why tube amps are perceived "stronger" output than SS

fredv

I have seen quite a few times that a tube amp has certain wattage rated output power is equvalent to a SS amp that is rated at double the wattage. For example, a 75wpc tube amp is just as good as a 150wpc SS amp. Why is that? Does this have anything to do with voltage amplification and current amplification? Any other question is that sometimes many of you say certain speakers love high current (e.g. the lsi9,lsi15),does mean tube amp is not suitable to these speakers as tube amp raise the voltage to increase the wattage instead of the current?

dragon1952

I don't have an answer but I have noticed that my new tube integrated at 50wpc sounds every bit as powerful as my old 125wpc solid state amp. That's with relatively efficient 8ohm speakers of course. Don't know how it would compare with harder to power speakers.

ND13

From what I understand, it has to do with SS amps using current to drive the speakers and tube amps using voltage. I hope that's what I understood.
So what you said seems to be correct.

SCompRacer

I don't know that a formula exists for determining the equivalency. I'm sure the guys with tube and SS amp experience could offer a solid opinion on that.

True, the tube amp makes it's wattage with higher voltage versus the SS amp doing it with current flow. I don't have to go any higher with the gain knob on my pre for equivalent volume with my 75WPC tube versus my Rotel. Some tube amp guys say speaker cables don't make as much difference with higher voltage wattage than they do with higher current flow wattage. Makes sense, but I haven't tried that yet. Following that thought, impedance output in pre amps probably determines the differences in sound one hears with interconnect swapping.

McAlister tells me electrostatic speakers are some of the hardest speakers to drive. He built a pair of 280 WPC OTL monoblocks to drive a pair of custom made electrostatic speakers. Together, they pull 30 amps.

fredv

What puzzles me is that one tube watt seems to be stronger one SS watt, but one watt is supposed to be one watt

heiney9

fredv wrote:

What puzzles me is that one tube watt seems to be stronger one SS watt, but one watt is supposed to be one watt

Best simple analogy I can come up with is Horsepower. 1hp = 1hp same as 1 watt = 1 watt. It's the way the (hp) and watt is used that makes the difference. There are many other variables to consider. Too many to list and I'd need to get my learn again to be able to explain it in a way that was coherent.

So to answer your ? yes a watt is a watt.

H9

AsSiMiLaTeD

A watt isn't necessarily a watt - what's polk's little ditty 'not all watts are created equal'...

Remember the formular for watts? Watts = Volts x Amps. So watts is the product of voltage and current. If an SS amp makes watts by increasing the current but tubes create watts by increasing the voltage more (need to verify), you're going to get a different end result - because there's a different proportion of the components.

Let's say I make a cake that's 4 inches thick. If I make one cake with 3 inches of dough and 1 inch of frosting and another with 1 inch of dough and 3 inches of frosting, they're both still cakes - but will taste completely different...

I'm hungry

heiney9

My only point is; it IS a unit of measure, just like horsepower. Theoretically 1 watt = 1 watt that is a mathematical certainty using Ohms law. Mathematical equations don't take into account the real world variables, that was the point I poorly tried to get accross. Just like 300 hp in a Ferrari is different than 300 hp in a Chrysler 300M. The formula for calculating HP is the same but the real world results are completely different. That's all I'm trying to say. I've hit the bottle a little early this weekend so maybe I'm talking in less than a straight line.

H9

PolknPepsi

ND13 wrote:

From what I understand, it has to do with SS amps using current to drive the speakers and tube amps using voltage. I hope that's what I understood.
So what you said seems to be correct.

From what I've been told by a maker of tube preamps, Noel hit the bullseye with the current/voltage thing.

SCompRacer

A watt is a watt but there is a difference in how you get there.

A simple and crude anology. Think of the output transformer on the tube amp like the ignition system on older cars. The points open and you get output from the ignition coil. But a constant flow of direct current through the primary windings of the output transformer won't induce any output in the secondary windings to your speakers.

You have 430 volts of DC from the output grid of the tube connected to the primary windings of the output transformer. You need AC voltage to make output in the secondary windings. Enter the audio signal, which is AC. The points open, and now you have a linear output to the speakers instead of a flood of current flow.

Folks talk about soft clipping on a tube amp. What actually happens is if input voltage goes too high, the tube no longer outputs anything.

SCompRacer

Polkmaniac wrote:

..... but tubes create watts by increasing the voltage more (need to verify),

Thats how it's done.

fredv

heiney9 wrote:

My only point is; it IS a unit of measure, just like horsepower. Theoretically 1 watt = 1 watt that is a mathematical certainty using Ohms law. Mathematical equations don't take into account the real world variables, that was the point I poorly tried to get accross. Just like 300 hp in a Ferrari is different than 300 hp in a Chrysler 300M. The formula for calculating HP is the same but the real world results are completely different. That's all I'm trying to say. I've hit the bottle a little early this weekend so maybe I'm talking in less than a straight line.

