Tube Watts vs. Solid State Watts

Among the top 20 mistakes of new guitarists, Guitar Player magazine lists “not knowing the difference between tube watts and solid state watts.”

Well, it’s been years since I’ve played, and a slew more years than that since I’ve played through a tube amp. So watts the difference?

“Tube watts” have a reputation for being louder than the equivalent “solid state watts”. Part of the reason is probably that most tube amps tend to be older, when folks used to measure the power outputs a bit more uniformly. Newer solid state amps sometimes fudge a bit on the specs, and if you read the specs carefully you find the wattage specified also involves a very particular test set up which is not at all typical for how you would actually use the amp.

Another part of it is due to the fact that tubes don’t clip as harshly when they are overdriven. The particular distortion you get from overdriving a tube is more pleasing to the ear for most folks, leading to the idea that you can push a tube amp more than you can push the same power solid state amp and still have it sound good. A 100 watt tube amp will sound “better” when it’s pushing close to 100 watts than a 100 solid state amp that is also pushing 100 watts. The tube amp therefore has more “usable” power than the solid state amp of the same rating.

I’m curious as to how much of this is audiophile folklore. Don’t most amplifiers have a lot of negative feedback? If that’s the case the amplifier output is relatively independent of the characteristics of the amplifier. Can you actually tell which is which if you don’t know which sound you are hearing?

I did find this. However there is no justification as to why the tube should be different other than the claim that the tube is more linear than the transistor. I have trouble seeing how this makes a difference even it true. Non linearity just means that the amplifier gain without feedback is different at different input levels. However the feedback corrects for this.

One possibility occurs to me. The author speaks of the difference between a solid state amplifier with lots of feedback as compared with a tube amplifier with little feedback. He also spoke of varying the amount of feedback and noticing a difference in the amplitude of the higher frequency harmonics. That’s not at all surprising. You can’t just change the amount of feedback willy-nilly without also changing the compensating networks. If you do just change the amount of feedback you are probably going to cause the closed loop response to rise at the high frequency end. This could account for the difference in the way a high feedback amplifier treats the harmonics as compared to a low feedback amplifier in the tests.

Valve amps tend to produce more pleasing harmonics than transistor amps, there are lots of theories about why this should be, some diametrically opposed .

Some think its because valve amps produce more odd harmonics and that those produced are more closely related to the fundamental frequency, and that solid state amps tend to produce a wider range of harmonics, some of which are less related to the fundamental and this can make them sound harsh.

There is no doubt that a valve amp sounds ‘nicer’ but when you start analysing the output, the solid state amp wins in terms of signal to noise, dynamic range, but somehow the solid state amp loses out on purely subjective assessment.

To stick to guitar amps, clipping a tranny amp sounds terrible, clipping a valve amp doesn’t, anyone can hear that.

Not guitar amps, I think the ‘presence’ control on old Marshalls actually worked by reducing the -ve feedback (waits to be shot down by an amp tech’). I’d think that using a lot of -ve feedback in a valve amp would defeat the object of using valves in the first place, when you push the amp too hard it would just clip like a tranny amp.

Playing a guitar through a hard-driven valve amp actually feels different from a tranny amp, so based on the sound, not sure there are some clever emulators about. But based on feel, absolutely.

As to the OP. I think the problem is that often the sound you want for rock guitar is that of an overdriven amp output stage. If you’ve got a valve amp of the right power you get that for nothing (just turn up to 11). If you have a tranny output stage you need to synthesise an overdriven signal (maybe using valves, maybe not) then amplify it cleanly - which needs more absolute power.

Wait, you’re telling us that if we replace the speakers in a tube and solid-state amp with resistors so there’s no sound whatsoever, you can tell the difference? I don’t think so.

I loved this part in casdave’s second link:

It’s refreshing to see someone cut through all the mumbo-jumbo and “voodoo thinking” with some nice reliable scientific principles! :stuck_out_tongue:

He just means they give a different response. There seems to be more compression with an overdriven tube amp which results in a smoother sound and you get a different emotive feeling from playing through one.

