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What's the maximum watts an amp can have?


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I know 100 and 120 watts is the standard. I also heard of 150 watt heads like the mesa triple rec. but what's the maximum no. of watts an amp can have and why is that the maximum? 

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There have been guitar amps made that exceed 100, 120, and even 150 watts - for example, the Marshall Major was a 200W amp. 

Why do you think there's a maximum? 

There really isn't a theoretical limit on amplifier wattage - just practical limits. No one really "needs" a 1,000W guitar amp, but it would be possible to build one. In fact, there are plenty of 1,000W amps on the market - but they're generally designed for purposes where that kind of power is needed and useful. Bass amps, PA systems, etc. 

Why do you think someone would need or want more than a hundred watts or so for a guitar amp? 

 

 

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Well first, there is no 'standard'...and in this day and age, why anyone thinks they need more than a 30W [tube/valve] stage amp is beyond me.

There is, of course the whole 'clean headroom' thing, but frankly, it is mythological when one considers the increase in actual volume between a 30W amp and a 100W amp is negligible.

Fender made a 400W amp way back when, which is arguably the highest wattage tube instrument amp ever built by a major manufacturers. Before that, the Ampeg SVT ruled the roost at 300W. Those are, of course, bass amps, not guitar amps...Phil mentioned the Marshall Major, which at 200W was top dog for a while but was plagued with issues, not the least was the HV power supply.

24 minutes ago, SteinbergerHack said:

The Kemper powered head is 600W.

That said, what difference does it make?  An amp's power output is only one small portion of the volume equation, and has nothing to do with the sound quality.

The Kemper Profile is 600W, but it is a class D amp, not tubes, so apples and oranges there. But I totally concur that volume does not dictate sound quality.

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8 hours ago, SteinbergerHack said:

The Kemper powered head is 600W.

That said, what difference does it make?  An amp's power output is only one small portion of the volume equation, and has nothing to do with the sound quality.

All true and a point I actually wrote an entire article about in an effort to dispel some of the myths about wattage and loudness.

 

 

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Posted (edited)
18 hours ago, Phil O'Keefe said:

There have been guitar amps made that exceed 100, 120, and even 150 watts - for example, the Marshall Major was a 200W amp. 

Why do you think there's a maximum? 

There really isn't a theoretical limit on amplifier wattage - just practical limits. No one really "needs" a 1,000W guitar amp, but it would be possible to build one. In fact, there are plenty of 1,000W amps on the market - but they're generally designed for purposes where that kind of power is needed and useful. Bass amps, PA systems, etc. 

Why do you think someone would need or want more than a hundred watts or so for a guitar amp? 

 

 

Ah I get it... the guitar and every other instrument has to compete with the loudness of the drums. so the loudest drummers are leveled with by 100 watts. anything more than that is not necessary. that sounds like a reasonable reason. I guess you can make an amp infinitely loud but there's no point anymore to go over 100 watts, right? 

and the 100 watt amp can be turned up to 4 before the power stage starts to distort. so a 100 watt amp it doesn't get any louder past 4. how many decibels would that be equivalent to?  

Edited by mbengs1
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2 hours ago, mbengs1 said:

Ah I get it... the guitar and every other instrument has to compete with the loudness of the drums. so the loudest drummers are leveled with by 100 watts. anything more than that is not necessary.

Well, sort of... from a practical standpoint you do want to be able to balance the sound of the various members of the band, but once you pass a certain size in terms of the venue, even the drums will require amplification - you can't play an arena without miking up the drums through the PA system. 

BTW, drummers aren't measured in "watts" - they're measured in the Sound Pressure Levels (SPL) they can generate - the same as the "loudness" of amplifiers are. 

Did you read the article I linked to? You should... it will give you a better understanding on how wattage, speaker efficiency and "loudness" work. 

And even with a hard-hitting drummer, not everyone needs a 100W amp. I have a 20W amp (with a highly-efficient Electro Voice 12" speaker in it) that can hang in there just fine with a rock drummer / five piece band... 

 

Quote

and the 100 watt amp can be turned up to 4 before the power stage starts to distort. so a 100 watt amp it doesn't get any louder past 4.

