question about amps running 6L6GC tubes

[pompira]

tube amps put out more power when overdriven.

all wattage ratings are always measured at clean power.

so if i have the master volume at 10 but the preamp only at 3,
am i crossing the line?

[diagrammatiks]

it depends on the amp.

100 watts isn't really that loud clean.

If your master is on ten and you turn the preamp up until you hear distortion you are most likely pushing past whatever stated wattage the amp is.

[Firestorm]

Jana and I fight all the time! (Not really). Output power of an amp (with a given set of tubes) mostly depends on plate volts, plate current, plate load and AC volts of the signal driving the power amp. It's that last one that the amp manufacturer has no control over: how big is the signal coming from the guitar to begin with. The preamp has a maximum gain by design and might be set using a a specific input voltage. Use a different guitar and all bets are off. That's why I say to take the power rating with a grain of salt.

There are a lot of different "100W" Marshalls; with hot pickups, some of them can likely do 180W heavily distorted (most published ratings are power before clipping, tho). Other Marshalls run a much lower B+ and likely can't get close to 180W.

Technically, you should be able to get 100W from just a pair of EL34s (based on Mullard's data sheets), but I can't think of anyone who tried to do it commercially.

[Jana]

Firestorm,

I wasn't picking a fight with you (you would win) nor was I disagreeing. I was just saying that a 100 watt amp can put out a lot more than 100 watts if it is pushed hard. But, after 50 watts or so, it doesn't matter--deaf is deaf!

[Jana]

Addendum: What I posted does not contradict what Firestorm wrote. Amp makers typically post the power for a certain distortion level. They should, if they are honest, post the power at a low distortion. But, in order to boost the numbers, they may measure at 5 to 10% distortion, sometimes more.

[renshen1957]

No marketing department ever understated the output power of anything.

excellent! i mean, it's bad that they lie, but a little less power never hurt a speaker.

No marketing department ever understated the output power of anything. As a hypothetical, you can sue anyone for any cause. Whether you prevail is a different matter entirely.

i hear you.

thanks again

Hi,

In the 1950's Fender advertised their Tweed Bassman Amps 5F6-A as a 60 Watt amps.

That's an engineering accomplishment considering it was fueled by two 5881 Tubes.

However as far as I have experienced, speaker efficiency influences loudness, how many dBs SPL at one Watt between 95 dB at 1 Watt and 107

Best Regards,

Steve

PS Yes I know the about dBs and the relation to loudness.

[pompira]

[...] If your master is on ten and you turn the preamp up until you hear distortion you are most likely pushing past whatever stated wattage the amp is.

i'm not sure i feel so joyful about hearing that.

[...] There are a lot of different "100W" Marshalls; with hot pickups, some of them can likely do 180W heavily distorted (most published ratings are power before clipping, tho). Other Marshalls run a much lower B+ and likely can't get close to 180W. [...]

isn't B+ the same as plate voltage?

if NOT, please disregard what i'm about to post.

----------------

so a marshall meant to see 115V mains
connected to 120V mains will output more power
than a marshall meant to see 230V mains
connected to 220V mains? (the latter is actually my situation)

But, after 50 watts or so, it doesn't matter--deaf is deaf!

i know your post was addressed to firestorm, but i recommend earplugs (they're cheap)
to anyone playing a loud amp. not that i use them myself.

[...] What I posted does not contradict what Firestorm wrote. [...]

i see. it's not just black and white when talking about output power, is it?

[...] However as far as I have experienced, speaker efficiency influences loudness [...]

hell, removing the back from my cabinet influences loudness,
even if i don't touch any of the guitar/fx/amp settings.



-------------------

again, thanks so much everyone for their input.

[Structo]

Output transformers, speakers, input signal, distortion, etc. all affect output power.

Really all you need to know is that a 50 watt amp is loud.

And a 100w+ amp is damn loud!

[Firestorm]

so a marshall meant to see 115V mains
connected to 120V mains will output more power
than a marshall meant to see 230V mains
connected to 220V mains? (the latter is actually my situation)

This is technically true, but at levels measured in milliwatts. And only the power amp is affected; changing supply voltage to preamp stages doesn't affect gain, (except maybe an eensy-weensy bit).

[Reeltarded]

No marketing department ever understated the output power of anything.

excellent! i mean, it's bad that they lie, but a little less power never hurt a speaker.

No marketing department ever understated the output power of anything. As a hypothetical, you can sue anyone for any cause. Whether you prevail is a different matter entirely.

i hear you.

thanks again

What did you blow up?

[pompira]

What did you blow up?

nothing, gladly.
but i know i'd be upset if i did.

==============================

there's more stuff i wanna know.
may i ask it here?

[diagrammatiks]

[...] If your master is on ten and you turn the preamp up until you hear distortion you are most likely pushing past whatever stated wattage the amp is.

i'm not sure i feel so joyful about hearing that.

why? what are you afraid of blowing? Just make sure there's a little wiggle room in your speaker cabs.

There's a reason the historic Marshall is a 100watt amp with 2 quads of greenbacks. The first speakers were rated at 25 watts and a single 412 would blow.

[pompira]

why? what are you afraid of blowing? Just make sure there's a little wiggle room in your speaker cabs.

There's a reason the historic Marshall is a 100watt amp with 2 quads of greenbacks. The first speakers were rated at 25 watts and a single 412 would blow.

well, i wasn't afraid of blowing anything until certain facts came to light.

i'll give you the relevant info on the amp/cab i'm using.

the amp is labeled at 60W rms output even though it uses a pair of 25W tubes
and the cabinet is labeled at 100W rms output even though it uses a pair of 60W speakers.

==================

taken from my previous post:

there's more stuff i wanna know.
may i ask it here?

[Firestorm]

There's a reason the historic Marshall is a 100watt amp with 2 quads of greenbacks. The first speakers were rated at 25 watts and a single 412 would blow.

The side benefit of that is that doubling the output power of the amp only results in 3dB of increased "loudness," which is perceptible, but only just so. Doubling the surface area of the speakers gets you another 3dB increase (in SPL) on top of that, so you don't have to actually see people's ears bleeding to know you're too loud.

[pompira]

i've decided to be a bastard and ask more stuff anyway, even if it this might not be the most adequate place.

do you know when people talk about making readings with a multimeter,
they always say things like "measure between pin X and GROUND?

what if the amp isn't grounded?
what if it's an old amp with a two-prong mains cable?
or what if the amp has a three-prong mains cable but it's connected to an old socket without ground wiring?

does that mean the readings will be inaccurate?
does it mean the readings will be zero?
does it mean you'll fry your multimeter?