Let's talk about amp power
Discussion
So I was wondering if someone could help me understand about amp power etc.
So originally I had always (maybe foolishly) assumed that a 100w amp had twice the out put of a 50w.
After reading about this is would seem to suggest that this is correct in terms of acoustic power, an amp with twice the watch would create 3db more than the other amp with half the wattage therefore doubling the acoustic power.
Reading on it suggests that because hearing is based on sound pressure you actually need 6db of volume to create double the sound pressure? Therefore if you wanted an amp twice as loud as your 50w you would need a 200w
Now on reading other bits and bobs it suggests that to create twice the volume you need 10x the wattage... So to get an amp twice as loud as your 50w you would need a 500w amp...
I normally use a little 5w amp and was thinking about getting a 12w number but if it's only going to have 20% or so power then I'll re think.
If someone could help me understand I would be very appreciative!
So originally I had always (maybe foolishly) assumed that a 100w amp had twice the out put of a 50w.
After reading about this is would seem to suggest that this is correct in terms of acoustic power, an amp with twice the watch would create 3db more than the other amp with half the wattage therefore doubling the acoustic power.
Reading on it suggests that because hearing is based on sound pressure you actually need 6db of volume to create double the sound pressure? Therefore if you wanted an amp twice as loud as your 50w you would need a 200w
Now on reading other bits and bobs it suggests that to create twice the volume you need 10x the wattage... So to get an amp twice as loud as your 50w you would need a 500w amp...
I normally use a little 5w amp and was thinking about getting a 12w number but if it's only going to have 20% or so power then I'll re think.
If someone could help me understand I would be very appreciative!
dojo said:
Now on reading other bits and bobs it suggests that to create twice the subjective room volume you need 10x the wattage... So to get an amp twice as loud as your 50w you would need a 500w amp...
This. And it explains why so many people who buy a 5W amp to crank-right-up at home find they need attenuators/VVR/PowerScaling. And why even a 1W amp is enough to stop Her Indoors enjoying EastEnders in the next room.One of the loudest amps I had (of the 30 or 40-odd I've had over the years) was a little 15w valve amp of obscure origin. It was waaayyy more noisy than the (nominal) 50w modelling amp that I used for gigging. My oppo in the band had a 30w Cornford which could overwhelm the 200w PA system that we had...
All numbers are open to interpretation in the music world, it would seem.
All numbers are open to interpretation in the music world, it would seem.
Bullett said:
What you are playing also makes a difference and how it's delivered. My mates AC30 would blow away Marshall stacks no problem.
Agreed, AC30s are incredibly loud. My Dad has an ancient one from the 60s and it blows away his 80w Marshall Valvestate combo. Sounds fantastic too.
In part it will be down to the speakers. I took out the Rocket 50 Celestion that was supplied in my Laney Cup and swapped it for a V30. The rated sensitivity is 98dB vs 95dB, and the difference in volume is huge.
Similarly I've used my 1987x, which is nominally 50W, through a borrowed 4x12 that was built for the Valvestate range (1924 cab?) and was able to crank it much harder than with my own 1960A or even 1936 (2x12) cabs. It's had a PPI master volume mod to make it usable in a pub venue.
Finally, remember that for a lot of non master volume valve amps the power rating is clean output, and true output with power distortion will be much higher.
Similarly I've used my 1987x, which is nominally 50W, through a borrowed 4x12 that was built for the Valvestate range (1924 cab?) and was able to crank it much harder than with my own 1960A or even 1936 (2x12) cabs. It's had a PPI master volume mod to make it usable in a pub venue.
Finally, remember that for a lot of non master volume valve amps the power rating is clean output, and true output with power distortion will be much higher.
Yes - I have been reading a lot about speakers and it seems that your bang on the money about that.
Maybe thats why an AC30 delivers so much power - It's not restricted by its speakers, plus I think they have a lot of clean headroom and that cut through a lot more than an amp thats breaking up.
In theory an AC30 will only have twice output sound as a 5w amp (headroom is key though maybe?) but the 2x12's will give a lot more spread than a 1x8 and a bigger sound?!?
From what I understand its a 10db volume increase to give double the "subjective room sound" so thats 10x the wattage (speakers being equal).
Does make me wonder why I carted stacks and twins round for years!!
Maybe thats why an AC30 delivers so much power - It's not restricted by its speakers, plus I think they have a lot of clean headroom and that cut through a lot more than an amp thats breaking up.
In theory an AC30 will only have twice output sound as a 5w amp (headroom is key though maybe?) but the 2x12's will give a lot more spread than a 1x8 and a bigger sound?!?
From what I understand its a 10db volume increase to give double the "subjective room sound" so thats 10x the wattage (speakers being equal).
Does make me wonder why I carted stacks and twins round for years!!
For starters a decent 4x12 (1960A or similar) produces a much better spread of sound at the same volume. A combo or even a 2x12 is much more directional and focused as a beam of sound. I doubt I'll ever gig the 2x12 but it's a lot easier to lug upstairs for rehearsal use.
Plus stacks just look much cooler
Plus stacks just look much cooler
When I was younger I always wanted to play through a full Marshall stack. I once played a gig where the provided backline was a set of them, and they were completely pointless. I was very glad to get back to my little Fender Hot Rod Deluxe, which has been used for everything from my bedroom (by me) up to a 20,000 capacity arena (by someone who isn't me!).
In a pub environment I couldn't push the amp at all - I might as well have DI'd into the PA it was so clean. At least with something smaller you can make it sing a bit.
In a pub environment I couldn't push the amp at all - I might as well have DI'd into the PA it was so clean. At least with something smaller you can make it sing a bit.