That entirely depends on the amp... as well as the speaker(s) it is connected to. While that may be generally true for SOME amps, it's not a universal truism at all. 

 

Quote

how many decibels would that be equivalent to?  

Again, I suggest you read the article I posted. There's simply NO WAY to determine how loud any amp is going to be simply on the basis of its wattage. As I point out in the article, there are some cases where a 50W amp can sound louder (IOW generate higher SPL) than a 100W amp....

https://www.harmonycentral.com/articles/guitar-and-bass-amps/wattage-speaker-efficiency-and-amplifier-loudness-r195/

 

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2 hours ago, mbengs1 said:

I guess you can make an amp infinitely loud but there's no point anymore to go over 100 watts, right? 

Actually no, you can't make an amp "infinitely loud."

While there is no real limit on wattage, there IS a limit on how loud things can actually get. It has to do with physics... sound can not travel in a vacuum - it has to travel in a medium (generally speaking for the sake of this discussion, that's air...) and it travels in pressure waves - where the air molecules are alternatively compressed and then rarified. Without getting too far into the weeds with you, the air on our planet generally can't support sound levels that are any higher than around 194 dB SPL at standard atmospheric pressure. Remember though, as I also point out in the article, the decibel scale is logarithmic, not linear - there's a HUGE difference between 50 dB SPL and 100 dB SPL, not just a "doubling" of volume. A "doubling" of perceived volume comes with a difference of around 10 dB SPL.

Also remember that with increasing SPL, safe exposure times drop, and drop dramatically. You don't want to be exposed to high SPL's for long periods of time - doing so can cause irreparable damage to your hearing!

I strongly suggest that all musicians and even music fans have a look at this page, and get a SPL meter (or SPL app for their smartphones) and use hearing protection whenever they're playing at loud levels, or are going to be exposed to any loud sounds - especially for prolonged periods.  

 

 

 

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Posted (edited)

The limitations are going to be based on the components that comprise the circuits and their power consumption.  Theory vs reality are two different things.  Tubes especially are limited to the components and tubes readily available. They aren't designing new audio tubes any more so you're stuck with what's available for building amps which is pairs of tubes which produce maybe 120W total.  I've seen 200W guitar amps and 300W bass amps but anything larger really isn't practical cost wise or in actual use.  You could spend a half a billion dollars designing and tooling a new factory to manufacturer a new type of tube and there is no guarantee it would sound any better then what's already available. You could spend tens of thousands making all the support components as well and build an amp nobody wants to buy too. 

 Whey spend all kinds of money designing a single 400W tube amp when you can simply buy 4 X 100W amps?   Its much cheaper to simply buy several smaller amps and a hell of a lot easier to move them too. 

Or you can do like most guitarists. Get one great sounding amp and simply mic it.   

There was a time when manufacturers were in competition building high wattage stage amps. I still have a Sunn Concert lead head from 1967 which is 200W.  I don't play many places where I can actually use i6t however.  I used it as a bass head driving mid speakers mostly.   The trend for big amp designs pretty much ended with the rise of much larger sound systems capable of micing an entire band.  When I was a kid something like a Vocal Master, Kustom, Vox etc PA was pretty common for most working bands. Most weren't much more then 100 to 200W tops and were only used for vocals.   Musicians could easily get by with 30W amps that matched the loudness of a drummer.  Even the Who during the 60's which were noted as being one of the loudest bands ever only used Vox or Marshall PA's which weren't more then 4X12 speaker columns with 200w heads.  They typically offered additional power amps to run more cabs.  They would use those PA's often without any instrument mics or stage monitors and simply used louder instrument amps for big shows.  

pa1.JPG.217c926e2fea957be4d4080f04b3d96d.JPG 

Late 60's early 70's you saw some of the really big systems being used at shows like Montgomery Pop and Woodstock.  

bp1.JPG.19edb35cab7d6a04b56e0dc3138051bd.JPG

 

By the mid 70's just about any band you saw playing a large venue had huge systems.  I saw at least two dozen shows at the Phili Spectrum PA's this size was pretty normal. 

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It wouldn't matter what size amp you use on stage.  If its miced people will hear it. if it isn't, they wont. 