H9

The automobile's horsepower analogy is actually qute good. It is like 300 horse power with 300 lb/ft@2000rpm and 300 horse power with 200lb/ft@5000rpm. The one with higher torque will definitely be more lively than the other. Maybe voltage to a speaker is like torque to an engine ....

unc2701

Two things
1)There's only on SS current source amp that I know of- Nelson pass's Firstwatt project
2)Maybe it's got something to do with how much more you pay to get 75 tube watts vs 150 SS watts

madmax

With either tube or SS a 25 watt average is very loud. When playing something which has a 25 watt average you end up with peaks in the 300 watt range. These are very quick peaks. If you are using a SS amp you never want to clip because it sounds horible. If you want to have an average level of 25 watts you better have 300 SS watts available. Remember, clipping causes intermodulation distortion which you can easily pick out if it is in the 0.001 percent range. That is because it does not match the fundamental sound. It actually clashes with the fundimental sound, just like hitting two keys next to each other on a piano.

Now, enter the tube amp. It is playing the 25 watt average. It too wants to shoot up to 300 watts on the peaks. Obviously it can only hit 50 watts so that is when it distorts. The distortion is different though. The distortion matches harmonically with the fundimental. This type of distortion is called harmonic distortion. You can easily pick it out once you get above 20%. Not only that but much of the peak is just ignored by the tube and no sound is output. Pretty much you can play that 25 watt average and it sounds similar to the 300 watt SS amp with the exception of intermodulation distortion being lower.

If you followed along so far you can probably see why a tube watt is different from a SS watt (if you want to state it that way).

Now, to throw a wrench into the mix. The previous example assumes the average dynamics contained in the majority of music. There are other cases though. If the music is extremely compressed (lots of metal or hard rock music where you can't even see the power meters bounce around) we enter a more favorible case for the SS amp. Now a SS watt really does equal a tube watt. Of course the SS watt still contains more intermodulation distortion but now the 50 watt tube amp is pretty much equal to the 50 watt SS. The 50 watt tube amp is absolutely no match for the 300 watt SS amp now. This is partly why people with different tastes may prefer one over the other. Personally, I HATE really compressed music anyway.

madmax

audiobliss

So if you listened to rock and pop (which you seem to be saying is compressed), you wouldn't want to use a tube amp?

SCompRacer

Just a pic.

madmax

audiobliss wrote:

So if you listened to rock and pop (which you seem to be saying is compressed), you wouldn't want to use a tube amp?

Actually, rock and pop is fine. It is more the VERY HEAVY metal and rock although compression doesn't necessarely go hand in hand with a genre. Pretty much if you start the song and hear absolutely no change in sound level whether it is a cymbal, a drum, a guitar, a voice, whatever, then it is compressed. Another way to tell is if there is no quietness between sounds.

You can tell what is compressed and what isn't. :rolleyes:

But yes, if the source is all compressed it will probably sound better on SS. Of course you miss the glow. :eek:

madmax

mldennison

so i did a little searching in the forums after reading whtat madmax said and found this thread which goes into alot of detail leading up to the conclusion madmax makes:
http://www.polkaudio.com/forums/showthread.php?t=4451

this then lead me to some cool outside links about harmonic distortion, here is one showing the effects on a sine wave:
http://members.aol.com/sbench102/thd.html

and here is one you can actually hear:
http://www.pcabx.com/technical/nonlinear/index.htm

mike

fredv

Off topic a little bit, why tube preamp + SS is recommended more than SS preamp + tube amp? It sounds like SS preamp + tube amp is more desirable, based on the above discussion.

madmax

Although I like tubes in both places if I HAD to choose I would prefer the SS pre with the tube amp. You just can't beat tubes on the output. However, I know where others are coming from. They want more sound pressure or hard hitting dynamics than the 50 or 60 tube watts give them. I totally understand and have migrated from that. I still hook up some solid state muscle from time to time for a thrill (and it is quite an awesome time) but truthfully after 30 to 45 minutes I'm ready to shut it down. It's funny but I end up with music on and some critical listening almost every evening when the tubes are connected but go for weeks without being interested when the SS stuff is up. I've even found myself walking over to the system to turn it on then deciding not to. That never happens when the tube amp is connected. Certainly they both have their own merits.
madmax

hellohello

hmm... i remember hearing that its the way the two distort that makes them sound different, the tubes have a more pleasing distortion when over powered that makes them seem louder than ss, which has a harsher distortion due to its on-off-on non-compressing nature

Jstas

Yes, the pleasing distortion is the harmonic distortion.

The reason that the tube amps will seem more powerful is not because of harmonics or whether a watt is a watt. They seem more powerful because SS amps have a much harder clipping curve than the tube amps. Because of the analog nature of the amps, they gradually progress into a full clipping state rather than SS amps which have a rather abrupt entry into clipping.