Depends on the stack. I used to use a DSL100, which is a modern master volume design. The lead 2 channel has all the dirt you could want, but does sound a bit sterile at times.
My 1987x was great from the off, but far too loud even with the volume on 1 as it's chucking out 50W plus at that point but with little gain. The loudness controls are just preamp gain, the power stage is on full all the time. It's now modified with a master volume circuit after the phase inverter, similar to a JCM 800 master volume, and it sings along at pretty much any volume.
My 1987x was great from the off, but far too loud even with the volume on 1 as it's chucking out 50W plus at that point but with little gain. The loudness controls are just preamp gain, the power stage is on full all the time. It's now modified with a master volume circuit after the phase inverter, similar to a JCM 800 master volume, and it sings along at pretty much any volume.
I honestly can't be bothered to lug my 2x12 Mesa about let alone my JCM800, much rather a little 5w matchless these days and mic it up, it pumps out enough for stage sound and anything else is up front.
My bro has a little 22w sessionette and that is loud (as is his AC30) both are very clean and you have to do everything via the board which is fine.
My bro has a little 22w sessionette and that is loud (as is his AC30) both are very clean and you have to do everything via the board which is fine.
dojo said:
JCM800
Here's mine, 1982 or 83, I can't quite remember. It's been modified before I owned it with an additional preamp valve and an effects loop.
It's utterly pointless me owning it as I'm not in a band at the moment. It's too loud to use in a rehearsal room, never mind at home
I still won't part with it though
I bought a Blackstar HT Stage 60 a year or so ago, in hindsight a 40w or even a 20w would have been plenty. It is louder than I will ever need, especially considering for bigger concerts you just hook it up to the PA.
I tell myself the twin speaker setup gives a better sound and I will have more clean headroom should I need it
I tell myself the twin speaker setup gives a better sound and I will have more clean headroom should I need it
HarryFlatters said:
Here's mine, 1982 or 83, I can't quite remember. It's been modified before I owned it with an additional preamp valve and an effects loop.
It's utterly pointless me owning it as I'm not in a band at the moment. It's too loud to use in a rehearsal room, never mind at home
I still won't part with it though
Very nice. It's utterly pointless me owning it as I'm not in a band at the moment. It's too loud to use in a rehearsal room, never mind at home
I still won't part with it though
I have a late 80s 50w version, but although I never gig it these days (due to it being far too loud) I can't part with it either. Obviously, as you know, even at low volume settings, it's got enough grunt to make ornaments waltz along shelves.
My gigging amp these days is a 2x12 JCM900 50w combo. I got excited when I was asked to perform at the BIC in Bournemouth, thinking that I'd be able to crank it a bit. I set it to 3 and the sound guys asked me to turn it down.
SWoll said:
What are you're thoughts on using an attenuator to manage the volume but still drive the amp at the sweet spot?
Not cheap, but wouldn't something like this make the JCM useable in rehearsals/at home even through a 4x12?
Those things, and the Marshall Powerbrake too, are both discontinued. They generate a _lot_ of heat too as the power has to go somewhere if you don't turn it into noise. Not cheap, but wouldn't something like this make the JCM useable in rehearsals/at home even through a 4x12?
As per my previous post, a PPI master volume is much cheaper and just works. Think it was about £25 in parts. Basically it adjusts the bias of the power tubes, making them run colder than intended and therefore lowering the output voltage.
This way with the extra pot turned down to about 1.5 I can use my 1987x at home. In rehearsals with a 2x12 I run it on about 5, with the bright channel on 4 and the normal channel on 9, which sits nicely with a DW drumkit and two other half stacks. And when we get onto outdoor stages I can wind it up to 10 and it effectively drops out of the circuit leaving the amp as Marshall intended.
SWoll said:
What are you're thoughts on using an attenuator to manage the volume but still drive the amp at the sweet spot?
I thought about buying one, but I'd rather pay Dennis Marshall to fit a master volume to my amp.I really must get it serviced soon, so I'll ask him about it. I'm not sure if it's even possible, but Dennis is the man who can tell me
Tom_C76 said:
As per my previous post, a PPI master volume is much cheaper and just works. Think it was about £25 in parts. Basically it adjusts the bias of the power tubes, making them run colder than intended and therefore lowering the output voltage.
Not true. It's simply a volume pot (most often a dual pot with a couple of capacitors) placed between the phase inverter valve an the power valves. It does not affect the bias in any way whatsoever.With a PPIMV you do not get as much power valve compression/distortion when turning down. At low levels you may get none at all. So if that's a significant part of your amplifier's cranked tone, it will be missing when you dial the PPIMV down to home-use levels. Examples here are AC30, Tweed Deluxe, Marshall 18W, etc - for those amps, an attenuator is the appropriate and easiest option. (With PowerScaling/VVR being sutable but more intrusive.)
Wattage rarely seems a good indicator of actual volume. I gigged for years with a Peavey Bandit 112 - classic first gigging amp. Had to crank it almost to 11 to be heard over the drummer and sometimes still couldn't be heard (fecking drummers). It was 85 watt.
Now I use a Blackstar id 60 tvp which is 60 watts and I'm yet to need to take it past 6, which is actually too much for most venues. The 'tvp' stands for ' true valve power' so it is supposed to be as loud as the equivalent valve amp. I'm not sure it is but its close.
Which begs another question - why are valve amps so much louder than solid state?
Now I use a Blackstar id 60 tvp which is 60 watts and I'm yet to need to take it past 6, which is actually too much for most venues. The 'tvp' stands for ' true valve power' so it is supposed to be as loud as the equivalent valve amp. I'm not sure it is but its close.
Which begs another question - why are valve amps so much louder than solid state?
Gassing Station | Music | Top of Page | What's New | My Stuff