watts?

[Bmxbarspin724]

does anyone know how much watts a ampeg rocket 2 has? and does anyone know the rough conversion of tube watts to solid state? i know there is a difference, i was just wondering how much.

sorry if this isnt the right thread, im new here.

[Wakculloch]

Reckon from the circuit it should be 20 to 30 watts ie pub, club practice room level.
Watts is watts ennit.
Subjective loudness of valve amps seems (from personal experience, not dB measurements) seems to be from a bit more to a lot more. I play through a 20 watter, and if i needed to get equivalent SS volume i'd want a 50 (for a cleanish sound).
Reasons for this phenomenon are said to be;
(Complete and enlighten me)

[teemuk]

Watts are watts. Loudness, on the other hand, pretty much depends on speaker system’s efficiency.

[Enzo]

People confuse power and power ratings a lot. If you produce 20 watts from a solid state amp into an 8 ohm speaker, and also 20 watts from a tube amp into an identical speaker, all things equal they will be about as loud as each other. A 20 watt solid state amp will not be as loud as a 20 watt tube amp as a rule. AS you turn the tube amp up, it compresses, while the SS amp just clips.

SO ther is a distinction between a 20 watt amp and an amp putting out 20 watts.

That may be overly simplistic, but it is the general idea.

[Steve Conner]

The reason why "tube watts" are louder is that the tube amp sounds great when it's overdriven, so you can use that part of the dynamic range.

You're actually abusing the amp into putting out more than its rated power, and like Enzo mentioned, at the same time it's compressing and clipping your pick attacks out in a musical way, which increases the average level of the signal and makes it louder still. Meanwhile the poor damping factor of the tube amp is letting the speaker resonate and punch out more bass and presence.

Solid-state amps don't naturally do any of these things. An overdriven solid-state power amp just sounds nasty, in a way that makes you want to turn it down. Unlike tube overdrive that makes you want to turn it up more.

So all solid-state amps have to run the power amp clean and get the compression in a tube simulating preamp. Before amp makers realised this, solid-state gear sounded awful. Pick attacks were like treading on a floor covered in Rice Krispies. Now, with good preamps and current-feedback power amps that lower the damping factor, solid-state watts are probably getting bigger.

You have to set all this off against the fact that tube watts weigh about three times as much as solid-state ones, and cost 5-10 times as much to buy.

[teemuk]

What is tube compression if not clipping, and not all tube clipping is soft and heavenly. On that remark, not all solid-state clipping is hard and ugly either. How an amplifier behaves when it’s pushed beyond its average output power limit is a very case-specific issue and the outcome (tone-wise) is highly subjective. Not all people appreciate clipping (no matter how soft it is) and even if we speak about that, circuits have evolved a lot and nowadays we have plenty of solid-state amplifiers that can do soft clipping decently in both preamplifier and power amplifier.

If you can live with smeared (and at the extreme severily clipped) tone then yes, some tube amplifiers may seem more powerful than equally rated SS amplifiers. On the other hand, some may not and some may seem even less powerful. The point is: You never know, as the whole issue of difference in tube and SS watts has been ridiculous from the beginning. Tube watts being seemingly more powerful is perhaps a general rule but it never should have been and we should stop spreading it as one. Heck, one can even find similar differences by doing side-to-side comparisons with tube and tube, or SS and SS amps! In reality, there are far too many factors that define this "output power" at certain settings of a system to be discussed here.

The reason I mentioned speaker efficiency is that it has a much greater effect to overall loudness than the output power. A watt by itself does nothing. A system always needs a transducer - a speaker - that converts the amplifier’s output power to sound waves. The efficiency of this transducer is critical since it's one of the weakest links in the audio chain. If we consider the typical “one tube watts equals about two SS watts” cliché the increase in SPL from doubling the power is only 3 dB. Not much, one could barely hear that. In fact, a typical speaker may have bigger notches and bumps in its response throughout the bandwidth. It would be considered extremely HiFi if it didn’t have. To double the loudness using the amplifier itself the output power should be increased as much as by tenfold. This begins to show how absurd the watt comparisons actually are. On the other hand, the 10 dB increase required for that [doubling of loudness] is much more plausible just by doing a carefully thought speaker swap.

[Wakculloch]

There is also the phenomenon of class A amps sounding louder than AB/B.

None of this really matters except as a gigging musician, I know how much volume i roughly need for a venue size etc, and wattage is the stated quantity on almost all amps, so that is the yardstick i use.

Another thing which may go some way to explain these effects is the tiddly power transformers on transistor class B amps. In this mode you can get away with under specifying this component, and hope that it never makes it out of the bedroom.

[Steve Conner]

Teemuk, that's true, except remember we're discussing musical instrument amps. One man's "smeared and severely clipped tone" is another man's "All Along The Watchtower". We don't just live with it, we love it.