Because of that and the fact that tube amps have the harmonic distortion, you can push a tube amp past the point where it starts to clip and not hear the distortion. This gives the impression that the tube amp is more powerful at a given wattage than a solid state amp at that same wattage. It's not any more powerful, it can just play audibly cleaner into a clipping state farther than a solid state amp can. that doesn't mean it is playing cleaner, you just can't easily hear the distortion that is present.

From what I am told though, harmonic distortion is less likely to damage a speaker than the intermodulation distortion that a solid state amp will experience. How true that is, I don't know.

madmax

Another thing tube amps do well is play multiple sounds at the same time. For example, take 50 different sounds all played at the same time. On a SS amp, unless it is an exceptional one (read super expensive), you will hear a barage of sounds but they all melt together and make it very hard to pick out one single sound out of the mess. Not so with a decent tube amp (read average quality affordible one). In the midst of all the sounds you can hear each one seperately. This is a big part of my excitement about tubes. More so than the distortion thing. This is especially evident when played on SDA's with material which space the different sounds over an even wider soundstage.
madmax

madmax

Oh WOW! I just noticed I'm over 5K posts and have become a Polk Master!!! I should be called the Tube Master or Tube God or something appropriate. Bow down before me as I am PolkMaster...
madmax

audiobliss

So far from reading this thread I've gathered that tubes exhibit a harmonic type of distortion that allows them to be pushed into clipping, though not audibly, and thus they seem more powerful than SS amps because their intermodulation type of distortion is readilly audible. However, I haven't read if you can take advantage of the tube amp's harmonic distortion. Is there anything bad about driving a tube amp into clipping? It makes sense that there's a point you don't want to cross, but is it generally acceptable to drive a tube amp into clipping? Will the amp or speakers be damaged?

SCompRacer

madmax wrote:

Oh WOW! I just noticed I'm over 5K posts and have become a Polk Master!!! I should be called the Tube Master or Tube God or something appropriate. Bow down before me as I am PolkMaster...
madmax

organ

That's an excellent explanation, Madmax!

One other thing I noticed with tubes vs ss is their sound characteristics. With music being played at the same volume, the tube amp always sound more powerful in my rig. The reason is because the sound is warmer, richer with more body. This makes the tube amp sound more powerful especially on upper bass. However, a ss amp will sound more powerful on deep bass.

Audiobliss,
You don't want to distort a tube amp. It will soft clip which is more desireable than hard clipping from ss, but you'd want to stay within their linear operating point unless you're a guitar player.

This is a very interesting thread.

Maurice

audiobliss

Then that leads to my next question: If tube amps distort in such a way that the distortion is not readilly audible, how can you make sure you don't turn your amp up til it clips?

Jstas

Distortion of any kind will generate excess heat. Heat will kill tubes and shorten the lifespan. Yes, they do run hot anyway but they are supposed to. Excessive heat will kill any gear.

However, the other probelm with clipping is that it can cause the amp to draw more power than it's power supply is capable of feeding it. When that happens, two things can happen. For one, you can toast the power supply. More likely though is that you will blow a tube or burnout a diode. This is also usually why tube amps, unless they have special switching circuitry, will only handle a single impedance. Granted, with today's range or impedances on speakers, most modern tube amps I have seen are capable of anywhere from 24 ohms to 2 ohms of stable operation.

Distortion is bad in any respect. However, you can feed a speaker distortion as an audio signal all day long and as long as the gear is not clipping and feeding clean power, the speaker will play distortion just like it would music. Well, let reprhase that. It will play the sound that distortion makes without a problem as long as the amplifier or signal source are not clipping.

Then teh questions remains, if you are playing distortion sound through your speakers, how can you tell when you gear is clipping and causing distortion?

bikezappa

Why do tube amp watts sound louder than SS amp watts?

Try this.

Most of us never even come close to using the total amount of watts from any amplifier. You can prove this by measuring the voltage across the speaker terminals to calculate the watts driving the speakers.

Watts = voltage times amperes

Amperes = voltage divided by resistance or impedance of your speakers

Therefore Watts also = voltage times voltage divided by resistance

Remember that math course in high school?

If you can stand to listen to music at 20 volts across your 4 ohm speakers you will be using 20 times 20 divided by 4 = 100 watts. That is pretty loud. Most tube or SS amplifiers never get any higher than 100 watts to the speakers.

There is also instantious power and peak power which you can't measure with a volt meter, need an oscilliscope.

Maybe tubes just sound different at similar power levels. Or a 75 watt tube amp sounds like a 200 watt SS because they are both driven with only 75 watts anyway.

Sorry for the math stuff, but you may need data and ohms law to figure out stuff rather than just sitting and guessing.

Hope my math is correct.

madmax

They fall apart just like a SS amp. When it's too loud you know it. It isn't as harmful though because it is harmonic distortion and of course it is only 50 or 60 watts generally. I have on ocassion played some things too loud and enjoyed the big ballsy distortion sound on particular songs. This is just slightly above clean, not obsessive. I don't recommend going too far because of your tweeters.
madmax