The Wattage Conundrum - My Take

[Deleted member 5962]

Ah ok. It definitely comes on fast in Modern. At home, master at 9:00 is getting pretty loud, as you know. However, I've had amps that were extremely "touchy" and literally jumped from not quite loud enough, to way to loud with a 1/16 inch movement on the master. When you said "uncontrollable" that's what it reminded me of. The Mini Rec comes on fast in Modern, for sure, but it is smooth enough that it can be controlled. There isn't that crazy jump in volume that some amps have. (My old Peavey Classic 30 was really bad about this!)

I've seen other guys complain about similar things with other Mesa amps, and sometimes it surprises me that people don't understand that when you have 3 modes on one channel, there must be SOME compromise when choosing a volume pot taper. Heck, they even put dual pots on some models (Mark V25) to combat this, but when you want multiple voices on one channel, there's only so much you can do. Plus, as you well know, Modern mode is sort of a beast. LOL

Of course, a lot of this boils down to how loud you practice/play at home/ etc. And some amps just don't sound that great when turned down.

 

[Kred]

I'm thinking about this like an amp builder. Low power (tube) amps typically compromise the output transformer and power supply to save cost. They are targeting bedroom volume players, so the transformers are smaller and lighter weight, thus inefficient especially at lower frequencies. At standard tuning, a low E string is 82 Hz for guitar and 41 Hz for bass (31 Hz for 5 or 6 string bass). Low frequency cutoff is an important output transformer efficiency spec, for good bass response you want a cutoff much lower than your lowest string frequency. Looking at one catalog, an 80 Hz cutoff transformer weighs X and costs Y. The same transformer with a 40 Hz cutoff weighs 2X and costs 2Y, and with a 20 Hz cutoff weighs 3X and costs 3Y (they're pretty much priced by the pound).

The power supply has the same cost-efficiency tradeoffs. If you build in the extra energy capacity to handle the music dynamics, you've spent about as much as a higher wattage amp. Your low wattage amp will sound great and have volume near its higher wattage cousins, but no one wants to pay for it. The extra cost buys you efficiency of power transfer.

 

[László]

I'm thinking about this like an amp builder. Low power (tube) amps typically compromise the output transformer and power supply to save cost. They are targeting bedroom volume players, so the transformers are smaller and lighter weight, thus inefficient especially at lower frequencies. At standard tuning, a low E string is 82 Hz for guitar and 41 Hz for bass (31 Hz for 5 or 6 string bass). Low frequency cutoff is an important output transformer efficiency spec, for good bass response you want a cutoff much lower than your lowest string frequency. Looking at one catalog, an 80 Hz cutoff transformer weighs X and costs Y. The same transformer with a 40 Hz cutoff weighs 2X and costs 2Y, and with a 20 Hz cutoff weighs 3X and costs 3Y (they're pretty much priced by the pound).

The power supply has the same cost-efficiency tradeoffs. If you build in the extra energy capacity to handle the music dynamics, you've spent about as much as a higher wattage amp. Your low wattage amp will sound great and have volume near its higher wattage cousins, but no one wants to pay for it. The extra cost buys you efficiency of power transfer.

Interesting post!

I've said for a long time that I like the "big iron" in an amp, that it makes a difference, and is one reason I like the bigger amps. You've just explained why.

 

[Deleted member 5962]

I know what you mean, Les, and agree in many cases. Don't forget though, about the amps that are designed with small transformers on perpose as part of their design, and it works to make them better at some things than a bigger transformer would. If you've ever heard a classic and great sounding Fender Champ, that's what I'm talking about. I have a buddy that had one for years and that little thing sounded GREAT!!! I mean, just turn it almost all the way up, and it sounded like SRV tone. A few years back the OT finally went out on it. He decided to replace it with a bigger one... you know... more headroom, more bottom, etc. It took him about 20 seconds after he got it back, to realize it didn't SOUND as good. It had more headroom and more solid bottom, but the tone was not as good. He kept it about a year, before having it replaced with a new smaller one. I've heard a very similar thing when I toyed with power supply caps in my old Valve Jr.

