Tube watts Vs. Solid state watts (1 Viewer)

[Yogi]

Here is the link to an ear opening article about why tube amps sound louder than comparable power SS amps.

http://www.stereophile.com/printarchives.cgi?357

 

[Seth_L]

Well, he missed the boat...

Repeat after me. 25W is 25W is 25W.

All he proved is there's extra output resistance in the tubes that lowers the current and raises the voltage of the output because it doesn't saturate as quickly. Nothing magical.

 

[Yogi]

Well Seth, with all due respect, I think you missed the boat in that article. I think there is more to it than just the output impedance of the tubes. You forgot the 'output transformers' that interact with the speakers and not the tubes. Also all it shows is why tubes sound louder than comparable transistor devices and nothing about 25W from a tube amp being larger than the 25W from a transistor amp. Do I need to elaborate?

Also please lets not degrade this thread into an objectivist and subjectivist sound issue. Lets just keep it simple like its meant to be.

Thanks,

 

[Scott_N]

Who cares about numbers as long as the amp will drive your speakers at a loud enough level for your taste and sound good to your ears.

 

[Chu Gai]

Elaborate si vous plait

 

[Bob_M]

>Who cares about numbers as long as the amp will drive your speakers at a loud enough level for your taste and sound good to your ears. <

Your right if we were all normal listeners who enjoy music and movies. But we are HT enthusiasts, we don't care about the movie, we want to know how we can rattle our neighbors windows with duel SVS's

Just kidding here but my point is, as enthusiasts we want to know a little more about how the gear works than the average listener.

Bob

 

[John Garcia]

Dual SVSs driven by 25w tube amps? j/k

I find it a very interesting article.

 

[Scott_N]

I was refering to music listening. For HT I will grant you more wpc help.

 

[Chu Gai]

Well you know, that article leaves a ton of stuff out and it pays to keep in mind that he was running the solid state into something like a 3.5 ohm resistor. However, it's a broad premise and one that doesn't necessarily hold true in all cases. Consider the following posting that was made by Arny Krueger.

Following the usual pattern of poorly-informed RAO trolls and tube bigots, Richman has his facts all wrong and is making a false distinction between tubes and SS power amps.

Traditional tubed power amplifier technology predates the FTC's power rating rules. Tubed power amps were traditionally designed in accordance with the designer's perceptions of what it took to make a good-sounding power amp, as opposed to measured performance on a test bench.

FTC's power rating rules essentially force power amplifiers to have grossly overbuilt power supplies, as compared to the minimal requirements for accurately reproducing music. This results in a power amp that is optimized to deliver maximum undistorted power with resistive loads and pure, steady tones on a test bench, as opposed to delivering maximum power into a loudspeaker load with music in a listening room.

Amplifiers built with traditional tubed power amplifier power supply design parameters may therefore more closely fit the minimal requirements for accurately reproducing music in real world usage. These amplifiers will measure out as having less power, in accordance with the FTC's power amplifier rating rules, but when they reproduce music, they will play louder with low distortion.

So the issue is not a matter of differences in the capabilities of tube technology, as opposed to SS technology, but rather the conventions that are followed when the equipment is designed. Given that many tubed power amps have SS power supplies, and its the power supply that makes the difference, this is clearly not a tubes versus SS issue.

There's nothing that keeps anybody who wants to, from designing a solid state amplifier that has the same kind of relatively low FTC power rating combined with ability to deliver more music power, that is sometimes seen with tubed amplifiers.

Basically, what these amplifiers with greater apparent loudness have, is a more poorly-regulated power supply. Ironically, cheap mid-fi solid state equipment is more likely to be designed this way than more expensive high
end solid state equipment.

So, when you see some golden-eared reviewer ranting and raving about the heft, solidity and excellent power supply regulation of some high end amplifier, he's really admitting that it is designed more to provide impressive performance on the test bench than maximum undistorted loudness in the listening room.

BTW, the degree to which FTC power rating rules mandate overdesigned power supplies for audio power amps is on the order of 200-300%. So, it's not just a little thing.

Course, you could always get a ballsy QSC or Crown probably for less than the tube unit. Then you could toss a 3.5 resistor on that and get some interesting distortion going on.

 

[Seth_L]

Also all it shows is why tubes sound louder than comparable transistor devices and nothing about 25W from a tube amp being larger than the 25W from a transistor amp. Do I need to elaborate?

But that's just it. He wasn't getting 25W from both amps.

P1 = i1*V1 and P2 = i2*V2

V = iR, so we can rewrite

P1 = (V1^2)/R1 and P2 = (V2^2)/R2

Now if P1 = P2 (25W) We can rewrite

25 = (V1^2)/R1 = (V2^2)/R2

But since the speakers are the same in both case R1 = R2 = R

25/R = V1^2 = V2^2

SQRT(25/R) = V1 = V2

So, there you have it... If the amps have the same power into the same load they Voltages are equal.

Since in this case the Voltages aren't equal, each amp isn't putting out the same amount of power. Which means they're not both 25W amps. If they're not putting out the same wattage, of course they're not going to be the same volume.

But please... Elaborate...

 

[Michael R Price]

While the article's measurements prove that tube watts are "louder" than solid state watts, it also proves that tube amps compress the sound (to a significant extent) before clipping. I'm not sure which is better...