Many metal bands and headliners still use some big stage amps but much of that is for show.  Since about 2000 the trend on amp size has been getting smaller.  Speakers are more efficient so you can use smaller cabs and be just as loud as the old ones.  Why pack a 4X12 marshal cab with 25W speakers and use 4 cabs when you can pack one cab with 4 X100W speakers and actually be much louder due to them being twice as efficient.  Hauling less gear means fewer roadies to move it and that means you get to keep more of the money you earn instead of paying hired help. 

There were musicians even back in the 70's who found some of the smaller tube amps could produce some really great tones. So long as they miced them up it was no problem.  If you need to play louder, simply bring more PA gear and mic the amp.  If you cant afford the gear hire a sound company to do all that work.  You can show up at a gig with everything you need in two hands.  

 You can take  all that energy you waste moving big amps and put it into the music instead which in turn gives the audience a better show.  Dogging huge amps at 3 in into a truck sucks big time.  Try it for a few years and you'll learn soon enough.   When you haul big amps you typically have to unload all that crap when you get home too so nobody breaks into the truck and steals it.  If you can put it all in the trunk, nobody's going to even know its there and you can always get it out in the morning. 

 

 

 

 

Edited by WRGKMC
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Need moar words. 

Amps are loud. When you put a mic on them and run them through a PA they're louder. If you need them louder you turn up the PA. 10,000,000,000 Watts is probably a decent working maximum, but use your ears. 

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Posted (edited)
On 3/12/2020 at 7:10 AM, mbengs1 said:

I know 100 and 120 watts is the standard. I also heard of 150 watt heads like the mesa triple rec. but what's the maximum no. of watts an amp can have and why is that the maximum? 

After having chuckled my way through reading this thread, I finally realized that there is a reasonably accurate answer to this question, and one that is based on the basics of physics, power amp design efficiencies and electrical distribution practices:

At 120VAC (North American power), the largest common circuit capacity is 20 Amps.  Thus, the theoretical maximum power that can come from a single 120VAC power outlet is 2,400 Watts.

For a Class A amp @ 50% efficiency, the maximum you could get from a single 120VAC outlet would be 1,200 Watts.

For a class B amp @ 75% efficiency, the maximum you could get would be 1,800 Watts.

For a class D amp @ 90% efficiency, you could get very close to 2,160 Watts.

 

Problem solved.  Do I get a cookie?

Edited by SteinbergerHack
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Posted (edited)

 

3 hours ago, SteinbergerHack said:

After having chuckled my way through reading this thread, I finally realized that there is a reasonably accurate answer to this question, and one that is based on the basics of physics, power amp design efficiencies and electrical distribution practices:

At 120VAC (North American power), the largest common circuit capacity is 20 Amps.  Thus, the theoretical maximum power that can come from a single 120VAC power outlet is 2,400 Watts.

For a Class A amp @ 50% efficiency, the maximum you could get from a single 120VAC outlet would be 1,200 Watts.

For a class B amp @ 75% efficiency, the maximum you could get would be 1,800 Watts.

For a class D amp @ 90% efficiency, you could get very close to 2,160 Watts.

 

Problem solved.  Do I get a cookie?

1800 watts for a class b amp? 20 times louder than a 100 watt? that's awesome! way too loud. for any situation. 

Edited by mbengs1
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1 hour ago, Grant Harding said:

1800 Watts is nowhere near 20 times as loud as 100 Watts. Close to twice as loud. 

just twice as loud for that much watts? cool...  

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12 hours ago, mbengs1 said:

just twice as loud for that much watts? cool...  

which is why it is just plain dumb to haul stacks around when a 15-20W combo amp will get the job done

Steinberg's numbers are 'theoretical'...no one is building amps anywhere near those values, and for a number of good reasons.

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On 3/12/2020 at 6:56 AM, daddymack said:

Fender made a 400W amp way back when, which is arguably the highest wattage tube instrument amp ever built by a major manufacturers.

I remember the 400 PS - those 435W heads were absolute monsters. They must have weighted in at over 80 pounds for just the head and used six 6550A tubes. One of Ed Jahn's crazier creations IMO... 