 

[pac90]

Ah ok. It definitely comes on fast in Modern. At home, master at 9:00 is getting pretty loud, as you know. However, I've had amps that were extremely "touchy" and literally jumped from not quite loud enough, to way to loud with a 1/16 inch movement on the master. When you said "uncontrollable" that's what it reminded me of. The Mini Rec comes on fast in Modern, for sure, but it is smooth enough that it can be controlled. There isn't that crazy jump in volume that some amps have. (My old Peavey Classic 30 was really bad about this!)

I've seen other guys complain about similar things with other Mesa amps, and sometimes it surprises me that people don't understand that when you have 3 modes on one channel, there must be SOME compromise when choosing a volume pot taper. Heck, they even put dual pots on some models (Mark V25) to combat this, but when you want multiple voices on one channel, there's only so much you can do. Plus, as you well know, Modern mode is sort of a beast. LOL

Of course, a lot of this boils down to how loud you practice/play at home/ etc. And some amps just don't sound that great when turned down.

I've learned a lot from this thread, and I'm in the home player only demographic, but how loud is room loud, I mean I have 3 levels starting at kids sleeping to being able to hear it outside the house. Next time I'm home I'm going to use a decibel meter app on my phone to see what they are.

I got the idea from this guys video, where he's demoing pedals at 'room volume' of 82decibels

Which is kind of my way of saying that some pedals are good for non clean tones at 'family volumes', for want of a better term

(I only have a few years till my son reaches teenage years and bursts all 'family volume limits' and ear drums, all this gear is free to him grab. Heh Heh.)

 

[Deleted member 5962]

I hear ya. For YEARS I wasn't allowed (yes, I said that. LOL) to play very loud at home when my wife and daughter were there, because I had a child and my wife didn't think there was any real reason to do so. Of all things, she was at Guitar Center with me one day, and the guy I deal with there was talking about tube amps, and he said "well if you can't turn it up loud enough to make the tubes work, there's no sense in even having a good amp." And my wife looked at him and said "what???" like she couldn't believe it. I reminded her that I'd been telling her for years, that my nice, but lower powered tube amps needed to be a bit louder than she liked, before they really started sounding good. And she said "yeah, but I always thought that was just an excuse to turn it up loud like you do your music in the car." He and I had a laugh, but I swear, from that day since, she tolerates me turning it up MUCH louder at home. Now, she doesn't even say anything unless I start drowning out the TV (3 rooms away) and if I do that, sometimes she just goes out to the other TV room which is all the way at the other end of the house.

Anyway, for years, I had to use pedals to get decent tone at home because I couldn't turn my amps up loud enough to sound very good. So I know exactly what you mean.

Edit: Also worth noting as it backs that point, for years, I didn't chase great amps. I was a "clean amp plus pedals" guy and I flipped pedals all the time. As soon as she started letting me turn up some, I started buying amps specifically for their clean AND OD channels tones. (Side note: Amp flipping is MUCH more expensive than pedal flipping. HAHAHAHAHAHA)

 

[László]

I know what you mean, Les, and agree in many cases. Don't forget though, about the amps that are designed with small transformers on perpose as part of their design, and it works to make them better at some things than a bigger transformer would. If you've ever heard a classic and great sounding Fender Champ, that's what I'm talking about.

I have played through many a vintage Fender Champ, going back to amps owned by friends and bandmates in the 60s (I started in bands around 1965), and one of my closest buddies has what most would consider a nice '65 to this day. Lots of session players have brought them into my studio.

But I'll be hated for saying this -- I've never liked 'em.

I think they sound like what they were intended to be - practice amps, beginner's amps. Something for a player to warm up on before a show in the green room, or for a 13 year old kid to wank on.

I know. I'm weird. And yes, Clapton, Layla, I know, all that. Great song. Even a good recorded tone.

