Thanks Bill, but your response answers the opposite of what I'm asking. I'm not trying to find out if tube enthusiasts like the sound of less clipping from more powerful amps. Rather, I'm asking if they prefer the sound from less powerful amps, and if so how to decide which power rating provides the best tube sound given an amp's characteristics together with the speaker sensitivity and the preferred listening level.
Maybe I need to explain how "tube sound" is partially related to distortion? I didn't want to do that here, and I'm not really the person to do it. An earlier post from Atmasphere explains the sound charateristics of push-pull circuitry. While that may be the most important influence on "tubiness", it's only part of the story. One also needs to consider harmonics that occur when an amp is almost or even softly clipping. These harmonics can be pleasing to the ear at certain levels.
Tube people, please feel free to add or subtract to my knowledge here. As stated I'm a tube audio newbie hence this post.
Anyone else want to take a stab at asking my question in an easier-to-understand way? Atmasphere? |
Hi-fi amplification is not the same as with guitars. You want want your amps to be running in their lowest-distortion range, every time (or as close to that as possible given your SPL needs) -- whether tubes or SS. And you can still clearly hear the effects of tube rolling even when amps are perfectly well within their "clean" range.
Too much power doesn't cause problems unless you're careless and let a very high-power signal through to your speakers -- besides that scenario, it's generally safer to have more power, to avoid clipping (which can be problematic for tweeters). When it comes to protecting your gear, there's no silver bullet -- some care and education will be required by yourself, whether you choose tubes or SS, high power or low power.
I run 250 Watt tube amps on 96db/Watt. So I'm definitely on the "too much power" side, and it works extremely well; I love it. The system gain structure is a little suboptimal, but that's a (kinda) different issue. |
The tube amps that have the most unique sound compared to the norm are probably those made well and with little or no Negative feedback applied, like Atmaspheres.
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OK. Let's please get off my "not all Watts are the same" comment. I didn't realize it would be so badly misunderstood - my mistake. Just so it's understood - I'm perfectly aware what a watt is and is not, so let's move on ... |
Wow. Quick first responses! But before this gets too far in, I better qualify that I didn't mean that I'm new to EE or Physics or high-end audio listening. However, I am new to tubes as they're used in audio equipment. So my question is only partially about the physics/engineering behind tube implementation in audio. I realize that theory and circuitry may very well be part of any good explanation, so I don't want to discourage it. But the main question is about what tube enthusiasts like to hear and how they achieve that sound at their preferred listening levels.
I think Atmasphere understands where I'm coming from. In fact he/she may have answered part of my question, but I'd like to hear other viewpoints.
Mapman, I'm sure you have some good insight now that (hopefully) I've explained a bit better. I'm sure you know more about the subject than me and I look forward to more input from you. However my question is more subjective than came across. How does a tube enthusiast choose the right power for their system given that they actually may prefer more distortion of the right harmonics? If they choose a higher power amp I'm assuming (and yes I might be wrong!) that there will be less of the DESIRED distortion that adds to the fun of tubes.
Czarivey, I appreciate the input but you misunderstood the point that not all watts are created equal. They most certainly are not, or we'd all have $200 Bose equipment and stop there. |
Look, solid state uses electron junctions that are squished inside doped silicon. In tubes, electrons are free and happy. All Watts are the same ;-) |
Note that most tube amps (and some SS amps) soft clip which is why fewer watts seem to go further. But the clipping still occurs, though it will take more volume before the results become clearly unpleasant. But any clipping is distortion. You loose dynamics whic is what adds the excitement to a lot of music. If you don't care about that and only listen to small ensemble chamber music, you might be fine, but eventually you may realize what you are missing and look elsewhere. |
Public Enemys (of good sound):
1) room acoustics
2) amp clipping
3) choose your poison |
Clipping is the most common and pervasive form of distortion in most cases.
Unless you only listen at very low volumes, there is a very good chance that clipping and related forms of distortion will come into play and degrade sound quality in ways that might not be very apparent.
Its not that hard to avoid clipping. Just do not use an amp that is underpowered to drive the speakers. Use more power not less as an insurance policy. Most speaker manufacturers understate the power needed to drive their speakers optimally in order to keep markets open.
If your speakers are even moderately efficient, that helps a lot in terms of choosing an amp that is up to the task.
If you will only listening at low volumes, then none of this matters all that much. The world is your oyster and almost any amp/speaker combo might do.
Once teh amp is up to the task of driving the speakers OPTIMALLY, then you are in a position to determine what other remaining forms of distortion to choose among based on what you hear. |
Further, the topology of the circuit says a lot about what sort of distortion it will make. For example, a push-pull amplifier with a single-ended input will make primarily 2nd ordered harmonic distortion, but will also have some of the 5th. If the amplifier is fully differential and balanced, the primary distortion product will be the 3rd harmonic.
If negative feedback is applied whether tube or solid state trace amounts of the 5th, 7th, 9th and beyond will be added.
At any rate loudspeaker efficiency is important when dealing with tubes, as tube power is more expensive than transistor power! Its important with any system to avoid distortion but in fact distortion is the name of the game as the human ear translates distortion into tonality- this is why transistor amps tend to sound bright, even though the distortion is very low, what distortion is present tends to be the odd orders, to which the human ear is particularly sensitive.
A lot of push-pull amplifiers will actually make more distortion below a certain power level, so for those amplifiers its helpful to have a speaker that is a little less efficient, so the distortion is happening at a lower level and is hopefully less noticeable. But this is why some amps seem to lack detail at lower power levels.
There is definitely more to this than meets the eye! |
I just went through this exact same question myself when trying to decide on amplification for a new system. In my case the speakers are rated for 100 watts. The amp I picked is tube and rated at 140 wpc. It sounds fine. Almost effortless. Would it sound even better with double the power? That would give me 3 db of additional headroom, a barely perceptible difference. As already explained clipping is bad, in addition to adding significant amounts of IM distortion, clipping can damage your speakers. Here is what I would do. Determine the sensitivity of your speakers. This is stated as so many db at 1 watt input, measured at 1 meter away. Then calculate how much power you need for the sound pressure level that you want to achieve. Every doubling of power adds 3 db. So for example: Assume the speaker sensitivity is 90 db at 1 watt. 2 watts = 93 db, 4 watts = 96 db, 8 watts = 99 db etc. Then add 3 db to your assumed max listening level for safety. Make sure your speakers can handle the power you calculate. |
How things distort is one aspect that varies with different amplifiers but is only one aspect of performance of sound.
How much power is needed to drive any particular pair of speakers is mostly a function of recording quality and SPLs (how loud you listen).
For optimal performance, it is almost always a good idea to have more power than needed rather than less.
Clipping is always public enemy #1 when it comes to amps and speakers. you want to avoid clipping at all costs in that it will only compromise the sound quality to various degrees.
The only way to avoid clipping is to have more than enough power than will ever be needed to drive the speakers OPTIMALLY.
Having said that, optimal performance is a good first goal but alone does not assure "sound quality". Personal preferences come into play when talking about what sounds "good" . Optimal performance is always a good thing but alone does not assure you will like what you hear, though the chances are best that you will for sure.
So always strive toavoid clipping no matter what first. Then decide on your favorite flavor of sound from there. |
Power can be Electrical [Watts] or Mechanical [Joule per second]
In Both cases it's an amount of work delivered per given time or an amount of charge delivered to the load per given time.
The meaning of electrical power delivered to the load is absolutely the same no matter what source of power exists. |
