Question about cabs and valve amps

Discussion in 'Amps and Cabs [BG]' started by Nickthebassist, Jan 6, 2005.

  1. Ok, let's say I have an 800watt rated 8x10 cab. I put an 800 watt rated valve amp on it, what happens? Does the valve amp have too much volume and power for the cab?
  2. Brendan


    Jun 18, 2000
    Austin, TX
    If a cab is rated for 800 watts, you're generally safe putting in however damn much power you please. I wouldn't hesitate at all to put 2000 watts into an 800 watt 8x10.

    Mind you, the volume would never go above about 4, but it wouldn't make the cab explode your mother or anything.
  3. timv

    timv Supporting Member

    Jun 7, 2000
    Chandler, AZ
    I wouldn't recommend overpowering it much at all. I had an svt cab I bought brand new and had 1800 watts to it and blew one of the speakers after having it for only a few months. The local shop I worked with was a pain in the @#$ at trying to get it replaced under warranty. I wasn't playing it very loud and had no distortion. I think the preamp may of put too much bass out or something, it was an swr iod. I ran the same setup through my other 8x10 which was a nemesis cab and never had a problem. Traded the svt cab for a henry 8x8 and ended up selling the nemesis. Also, an 800 watt valve amp? Where are you getting that from? Must weigh about 300 pounds!!!
  4. It was just a hypothetical question.
  5. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    from a cabinet's standpoint, 800 watts is 800 watts valve or solid state. Valve amps sound louder than solid state amps of the same wattage for a few reasons, but not because they really have more watts.

    ps, i wanna see the price tag and weight of an 800 watt valve amp!!!
  6. Lyle Caldwell

    Lyle Caldwell

    Sep 7, 2004
    Well, a solid state rating is not determined the same way a tube rating is, by and large.

    Take a 30W solid state amp. That measurement means that at the onset of distortion, the amp is producing 30W (simplified here, but still accurate for our purposes). And since it's solid state, once it distorts, it sounds bad.

    Now take a 30W tube amp. Here's where it gets complicated. The 30W is measured at the point where the signal begins to be distorted (measured on a scope). But the distortion here typically sounds good. In fact, long after the scope says it's distorted, our ears still hear a clean sound. And if you keep on turning it up, yeah, we'll hear the distortion, but we'll like that sound.

    Futher complicating things is that few tube amps are measured at rated exactly the same way. Furthermore, the rating they are assigned depend on a certain kind of tube at a certain bias point.

    For example, a Marshall JTM45 is usually called a "50W" amp. But in reality it can range from 20 something watts to just over 40 watts, depending on what rating and kind of tubes are used, and how the amp is biased.

    Another example is the Fender Twin Reverb, which in its original black faced version produced 85W. But remember those 85W are measured at the point where the signal begins to breakup. The amp will actually go much louder before you hear the distortion.

    To make a solid state amp that will keep up with a JTM45 or Twin Reverb, you have to have "more wattage" on paper, even though the actual decibels produced by the speaker may be the same when measured consistently.

    I hope that makes sense.

    It's not that "tube watts are louder" but tube amps are measured at the onset of distortion even though they have a lot of musically useful volume range above that onset point, whereas solid state amps "hit the ceiling" musically when they reach the onset of distortion.

    Further complicating all this is that few people realize how loud a 30W amp is, and that a 100W amp isn't really that much louder (though most 100W amps are connected to more speakers than most 30W amps, so there's more speaker surface area, which can be more important than wattage). A 30W AC30 can easily keep up with an 85W Twin Reverb and a 200W SVT (the SVT needs more power to produce the low bass signals at a comparitive volume to the guitar amps).

    To sum up, don't look only at the wattage ratings on amps.
  7. Lyle Caldwell

    Lyle Caldwell

    Sep 7, 2004
    In combination with my above post, I want to reference Ivan Mike's comment that tube amps "sound louder." This is true, in many cases, because the distortion added by the tubes gives our brain "cues" that the sound is louder. Our brains associate distortion with Very Loud Sounds, so if you're listening to two amps at the same weighted volume at the same distance, you will hear the amp with slight distortion as the louder of the two.

    And by "distortion" I don't mean it sounds like Megadeth. Even slight compression, the presence of even ordered harmonics, and a bit of "growl" is heard as distortion, even if you would describe the sound as clean when asked.

    I suggest googling "fletcher munson" if this interests you.
  8. awesome explanation! cheers lyle!
  9. Just a question to add to the topic... if I have a 100 watt solid state head, I can match it with a 100 watt solid state cab and not have too much problem cranking up the volume right? But if I have a 100 watt tube amp, I imagine it's closer to 200-300 watts solid state, volume wise. How should matching it to a cab work? Would it handle the 100 tube watts simply because it's 100 watts, or does it work by volume and blow or something?