But Champs have never been my thing. I really mean it when I say I like bigger amps. I've never had one under 30 watts I could keep for more than a couple of weeks. Same with AC15s, Subway Rockets, Marshall 18s, many others. Had 'em all in my studio, some I've owned. Not my thing.

 

[Kred]

DreamTheatreRules has a point. Early Champs sound great because they have that musical kind of distortion (even-order harmonics) instead of the harsher clipping type of distortion (odd-order harmonics). I think for 3 reasons - a single 6V6GT power tube has 8-12% distortion at rated output power, compared to 2% distortion for a 6L6GC pair at rated output power. The 6V6 is not that linear, and produces nice-sounding even-order harmonics by slightly overdriving it. The second reason is the output transformer was often a higher primary impedance than the tube spec which lightly loads the tube letting its output swing more freely into the non-linear region. Third the power supply's 5Y3GT rectifier tube is really weak and has the most voltage sag of almost any rectifier tube (much more than a GZ34 or 6CA4). The combination of a soft output tube, soft output transformer, and soft power supply allowed sweet saturation without harsh clipping.

 

[László]

DreamTheatreRules has a point. Early Champs sound great because they have that musical kind of distortion (even-order harmonics) instead of the harsher clipping type of distortion (odd-order harmonics)

As I understand it after many years of studio geekery, distortion happens as tubes begin to clip and the signal begins to proceed from sine to square wave. Odd-order harmonics do come a little bit from tubes, but mostly it's even-order, while transistors tend to clip mainly in odd-order harmonics.

In fact, in a tube amp - any tube amp - there is a progressive, gradual flattening of the sine wave as the signal distorts, and any such flattening is clipping. I addition, the top of the sine wave is compressed, and more harmonics are generated. This is true of any tube that is overdriven.

"Clipping" as I understand it, is simply another word for the top of the sine wave going to square wave, and it happens as soon as the tube begins to distort. Because the top of the sine wave flattens and is thus said to be "clipped."

As I understand it further, there aren't two types of clipping with tubes. There is one type, that progressively gets more and more flattened as gain is increased, and as the sine wave becomes more square.

I could be wrong. I'm in fact, happy to be shown where I'm wrong, but I'm going to need a better and more comprehensive explanation.

I'm no scientist, but I do occasionally lecture at U of Michigan's Music School about music production, and at AES meetings, and I always like to learn new things that I can pass on in my talks.

Fortunately, we do happen to have a rocket scientist here on the Forum who might be able to provide further enlightenment, as he has studied the characteristics of tube amps. Aristotle, where are ya buddy?

 

[Kred]

If you look at a tube transfer function, it is not a straight line. This non-linearity (distortion) contributes the nice-sounding, even-order harmonics and happens before hard clipping is reached (the harsh-sounding, odd-order harmonics). Once over-driven to its hard limits, the odd-order distortion dominates by chopping the tops off the waveform. I think of this as two types of tube distortion - the transfer function non-linearity before clipping, and the hard limiting known as clipping.

Transistors are more linear than tubes, their transfer function is a straight line. This is why transistor total harmonic distortion (THD) is extremely low compared to tubes. There is practically no even-order harmonics at normal signal levels. But when the signal hits the power supply rails, it chops the tops off the waveform turning sine waves into square waves. This clipping contributes the harsh-sounding, odd-order distortion that transistor amps are known for. Hope this helps.

 

[László]

If you look at a tube transfer function, it is not a straight line. This non-linearity (distortion) contributes the nice-sounding, even-order harmonics and happens before hard clipping is reached (the harsh-sounding, odd-order harmonics)..

Actually, I've read that distortion in tubes is in fact highly gradual and progressive, and something like this graph of a tube distorting. And all of my 50 years experience playing tube amps of every type seems to confirm this. You can see a very smooth line, and the clipping distortion increases very smoothly on about a one to one basis with output level:

This is as opposed to solid state, which hard clips with odd order harmonics on the peak on the far right of this graph:

The transistor you might think of as hard clipping, and the tube isn't doing that. I'm not ready to buy your explanation.

