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WHAT is amp wattage and WHAT determines it. ik that the higher the wattage the later amp breakup occurs. which is why vox amps get overdriven so easily while marshall amps maintain a pretty clean character at louder volumes. whats got me confused is that the fender vibro kind is 60 watts while the twin reverb is 85, so i was looking into the vibro king's specs and the pre amp stage is 5 12AX7 groove tubes (12 * 5 = 60), so i thought the power stage wasnt part of the equation (or the reverb tubes for that matter). but then on the twin reverb, you have 4 12AX7 and 2 12AT7, which rounds up to 72. and now i dont know where the ground is anymore so if anyone would like to clue me in id really appreciate it

the preamp tubes don't add to the wattage, just count the power tubes, like 6550 / 6l6 / el34 / or el84 - all of which produce different wattage.

6l6 & el34's produce about 25w each, so four of them in a 100w amp, two of them in a 50w amp. 6l6's can produce 30w, so that's why you see a 60w amp or a 120w amp.

6550's are like 30-35w or whatever.

el84's are about 15w or something.


all of this is variable based on other factors of the amp, so for example a 6l6 doesn't ALWAYS produce 30w, but if you're trying to sell amp you wouldn't say that your amp is 'SOMETIMES 120W'.

i thought the prefix stood for the wattage also how so "sometimes" 120W. how does a tube's wattage vary? and then what does the prefix stand for? like, voltage drop?

fetusrobot wrote:i thought the prefix stood for the wattage also how so "sometimes" 120W. how does a tube's wattage vary? and then what does the prefix stand for? like, voltage drop?

The way the amps power section is designed determines the voltage as well as the power tubes used. Sloan is right about the wattages you can get from the tubes. Add into that equation whether the amps operating in class A or Class A/B that can determine the max or min wattage from said tube type. basically four 6L6 tubes can be 85watts or 100 watts. What do you mean by "prefix"?

i mean the first numbers in the tube's name like 6L6 (6) or 12AX7 (12). i thought a 6L6 would give a resulting wattage of 6W. plus doesnt wattage depent on Voltage and Amperage? isnt that the way it's calculated?

I suggest you spend some time doing google searches.

yeah i have and you can see how far that has got me. i thought it would be more productive to just ask the questions instead of depending on someones article

fetusrobot wrote:marshall amps maintain a pretty clean character at louder volumes

On the contrary, while 100w Marshalls are certainly loud they're also famously known to be instant crunch machines, such that they used to make a 200w model called The Major in the '70s just so you could actually get some cleans in a live performance situation (though Mick Ronson got his good and crunchy on a regular basis). The old non-master volume 100-watt heads that made "the marshall sound" famous in the '60s and '70s begin to distort at like 1.5 - 2 on the preamp volume.
JCM 800s had decent headroom but they definitely don't maintain their cleans further up the dial. Some post-'90s hybrid and multi-channel Marshalls can get loud and clean but that's because they were designed that way to compete with the modern amp market; it's definitely not something you think of when you hear "Marshall".

wtf seriously? that's not the case with dinosaur jr. tho? like i think it was maybe the super bass 100W that he kept the volume at about 4 or so? and he was playing with a boost and it was only on the verge of breakup? and how is it that with such high wattage the amps can get overdriven so easily?

its all about the gain stages you build into the amp. It could overdrive at 1 or 10 depending how the gain is cascaded and how much you drive each preamp tube.

so wattage has no definitive play on breakup point? how do i tell apart the amplifiers that breakup easily and the ones that stay clean?

fetusrobot wrote:wtf seriously? that's not the case with dinosaur jr. tho? like i think it was maybe the super bass 100W that he kept the volume at about 4 or so?

You can clean up with the guitar's volume knob with those old crunchy tube amps when they're edged into overdrive, as well as just play softer for less crunch, but 4 isn't super high-gain or anything on a plexi (Hendrix had everything on 10), it just definitely isn't clean. It's really hard to get loud cleans out of those, it's a really narrow setting between "clean, but sounds horrible" and "ah, there's my gig tone, distorting already".

Mascis uses a couple of stacks even in the small bar gigs so he can afford to set those heads cleaner and still be louder than god. He uses a lot of fuzzes too, so he probably does set his base tone slightly cleaner than the average Marshall SuperBear, but it won't be real clean and real loud at the same time, like a Twin.

i mean he sounded REALLY clean in Bulbs Of Passion norwegian wood 2008.
so what do i make out of this? does that mean wattage isn't a defining factor in breakup? how do i know which amps are gonna breakup sooner and which are gonna breakup later.

fetusrobot wrote:so wattage has no definitive play on breakup point? how do i tell apart the amplifiers that breakup easily and the ones that stay clean?

wattage of the power section determines the amps 'headroom' - but only for the power section. you can still slam the preamp section (12ax7's typically) and get distortion.

so why would you want a 100w amp if you are a metal bro?
the extra headroom is often attributed to a tighter and clearer sound. also more bass (100w is NOTHING when it comes to pushing bass frequencies at high volume)

why would you want a low watt amp?
you will achieve POWER TUBE breakup easier than the more powerful amps. some people prefer this sound over driving the preamp.


remember that power almost nothing to do with VOLUME in guitar amps. a 50w is generally only 3dB quieter than 100w and that's almost not a noticeable difference.

what exactly is headroom though. is it like, a wider limit before the audio signal gets clipped? and what's the difference between preamp and power tubes?

fetusrobot wrote:what exactly is headroom though. is it like, a wider limit before the audio signal gets clipped? and what's the difference between preamp and power tubes?

yeah, headroom is like the 'clean zone' before the signal starts to distort.

a signal from a guitar pickup or microphone is super duper low, so a preamplifier takes that signal and amplifies it before it hits the power amplifer which has enough power to move a speaker and recreate the original signal but much louder.

guitar > preamp > power amp > speaker

with that said, the preamp has more of an effect on the sound of the signal because....

a power amp is generally designed just to take a signal and amplify it without changing the character of the signal - that's the goal in an engineering sense; but when you hit the power amp hard, it will distort and some folks prefer that sound rather than the sound of the preamp distorting.

so if the preamp stage amplification exceeds the power amp's headroom, you get one kind of distortion, and when the initial signal exceeds the preamp tubes' capacity you get another? like with a boost?

fetusrobot wrote:so if the preamp stage amplification exceeds the power amp's headroom, you get one kind of distortion, and when the initial signal exceeds the preamp tubes' capacity you get another? like with a boost?

The preamp will never exceed the power amps headroom, thats not how it works. The preamp shapes the sound from your guitar(tone, gain stages, etc) and that goes to the power amp section where its made LOUDER. The power amp section only starts to distort when its REALLY REALLY loud because its can only amplify so much before going into power section distortion.
Does this help any?

Try this link:
http://www.marshallforum.com/workbench/ ... t-1-a.html

i see. so how does one overdrive the preamp tubes? (also thanks for the link i'll skim through it later )

You were right with the boost. It'll overdrive the preamp tubes - look at what an LPB-1 or an SHO do with the pedal volume dimed. That's preamp distortion (and sometimes clipping from the pedal itself as well) Also, if you're running a master volume amp with the gain high and the master low, (I believe) you are overdriving the preamp tubes for the distortion, not the power tubes.