, and we're talking about both amps working within their design parameters (and not being driven into clipping), and both amps are driving identical loads, with the exact same speaker efficiency, then there's no difference between 1W coming out of a tube amp or a solid state amp.


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      - George Carlin

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      - Sir George Martin, All You Need Is Ears

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      • Player99
        Player99 commented
        Editing a comment

        I alway thought that the watt is actually a measure of heat, not decebels so if you have a very efficient 30 watt amp vs a very inefficient 30 watt amp the efficient amp could be much louder because it is not generating as much heat. Probably not the best way to put it but that is what I thought. I have a 35 watt tube amp that is very clean and loud. Much louder than it should be for 35 watts. Very expensive design and components.


    • #4
      Watt ratings for audio are measured at the speaker output. So in other words it doesnt matter whatsoever how efficient your amp is at using power. It matters how much power comes out of it. It's not a heat rating...

      Anyway Phil is right but theres a bit of a catch. What he said about breakup is absolutely right and very often people cannot run their ss


      • #5
        Beaten by seconds


        • Cirrus
          Cirrus commented
          Editing a comment

          Don't be sad! Be cat sad! :catsad:


          Good points about compression, Peak and RMS.

      • #6

        Also volume doesent increase liniarly with wattage. A 100 watt amp isnt twice as loud as a 50 watt amp, a 200 watt amp isnt twice as loud as a 100 watt and so on.


        • Phil O'Keefe
          Phil O'Keefe commented
          Editing a comment

          iwillfightu wrote:

          Also volume doesent increase liniarly with wattage. A 100 watt amp isnt twice as loud as a 50 watt amp, a 200 watt amp isnt twice as loud as a 100 watt and so on.


          Very true - and the range of volume levels that the human ear can detect is so vast, that the numbers are unwieldy to use... so instead, we use a logarithmic scale so we don't have to write down all those zeros. 50dB is not half as loud as 100dB - it's significantly less. And 50W is not half as loud as 100W - it takes a lot more power (and wattage is a measurement of power) to "double the volume."

          While individuals vary somewhat, in general, a doubling of perceived volume occurs with a 10dB increase in level. A 1dB increase or decrease is (in theory) the smallest most people can hear, although time and again I've seen people detect a 1/10th dB change in the studio. A 3dB increase is a doubling of power - but again, not a doubling of perceived volume levels. Not even close. A 100W Marshall will be noticably louder than a 50W Marshall, but definitely not twice as loud. And as Cirrus pointed out, we're talking about OUTPUT power here. How efficient the amp is (IOW, how much input power it uses to generate that output) doesn't really matter in the scope of this discussion.

          Where efficiency comes into play is at the speaker. Remember what I said in my first post about speaker efficiency? This is the single most often overlooked part of the equation. Speaker efficiency can make all the difference in the world when it comes to volume levels. A speaker is a transducer - it converts one form of energy (electrical) into another (acoustical). How efficiently it does so matters - a lot. In fact, most moving coil speakers (like what you have in your guitar amp) are terribly inefficient. Most of that 30W of power gets converted into heat by that speaker instead of acoustical energy. It's usually 80% or more that winds up as heat instead of sound. Create a speaker that approaches 100% efficiency, and you could play the largest concert venue in town with a Princeton and have no problem with people hearing you.

          All of what Cirrus said about how tube and solid state amps function was right on the money, and it definitely makes a difference in how loud the two get, and how we perceive them. In addition to that, If you're comparing a 30W tube amp with a highly efficient speaker (like an E/V EVM-12, which has a 103dB / 1W @ 1m rating) to a 30W solid state amp with a cheap, inefficient speaker (let's say 93dB @ 1W / 1m), the tube amp is going to sound much louder due to just the speaker difference. In fact, using those two speakers, you could run a 100W amp with the inefficient speaker, and a 50W amp with the EV, and they should measure about the same "volume" on a decibel meter! So when comparing a tube and solid state amp of the same "wattage", you need to make sure you're measuring things right (use the o-scope, make sure the SS amp is maxed out but just short of clipping, etc.) and you need to use the same speakers. 



      • #7
        If you are plugging straight into a PA, then you should be able to keep up by leveling your signal through the mixer. If you can't, then your bandmates are overpowering the PA, and you probably can't hear the vocals. So they should turn down.

        If you are looking for a rule of thumb for powering yourself outside of the PA, I've done just fine with 18 and 20 watt tube amps - they get plenty loud. Solid state, you'll want something commensurate with the wattage of your PA so that you can level in appropriately. Unless you're playing huge rooms , outdoors, or just like to blow out the doors with loud volume, I'd think a 500-700 watt solid state should be enough.

        Without getting into the science of why they are different, yes, wattage as a reference point for tube amps vs solid states don't line up.


        • #8

          i remember way back when we would take our amps to the lake and when you tilt the cab down by the water you could see the dent it made.  with the waves coming off and everything.


          you can't do that with ss amps...well you can, but they don't dent the same


          " "


          • eti313
            eti313 commented
            Editing a comment


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        • #9
          i disregarded your post and instead took the advice given by your name. it didn't work. give me better advice in the form of a name change