So please explain to me why you believe that the Champ somehow behaves differently than other tube amps when it clips?

 

[rugerpc]

 

[László]

Kred may in fact know more about this stuff than I do. I'm not teasing when I say I'd like a better explanation.

There must be something one of us is missing here, and given my non-engineering background, it's most likely me that's missing something.

But when I've looked at graphs showing tube transfer functions, they look smooth, progressively distort in direct relation to output levels, and I never seem to see a sudden jump like we see on the extreme right of the solid state graph.

This also corresponds to what my ears tell me, that tubes distort in an extremely smooth and progressive way, and that solid state amps either have to model this behavior in software, or in other circuitry, but in any case, they don't naturally function the way tubes do.

I could have posted other charts showing sine waves of tubes progressively flattening as the gain increases, something else solid state circuits don't naturally do, but in any case, they all seem to point in the same direction as what I've described,

I've never personally seen anything showing that 6v6 tubes behave in any significantly different way as gain increases than EL84, 6L6, EL34, KT77, or other larger tubes, but I won't assume that data doesn't exist simply because I haven't seen it. I'm sure, however, that each tube has its own characteristics, but what I'm talking about is the progressive distortion that smoothly increases with gain.

Always trying to be open minded here.

OK, wait. Usually trying to be open minded here.

 

[László]

You know, here's what I find most interesting about tubes, and I'll start by describing the behaviors of some acoustic instruments, though all acoustic instruments do this to a greater or lesser degree:

If you bang on a piano really hard, it will generate additional harmonics. Play it softly. and a big reason it sounds different is that you hear fewer harmonics. If you blow a saxophone hard, you will generate different harmonics than if you blow softly, too. Over-blow a flute, and the harmonics actually predominate over the fundamental tone, it shifts an octave up! Strum an acoustic guitar really hard, and the top generates overtones that the guitar doesn't generate when you strum gently.

Incidentally, this ability to generate overtones acoustically is one thing that piezo transducers whiff on, they can't reproduce it. One reason I don't like them.

So when you plug an electric guitar into a tube amp, and play it softly, you hear one thing, but if you crank the guitar, and set the amp just right, when you hit the guitar hard, the amp will generate additional seoncd-order harmonics via tube distortion, in a smooth and gradual way -- just like an acoustic instrument does.

I think this is why so many of us love tube amps. Because they, in a combined system with an electric guitar (or for that matter an organ or electric piano) behave like great acoustic instruments.

Our ears like that. I'd even go one step further and say that our ears crave that aspect of music making.

You know what I hated about playing the accordion as a kid? Besides that it looked goofy as HELL? Damn thing could only generate so much harmonic content. The bellows could only blow the reeds inside the box so hard. They sound too smooth, there's no emotional oomph. No wonder strolling musicians in cafes in Paris played them. They're quiet, tame, little beasties. No "zetz". You can't play rock and roll on one of the damned things unless you're doing an impression of Freddie and the Dreamers. When I went back to piano and started rocking out on one, man, I could generate so many more colors! Organ, too. Crank that organ up, use a volume pedal, and man...you can make it quiet, like "Whiter Shade of Pale," or you can scream a solo like "House of the Rising Sun."

I never liked playing nylon guitar for the same reason. Too tame (for me).

But an electric guitar with a tube amp? There's your emotional bang for the buck, in spades.

People tell me I'm a tube snob, I don't like modelers, blah blah blah. But look, I'm no hi-fi snob. I'm into getting that last milligram of emotion out of my playing -- heck, with my lack of skills, I'll take whatever I can get. If you look at the graphs I posted above, you can see exactly why I feel the way I do about real tubes.