I can't stress enough that musical instrument amps never operate truly clean at gigging levels. Even a clean channel will be performing about 6, maybe 8, 10dB of peak clipping, in a subtle, musical way that you don't even notice.

I make no distinction between compression and clipping, because they both achieve the same thing: increase the RMS-to-peak ratio of the signal so a smaller power amp will sound louder. It's exactly the same as the speech processors folk used to use on CB radios. The cheap ones were just a diode clipper followed by a bandpass filter.

[kg]

also do not forget the effect on total system loudness of the higher output z typically seen from valve amps.

a watt is actually not a watt when you're talking about reactive loads.

[black_labb]

There is also the phenomenon of class A amps sounding louder than AB/B.

None of this really matters except as a gigging musician, I know how much volume i roughly need for a venue size etc, and wattage is the stated quantity on almost all amps, so that is the yardstick i use.

Another thing which may go some way to explain these effects is the tiddly power transformers on transistor class B amps. In this mode you can get away with under specifying this component, and hope that it never makes it out of the bedroom.

now theres the uestion about wether you are really talking about class A as the technical term, or what some builders call class a.

a real class a amp is almost always going to be a single ended design, at least for guitar amps.

[Wakculloch]

Unless your the awkward pedantic person that is me, who likes building multiple pair, push pull, class A amps that weigh a ton and put out low wattage.
The tranny amp load missmatch issue is another can o' worms.
Probly more of an issue here, where 16 ohm cabs are the norm.

[Enzo]

teemuk, I'd be right with you to agree that speaker efficiency has a marked effect on loudness in an amp, but it is aside from the original question. You can add or subtract decibels from an amp's output by changing the efficiency of the speaker, but it doesn't affect the difference between tube and solid state performance. Play the two type amps through a 94db efficient speaker and it won't be as loud as the same amps played through a 102db efficient speaker, true. But the differences in loudness comparing the two AMPS would remain - one would seem louder than the other played through any one speaker you select. And that was the point.


And there is clipping and then there is clipping. The solid state amp runs into a brick wall - the power rail - and the signal waveform stops right there right now. The result is in sharp edged flat top waveforms that sound awful. REmember we are talking watts and output, not preamp overdrive we can massage through several stages of tone shaping. The tube amp when pushed does not hit a brick wall, it just runs into the ends of the curves, so it rounds off the corners, resulting in a much smoother more mellow distortion.

I am sure we can always find an individual who prefers square waves or whatever, but the overall atttitude doesnt reflect that preference.

[Steve Conner]

I agree

About the 16 ohm standard, I never realised that was a UK thing. The first valve amp I owned only had a 16 ohm output, so I just always used 16 ohm speakers without thinking about it. Now I have another amp with a choice of 8 or 16, so I'm spoiled for choice

But I guess you could be onto something, all the Marshalls, Hiwatts, Selmers, Orange or whatever, had 16 ohms, but I can't think of any Fenders that did.

The square wave distortion thing is a good point. I remember experimenting with running an analog synth through various amps and stompboxes, to make distorted basslines for drum'n'bass. A mic'd tube amp just sounded too nice. I actually did end up overdriving a mixer channel to get that harsh square wave clipping.

[7591A]

I think watt you are talking about is distortion. Single ended, push-pull, solid state. Its a condition from when you are running clean to the distortion level. The smoothe sign wave output peaks become flattened or 'clipped'. Also tube amps produce what is known as odd harmonics that are more pleasant than even produced harmonics that are SS notoriety. Sustain is more pleasant in an over-driven tube amplifier for this reason. That is, the input signal is a bitt more than the output tube can handle before distorting or 'clipping' the signal. There is also cross-over distortion that is produce in anything other than class-A amplification. Although class-A requires larger output transformers to be able to handle the continuous current produced by the output tubes always 'on'. Larger transformer equates to larger cost, more money. Tube amps require larger hardware, more money. One reason is higher voltage for the voltage amplification and plates. Higher voltages bigger power transformer more money. On the other hand SS is a current amplifier. Lower voltages less money. Solid state power supplies cost less.

[loudthud]

When an amplifier is rated for output power, be it tube or solid state, a load resistor is used and a voltage reading is taken. If two amps, one tube and one solid state, produce the same voltage across the resistor, then they have an equal power rating. When you are talking about loudness however, you must be using a speaker. The simple fact of the matter is that a 50W tube amp will put more voltage across a speaker (when overdriven) (at most frequencies) than a 50W solid state amp. Warm up your scope and try it. Play a guitar through a tube amp into a load resistor and observe the clipping level. Now substitute a speaker and note the increase in clipping level.

The reason for this is the reactive behavior of speakers and the "saturation" behavior of the tube or transistor driving it.