[FullRangeMan]

Watts is a variable moody lady, its a changeable thing like the wind, in the hey days of Solid State amps in 1960/70s it was used to marketing purposes.

These are some kind of Watts used in audio over the years, maybe there was more:
W continuous
W peak
W RMS
W AES
W IHF
W PMPO

[InfernoSTi]

Per Docere's comments, let's say a bit more here than just the normal "watt is a watt" which is true but not really the point.  The circuit interaction with the speaker impedance is the reason the two sound differently.  Super simple once you walk through the basics.

Here is a nice discussion of the difference you are likely to hear between tubes and ss (related to how the "power" is used):

Valve amp: power is directly proportional to speaker Impedance therefore power increases as the speaker Impedance rises.

Solid-state: power is inversely proportional to speaker Impedance therefore power decreases as the speaker Impedance rises.

http://education.lenardaudio.com/en/14_valve_amps_7.html

This has a lot more to do with how the two amps sound and how they perform, watt for watt. 

Not all SS are the same, either.  The discussion of Class A vs A/B, etc is really important. Simplified to a high degree, splitting the signal/wave into two parts vs. leaving it a whole wave is the issue. A/B or Push-Pull circuits are not as pure sounding as Class A.  This seems to be a lot more important than the harmonics issue (even vs. odd harmonics when distorting) since the amp should be paired with speakers that allow headroom at 105 db.  If you are driving it to distortion, then perhaps the issue is speaker/amp selection, not tube/SS selection.

But if you have headroom and you have linear components and you are simply choosing tube vs. ss, then Class A vs A/B is really important.  Pass Labs/First Watt is based on this idea and is a good starting point for discussion.

One of the unfortunate things is that we generalize.  So my three main amps for my system are Bottlehead Paramount 300b which uses a parafeed/constant current circuit (not your typical tube circuit), Pass Labs XA30.5 which is low watt SS in class A, and Quicksilver Silver 88 tube amps which are a unity-coupled circuit (like a McIntosh MC275).  Parafeed and unity-coupled circuits are worth a look if you are worried about Class A tube amps not having damping and thus bloated bass...they both solve for this in different ways that sound great.   Details matter, not generalizations, when it comes to amps.

Best,
John

[Steve]

Per Docere's comments, let's say a bit more here than just the normal "watt is a watt" which is true but not really the point.  The circuit interaction with the speaker impedance is the reason the two sound differently.  Super simple once you walk through the basics.

Here is a nice discussion of the difference you are likely to hear between tubes and ss (related to how the "power" is used):




http://education.lenardaudio.com/en/14_valve_amps_7.html

The article is not entirely correct and problems elsewhere as well. Even in tetrode mode, the output impedance (Z) is not infinite/constant current, so power does not rise linearly. Almost all push pull ultra linear and PP triode type amplifiers, without global negative feedback, have the power dropping as the speaker impedance rises, and have damping factors of ten or even more, so they are voltage based. Remember, the goal is flat response with optimum system Qts of ~ 0,7 or so.

And it is possible to have near perfect, if not perfect accuracy from a puch pull (pp) triode (KT-88s in triode mode) amplifier. This via special listening tests in the lab. It is the responsibility of the speaker designer to design for optimum frequency response for a given amplifier output impedance.

This has a lot more to do with how the two amps sound and how they perform, watt for watt. 

Not all SS are the same, either.  The discussion of Class A vs A/B, etc is really important. Simplified to a high degree, splitting the signal/wave into two parts vs. leaving it a whole wave is the issue.

That belief is one of the big myths out there. A proper phase "splitter" simply takes a gain stage and divides the output musical signal into 2 signals, each signal is still a full wave, one signal for the "upper" tube and one for the "lower" tube. It is the circuit that is nearly always misdesigned. But that is the designers fault, and the particular circuit used. One does not design a circuit with a couple of equations. Not that simple.

True, the solid state "splitting" circuits are often more complex/inferior, but we cannot generalize all together. Again, if a designer cannot tell a good circuit from a bad circuit, that is his/their fault. The circuit design is no worse than a typical gain stage in any amplifier, if done and listening tested correctly, as with any gain stage.

A/B or Push-Pull circuits are not as pure sounding as Class A.  This seems to be a lot more important than the harmonics issue (even vs. odd harmonics when distorting) since the amp should be paired with speakers that allow headroom at 105 db.