It should be noted that there is little difference between a clean tube amp and a clean solid state amp, the difference comes about when the output stages are overdriven.

I know it all sounds very subjective but the difference is real. Basically I can turn my 60W tube amp up to 12 and it sounds good (and increadibly loud.) If I turned my old 55W solid state amp up too much it sounded like crap and not very loud. They are both Fender amps.

There is a lot of mumbo jumbo about. But most of it concerns why overdriven tube amps sound better. The fact that they do sound different is pretty obvious to people who have played through both.

i’ve got to say, I read these posts with a certain amount of wonder. It sounds as if the idea with a guitar amplifier is to drive the output stage into saturation and cut-off thereby inducing intentional distortion.

In that case why bother with negative feedback at all? The whole point of negative feedback is to linearize the amplifier thereby reducing distortion and to make the performance independent of the characteristics of the amplifier.

If the purpose is to get a distorted signal why not run the amplifier linear and add a shaping network? That way the distortion could be made adjustable and you could any desired effect at the twist of a knob. Sort of like an organ.

As to the technical aspects, there is a lot of arm waving involved.

Not always, but sometimes. IIRC, Eddie Van Halen’s characteristic sound came from a particular Marshall amplifier with a few cheap MXR bran effects boxes, and the amplifier played very loudly. I recall an interview in which Eddie said that he liked to be able to feel the hair on his arms move from the sound. How he has any hearing at all left is beyond me.

Even if you aren’t cranking the amp to eleven, there’s a distortion you get from tube amps that shows up even at lower volumes. A lot of people (myself included) like the way this ends up making the guitar sound. If you run music through an amp like this it sounds like crap, but for a guitar it sounds good.

Most of the guitar amps I’ve looked at haven’t used negative feedback.

There are effects boxes that do exactly this. There are also very complicated digital effects processing units that can simulate everything from the unique distortion of tube amps to the effects you get from old fashioned spring and plate reverb units, and even the peculiar echo effects you get from someplace like a concert hall (which is not a simple delay echo). Units that do this well are very pricey. The el-cheapo effects boxes you get at ye ol local music store just don’t cut it. An overdriven cheap tube amp has a “good” sound that is difficult to replicate without expensive equipment.

You betcha. If you really get into it though, you find that while the explanations you get from some folks is really wonky, there is something to the particular sound that they are describing.

Anyone playing a guitar and amp will adjust their playing style based on what is coming out of the speakers. A transistor amp played at the edge of clipping will give the “squashy, spitting sound at the start of each note” that is mentioned in casdave’s first link, and the guitarist will probably choose between softly strumming for a clean sound or picking hard for a fuzzed out tone. A tube amp goes into distortion much more gradually and allows for a broader range of picking styles. Instead of playing on one side or the other of distortion and staying away from the transition, you’re playing around in the range between a clean sound and full distortion.

Well, if people like it it’s hard to argue. Sort of a musical placebo effect.

Yeah, but that’s sound, not feel.

True but it’s a part of the jargon, probably because “feel” is the common fast response feedback to touch.

Many electric guitarists want the opposite of a good hifi amplifier. They want something that adds character and colour to the natural sound of their guitar but not so much that they lose the tonal characteristics of the instrument completely.

How else do I describe this? I thought it was obvious I meant the experience of playing through an amp turned up loud (difficult to do without speakers) Death Ray explained it well. What I meant about the sound was that listening to someone else playing I couldn’t swear that the sound was produced by a valve amp (though it is a pretty distinctive sound) it could be other processing. It’s the response of the amp to the dynamics of playing the strings that makes it feel different.

i’ve ginally gotten the drift. The amplifier isn’t there to reproduce the sounds of the guitar. The guitar and the amplifier are one system and taken together they put out whatever the performer is after.

PS I forget to include speakers, weather, the acoustical impedance of the venue, and the listeners’ ears in the system. Each speaker has a different response to the various musical wave shapes. That response depends upon the speaker, the temperature and humidity and the acoustical impedance into which the speaker is working.

And besides, if you crank up the volume you can overload the listeners’ ears and they all will hear different things.