 

[Chu Gai]

Well of course, buy what you like.

 

[Seth_L]

While the article's measurements prove that tube watts are "louder" than solid state watts...

I'm not sure how you can come to that conclusion given that the two amplfiers in question did not have same power output.

 

[Brett DiMichele]

Watts Are Watts

What I attribute to the seemingly more loud nature of Tube
Topologies is the fact that Tube Clipping is easier on the
human ears (and the drivers) that a clipping transistor
Topology. Therefore you can drive the Tube Amp futher into
distorsion in most cases with "acceptable" results to most
ears and this would make it seem to be louder when in fact
it is still being driven past it's linear amplification
range it just doesn't sound quite as bad as when the transistor
amp falls on it's face.

Yes/No?

 

[Michael R Price]

Right, Brett and Seth, what I meant was that tube amps clip "softly" so the sound compresses quite a bit (peaks reduced in amplitude) before the distortion becomes objectionable. It is true that a watt is a watt...

 

[Yogi]

Course, you could always get a ballsy QSC or Crown probably for less than the tube unit. Then you could toss a 3.5 resistor on that and get some interesting distortion going on.

I have heard of that one before. In fact Sunfire tried something like that with their amps thinking they would sound like tube amps but they sound nothing like tube amps. They just sounded silly with loose flabby bass. Tube amps dont sound like they do just because they have a high output impedance. My MV-55 has an output impedance of 0.4 @ 8 ohms and it sounds pretty powerful compared to my B&K 7250. In fact I just watched the LOTR(TT) with the mains running (full range W/O sub) off the MV-55 and let me tell you it sounded pretty powerful and dynamic. Modern tube amps dont sound like the amps of old days and are pretty well designed in terms of powersupply, output stages etc. In fact the ARC amps sound closer to SS amps then tube amps, to my ears. They can compete with the best SS designs in terms of bass impact and dynamics.

 

[Chu Gai]

Well Bob Carver to be specific and his primary purpose I think was to introduce some of the characteristics of many tube amps. Note though that I didn't say they sounded like any particular tube amp. Given that tube amps can and vary in output impedance and further more that it's frequency dependent is it any wonder that different tube amps interact differently with the same speaker? I think not.

No one's questioning your preference for one over the other Yogi, but I thought the reason why you posted the article was to perhaps gain some insight, opinions, etc. as to some technical explanations for this oft cited phenomena. No? That both amps measure ~25 watts as per FCC regulations (the usual warm up and 8 ohms resistor) and have quite different power into lesser resistance is hardly a revelation. You yourself know that to be the case from your general experience with solid state. You're also aware that if the output impedance of the amp is sufficiently high it will cause the amp to deliver more power depending upon the impedance of the speaker. In effect this is the same as putting an equalizer on the amp. Toss in a more loosely regulated power supply and really, is it any wonder why the author obtained the results he did?

Further I think it pays to consider a bit the pedigree of the author of that article, Peter van Willenswaard. He is a fan of tubes, valves if you will. Nothing bad about that, but IMHO, rather than stating some of the obvious reasons for what he observed, he faulted the humble 25 watt SS amp for not being able to deliver comparable power into a particular load. Peter could've been objective, sanguine if you will, and instead acted like a typical attorney. Keep in mind this is the same person who sought to give experimental credence to the 'green pens make CD's sound better' camp. I don't question his or your preference for using tubes. I do question his objectivity and the two houses he builds...bricks for one, straw for the other.

 

[Yogi]

Further I think it pays to consider a bit the pedigree of the author of that article, Peter van Willenswaard. He is a fan of tubes, valves if you will. Nothing bad about that, but IMHO, rather than stating some of the obvious reasons for what he observed, he faulted the humble 25 watt SS amp for not being able to deliver comparable power into a particular load. Peter could've been objective, sanguine if you will, and instead acted like a typical attorney. Keep in mind this is the same person who sought to give experimental credence to the 'green pens make CD's sound better' camp. I don't question his or your preference for using tubes. I do question his objectivity and the two houses he builds...bricks for one, straw for the other.

I see your point Chu. I would however like to see a comparison between a SS Mac and a comparable tube amp to see if its the impedance matching transformers have something to do with this.

 

[Michael R Price]

This is all very interesting! I have one question, though: are there any measured differences between amplifiers using "good enough for music" power supplies versus those able to deliver full power continuously?

 

[Chu Gai]

I think more so than the output transformers Yogi it may have something to do with the implementation or not if you will of feedback, the nature of the tube topology, the power supply (as mentioned above), etc. But one could equally as well ask a similar question of solid state devices. Why is it that with three amps, all 100 watt/channel, are there different outputs into say 4 ohms, or 3 ohms? Tough question but I don't know if it's necessarily worth agonizing over. Certainly it's not going to be due to one particular component.

A problem or a deficiency, as I see it, is that we don't see enough measurements of devices into real world loads for amps in general. I think some magazines do a pretty good job with speakers and all, but when it comes to amps, it seems to fall woefully short. The consumer doesn't have a good understanding of how the amp will behave if the impedance of a speaker is low on the low frequency side as compared to if it's low in the upper frequencies. The ability of the preouts aren't investigated with respect to driving long lengths of interconnects for those people adding amps.