 

[aristotle]

Haven't had a chance to read through this in detail, but I think you guys are saying the same thing. Kred's explanation is right, but I think you're saying the same thing Les. If you think of a simple sinusoid going into a tube amplifier stage, it's always somewhat distorting the waveform. When the sinusoid is near it's minimum, to say around 20 percent of maximum, let's say that the output / input is...say....3 to 1 as an example. Then as the sinusoid starts going toward its maximum, the input / output relationship might be more like 2 to 1. So, the output doesn't look exactly like a sinusoid any more. The peak part is squished a little in comparison with the parts closer to zero. Still though, the output is a very smooth waveform. It's just been "distorted" in shape relative to the input waveform.

A solid state amplifier is much more capable of accurately maintaining the input / output relationship of a waveform so long as the waveform doesn't get bigger than its power supply. Sinusoid in, sinusoid out. No squished top. Since we have grown accustomed to squished tops in our music, the super accurate nature of a solid state amp seems "sterile", and not "warm". That's mainly because we just like the squished sound that comes out of a tube amp.

Kred's explanation of even versus odd order harmonics is correct, but it might be easier for you to think about it as more like sharp corners (which turn out mathematically to generate odd harmonics in its frequency domain representation.) On a tube amp, if the input waveform is big enough (because Les decided to dime his DG30) so that the tube is trying to generate an output signal that is beyond what it is capable of (based on its power supply and its gain and other factors), then it just outputs as much as it can for the portion of time that the input waveform is too big....which with Les' dimed DG30, is probably about 70 percent or more of the waveform. The thing of it is though, a tube isn't really good at generating sharp corners in the output waveform. Yeah, it'll cut off the top of the waveform, but it isn't efficient enough to go from a highly positive slope to straight flat. Because it's been gradually reducing the amplification that it's generating as the waveform increases, by the time the output gets to the rail, the slope of the waveform is going down towards zero anyway.

A solid state amp will also cut the top off of waveforms, but it's better at it. A sinusoid through a transistor can result in an output waveform that has a highly positive slope for the portion of the waveform that it can keep up, and then it will just "wham", lop that sucker totally flat. It's the sharp corners (or odd harmonics) that many people like us don't find pleasant.

Of course we don't generate sinusoids from our guitars, and the way an amp responds to the musical nature of a guitar output for example is what defines how an amp "feels" to us as we play through it.

As far as something like a champ goes, that's a different discussion.

 

[László]

Haven't had a chance to read through this in detail, but I think you guys are saying the same thing. Kred's explanation is right, but I think you're saying the same thing Les. If you think of a simple sinusoid going into a tube amplifier stage, it's always somewhat distorting the waveform. When the sinusoid is near it's minimum, to say around 20 percent of maximum, let's say that the output / input is...say....3 to 1 as an example. Then as the sinusoid starts going toward its maximum, the input / output relationship might be more like 2 to 1. So, the output doesn't look exactly like a sinusoid any more. The peak part is squished a little in comparison with the parts closer to zero. Still though, the output is a very smooth waveform. It's just been "distorted" in shape relative to the input waveform.

A solid state amplifier is much more capable of accurately maintaining the input / output relationship of a waveform so long as the waveform doesn't get bigger than its power supply. Sinusoid in, sinusoid out. No squished top. Since we have grown accustomed to squished tops in our music, the super accurate nature of a solid state amp seems "sterile", and not "warm". That's mainly because we just like the squished sound that comes out of a tube amp.

Kred's explanation of even versus odd order harmonics is correct, but it might be easier for you to think about it as more like sharp corners (which turn out mathematically to generate odd harmonics in its frequency domain representation.) On a tube amp, if the input waveform is big enough (because Les decided to dime his DG30) so that the tube is trying to generate an output signal that is beyond what it is capable of (based on its power supply and its gain and other factors), then it just outputs as much as it can for the portion of time that the input waveform is too big....which with Les' dimed DG30, is probably about 70 percent or more of the waveform. The thing of it is though, a tube isn't really good at generating sharp corners in the output waveform. Yeah, it'll cut off the top of the waveform, but it isn't efficient enough to go from a highly positive slope to straight flat. Because it's been gradually reducing the amplification that it's generating as the waveform increases, by the time the output gets to the rail, the slope of the waveform is going down towards zero anyway.

