Is one Watt, 1 Watt, knowmatter what?

SunDevil

2 amps with all other parts of the signal chain identical and the same single ECC83 pre, no EQ into a long tail PI

1) A cathode biased pair of 6l6gts master volume maxed and rated to 30w
2) A cathode bias quad of El34s non
MV rated to 30w

Which is louder or do they produce the same output both as measured and as experienced by the human lug hole?

SunDevil

It's too early in the morning - I mean el84s of course! X_X

ToneControl

AFAIK once they are turned up beyond the "clean" level, you will get different waveforms, with different amounts of current away from "zero" (i.e. the area you can colour in between the oscilloscope trace and the zero centre line will not be the same. This then has further variables to consider with how the output impedance reacts with the speaker driver

 

Phil_aka_Pip

depends on the OT, the speaker, the cabinet, and the listener's  ears

richardhomer

The efficiency of the speaker will make a difference and the overall 'voicing' too. Some relatively low out-put amps sound 'big' (Matchless are a good example of this).

FWIW, I don't think you can really judge whether an amp will be 'loud enough' from its quoted output.

57Deluxe

What is a K-nowmatter?

SunDevil

Thanks all

By 'same signal chain' I'm assuming same guitar, lead, impedance out from the amp and same cab and speaker

Phil mentioned that the OT would have an impact - we all know that doubling the wattage gives you approx 3db and whilst I'm not conversant with the black art of transformer winding, surely a builder would go out if business pretty quickly if there '30w' amp was putting out sufficient unstated output to make a significant difference to volume and wold this start to blow speakers, that you or I would reasonably assume to be up to the job before then?

What am I missing?

TinLip

what?

ICBM

There can be quite a difference between measured rated output power and perceived volume. The best example is solid-state vs valve - you can have two amps which are genuinely exactly the same measured power output, defined as the maximum continuous clean power (to specified amount of total harmonic distortion, usually 1%)… but the valve one will sound a lot louder in use. There are real physics reasons and psycho-acoustic ones, but it's not true that there are "valve watts" and "solid state watts" - they are the same watts, but produce different results.

It's the same to a lesser extent with different types of valve amp. Cathode-bias vs fixed-bias, negative feedback, power supply design, EQ, where the first clipping occurs… all change the perceived dynamic volume even for an exactly constant measured output power.

It's also context-dependent - an amp with a big open bassy tone may sound louder in isolation or in a power-trio context, but one with a compressed upper-mid focused tone may well sound louder in a dense mix because it cuts through better, where the 'bigger-sounding' amp can get buried even though it's actually producing more sound energy.

Short answer - pieces of string vary in length. Try one and see what fits .

HAL9000

As ICBM has said, a Watt is a Watt no matter if the amp is solid state or valve. Also, a Watt is a measure of power, not volume. 

 The output power of an amp is measured at the point that the amp begins to distort. However, beyond this point valves and transistors perform quite differently from each other. 

As the power is increased valves will gradually become more distorted but it's the kind of distortion us guitarists like and expect. So if the amp is rated at 30W that is the point at which the amp starts to 'clip'. It is still possible to keep turning the volume up a long way beyond this point and still get usable sounds. So our amp (rated at 30W remember) might well be pushing out 50W or even more. 

Once a solid state amp is pushed past the point at which it starts to 'clip', everything happens much more suddenly. So, again for an amp rated at 30W, once it starts to distort it's not possible to turn it up much further before the sound is an unpleasant unusable mush. So this amp, again rated at 30W, may only be putting out a few extra Watts above its rated value.

Another thing to bear in mind is that most solid state amps are seen as budget/practice amps and simply do not have the same quality of components (such as speakers) or build that valve amps typically have.

Phil_aka_Pip

SunDevil said:

Thanks all

By 'same signal chain' I'm assuming same guitar, lead, impedance out from the amp and same cab and speaker

Phil mentioned that the OT would have an impact - we all know that doubling the wattage gives you approx 3db and whilst I'm not conversant with the black art of transformer winding, surely a builder would go out if business pretty quickly if there '30w' amp was putting out sufficient unstated output to make a significant difference to volume and wold this start to blow speakers, that you or I would reasonably assume to be up to the job before then?

What am I missing?

OTs vary in efficiency (power transfer) and different designs can affect frequency response, giving a perceived difference in volume.

paisleysoul

A Watt is a Watt no matter Watt!!

...anyone?

Headphones

paisleysoul said:

A Watt is a Watt no matter Watt!!

...anyone?

Absolutely, it's the law!

Oh My God...

I suggest the they're ultimately talking about is a mixture of SPL and a bit of human perception.