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20 hours ago, daddymack said:

which is why it is just plain dumb to haul stacks around when a 15-20W combo amp will get the job done

I've been saying that for years. My Princeton Reverb II's 20W RMS into its Fender / E/V 12F is plenty loud enough for my needs. 

Some guy has a NOS Fender (E/V) 12F up for sale on Ebay right now at an absolutely insane price... 

https://www.ebay.com/itm/ULTRA-RARE-NOS-NIB-Vintage-Fender-12F-Speaker-Electro-Voice-EV-EVM-12L-JBL-D120-/264341118433

 

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22 hours ago, daddymack said:

which is why it is just plain dumb to haul stacks around when a 15-20W combo amp will get the job done

True, though if you want really crisp clean sounds, you may well need more power.  What's counter-intuitive for beginners is that the "loud" and "heavy" high-gain guitar sounds are actually easier to get with a low-power amp than a high-power amp (while retaining proper cochlear geometry and limiting discussions with local law enforcement).

22 hours ago, daddymack said:

Steinberg's numbers are 'theoretical'...no one is building amps anywhere near those values, and for a number of good reasons.

Well, not just theoretical - that's the actual reality of what can be done with a single standard 120VAC power input.

I would also say that while there are no guitar amps being built at those power levels, there are plenty of PA amps at very high power ranges, and they are in fact limited by the available line power.  Here's a spec sheet that shows output ratings based on line Voltage and current:

https://jblpro.com/en/product_documents/ithd2_power_draw___thermal_dissipation-pdf-63302653-b757-4346-a3a4-8eced83863fd

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2 hours ago, Phil O'Keefe said:

I've been saying that for years. My Princeton Reverb II's 20W RMS into its Fender / E/V 12F is plenty loud enough for my needs.

As have I...I dumped my Marshall 100SL/1960A half stack in the early 80s and never looked back...and my back thanked me after every gig...

2 hours ago, Phil O'Keefe said:

Some guy has a NOS Fender (E/V) 12F up for sale on Ebay right now at an absolutely insane price... 

https://www.ebay.com/itm/ULTRA-RARE-NOS-NIB-Vintage-Fender-12F-Speaker-Electro-Voice-EV-EVM-12L-JBL-D120-/264341118433

Yeah that is a crazy price, but... somewhere there is some gearfreak who will buy it to hold onto...

I know I've seen used/reconed 12F speakers going in the $2-300 range, and yes they were a very expensive option.

A good friend/band mate had the JBLs in his SF Twin, and when he wanted to get a custom 2x12 extension cab made, he couldn't get the same JBL E120s, and the only option was the EV12s/Fender12F, he took a pass...

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6 minutes ago, SteinbergerHack said:

True, though if you want really crisp clean sounds, you may well need more power.  What's counter-intuitive for beginners is that the "loud" and "heavy" high-gain guitar sounds are actually easier to get with a low-power amp than a high-power amp (while retaining proper cochlear geometry and limiting discussions with local law enforcement).

Yes, if you want really crisp and clean, then you are far better off with a solid state amp rather than a tube amp...I think many beginners are 'betrayed' by their cheap SS practice amps, like the Peavey Bandit 75, which sound , well, we know how they sound cranked up, and so, beginners who do not understand the difference between a tube amp and a SS amp erroneously make the 'more power' leap to 100W...

7 minutes ago, SteinbergerHack said:

Well, not just theoretical - that's the actual reality of what can be done with a single standard 120VAC power input.

I would also say that while there are no guitar amps being built at those power levels, there are plenty of PA amps at very high power ranges, and they are in fact limited by the available line power.  Here's a spec sheet that shows output ratings based on line Voltage and current:

https://jblpro.com/en/product_documents/ithd2_power_draw___thermal_dissipation-pdf-63302653-b757-4346-a3a4-8eced83863fd

I said 'theoretical' because there are no tube instrument amps, or for that matter SS/digital instrument amps actually being made to those wattage specs, even though it is certainly possible to do so...but just because you can do something, does not mean you should do it...

The thermal issues are eventually going to be mitigated by new materials/processes that will either dissipate the heat generated more efficiently, or drastically lessen the heat generated...not today, though...

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