A solid state amp will also cut the top off of waveforms, but it's better at it. A sinusoid through a transistor can result in an output waveform that has a highly positive slope for the portion of the waveform that it can keep up, and then it will just "wham", lop that sucker totally flat. It's the sharp corners (or odd harmonics) that many people like us don't find pleasant.

Of course we don't generate sinusoids from our guitars, and the way an amp responds to the musical nature of a guitar output for example is what defines how an amp "feels" to us as we play through it.

As far as something like a champ goes, that's a different discussion.

Thanks, Aristotle! This helps me understand it.

 

[Deleted member 5962]

Actually, other than the word "sinusoid," that's exactly what I was going to say!

I'm only partially kidding. And I didn't get into it as far as what Kred was taking about. I was using the Champ and my Valve Jr's I toyed with, as examples of amps whose power sections (be it the OT or the power supply caps) significantly affected the tone and how changing them changed the amp.

But this is a rabbit hole that can get way bigger. I was just saying that it's not JUST the tubes that run out of gas in "some" designs, and that some amps (not just small ones) are designed to have power sections that run out of gas a bit to provide a certain feel to the amp. But after generalities like that, it gets way more complicated quickly because as I also mentioned, its a sum of ALL the parts of the amp that determines how it sounds and feels.

I used to hang out in the Valve Jr. mod forums. I did one test where you basically only doubled the amount of power supply caps. I did one with a bigger OT and no increase in power supply caps. Then both. All of these affected the headroom, punch, squish, feel, bottom end, etc. of the amp. Modifying such a simple circuit lets you learn first hand just how much these things matter and more importantly, just what they do. But I'm just a hack, so...

 

[László]

Well, the technical issues aside, I suppose one doesn't have to justify whether one prefers big amps, or low powered amps. We all have our different preferences. I've never been out to "prove" that my own taste is somehow better. Everyone's is equally valid. But it's mainly valid for each person. We don't have to agree.

As I said many times, my preferences aren't prescriptions for other people to follow. They're merely topics for fun discussion.

I like what I like, and I've found that I like bigger amps with more power in reserve and so on.

Really, isn't that the point of any such exercise? Finding what you like, and using what you like to do what you enjoy doing is what being an electric guitar player is partly about.

Oh sure, there's the playing. But I think our choice of gear even affects how and what we play, and vice-versa. With my hands as screwed up as they are, I can't play for more than a few minutes without taking a break. So....I'm here a lot blabbing about what I like.

 

[pac90]

I can't remember if I suggested it before Les, but I had that planet waves varigrip a while back, and it may be good for giving your weak hand physio and rewiring the cranium to digits (I'm an engineer, not a doc)
It certainly did what it said on the can for a newbie with little left hand finger strength

 

[László]

I can't remember if I suggested it before Les, but I had that planet waves varigrip a while back, and it may be good for giving your weak hand physio and rewiring the cranium to digits (I'm an engineer, not a doc)
It certainly did what it said on the can for a newbie with little left hand finger strength

I've used a medium tension Gripmaster for years, but just saw that the Varigrip has variable tension, which might be a good thing for me! So I'll get one today if they're in stock locally.

I have two issues going - one is the numbness of the fingertips of the ring and pinky fingers. No grip exerciser can solve that one, and it does make things kind of tricky on the fretboard, and the other is weakness of the whole hand, but that seems to be the result of the left hand's nerves only receiving 1/3 of the nerve signals that my right hand's fingers are receiving (per the doc who gave me the EMG).

So when the brain tells the fingers to move, they aren't getting the signal at anywhere near full strength, and that's not only causing weakness, it's causing them to become uncoordinated. Barre chords have become nearly impossible, for example, and that's mainly about the lack of finger coordination and numbness. The fingers don't know where they are, and don't go where I tell them to go anyway. Throw in the weakness, and it's kind of a mess.

So I'm not playing very well - that's frustrating - but I AM playing and I'm not going to stop playing until I can no longer play single notes.