Another myth. What we are after is accuracy/naturalness. Besides me (PP KT-88s in triode mode), others have designed amplifiers that are virtually perfectly accurate/natural, via special listening tests, not just measurements, and are AB type designs. So .............

But if you have headroom and you have linear components and you are simply choosing tube vs. ss, then Class A vs A/B is really important.  Pass Labs/First Watt is based on this idea and is a good starting point for discussion.

Again, depends upon the amplifier design. Almost all A/B amps are class A for several watts out anyway, and 25 or way more watts of AB can be virtually if not perfectly accurate/natural, if designed with special listening tests performed to adjust and confirm.

I won't comment on the rest. (Been retired for over 5 years now.)

cheers

steve

[demodisc9]

Good evening,

I rarely post by design but I would also like to believe I can contribute. I've owned SS and tubes, more than my wife should know:) I  am also not an EE but have been doing this reproduced audio thing for 45+ years. SS is voltage based, tubes are current based. So,  if you were to ever have touched bare wires from a simple outlet in your home, that is current. Conversely, if you were to ever touch the terminals of a simple 9 volt(age) battery or even larger, you will  not feel anything. I also know that most of us as children, may have been coaxed to do harmless, foolish things with a 9 volt battery in order to have an effect, think as you will.
At the end of the day, you will not want to touch the bare wire from the outlet, again(I would think). Tube amps are "live" with current and you would not want to touch their innards until they have been powered down for awhile. A SS amp will not retain the same type of "current", by design and frankly, you can be a bit more cavalier with.

Tube amps are not more powerful, just more immediate, in my humble opinion.

Mike

[FullRangeMan]

Thanks for the post Steve, I feel less dumb now

[FullRangeMan]

SS is voltage based, tubes are current based.

Hi Mike,
Are you shure this?  I have seem many SS amp with lots of current as 40A in this Odyssey:
http://www.odysseyaudio.com/products-khartago-stereo.html
But I have never seen a regular 10-20W tube amp with this current figure, just its tension are hi.

[Steve]

Hi Mike,
Are you shure this?  I have seem many SS amp with lots of current as 40A in this Odyssey:
http://www.odysseyaudio.com/products-khartago-stereo.html
But I have never seen a regular 10-20W tube amp with this current figure, just its tension are hi.

You are correct FRM. RCA Radiotron Designers Handbook, 26 engineers, 1960, page 558, calls a triode amp basically a voltage source, not current source.

A triode applies nearly constant voltage across the load impedance.

The OPT changes from high signal voltage / low signal current to small signal voltage / higher signal current.
The ratio depends upon the amplifier, but let's say around 15:1 ratio. The output signal current is some 15 times higher than the signal current at the output tube's plate. The output signal voltage is some 1/15th that of the signal voltage at the output tube's plate.

cheers

steve

[InfernoSTi]

Thank you, Steve, I have much to learn still (as ever).  So do I take it that you are saying that the speaker and the amp, regardless of class type, need to be suited to each other based on the impedance requirements of both the amp and the speaker?

That would imply that there are at least tendencies of amp types and speaker types that should be known.  And what are these tendencies?  Class A vs A/B might have different tendencies on their own, right? Some might be more suited for a certain speaker type's tendencies. 

Help me understand how you would summarize what you me, please?  If you don't want to because this is an old retread, no worries...life is short and fun is important!

Best,
John

[SET Man]

Hi Guys,

Been hearing that tube watts are more "powerful" than solid state watts. In fact...it happened last week...oh these speakers are fine with 25 watts tubed. However with solid state...double that. I should know this after so many years in the hobby...but I really still do not. 

Is this true? How does it translate sonically and on clipping issues?

Thanks for your help.

Hey!

    Not an electrical engineer nor audio expert here. Here's my journey in this so called "Hi End Audio" watts wise starting from my first amp...

  60wpc SS with 6Ω 86dB speaker > 250wpc SS with 6Ω 86dB speaker then with flat 4Ω 85dB speakers (guess what speakers) > 100wpc PP tube with flat 4Ω 85dB speakers > 18wpc SET with flat 4Ω 85dB speakers > currently same 18wpc SET as before with 94dB single driver speaker since 2002. And now I have a 40wpc SET around too.

   Funny that my current amps are less powerful than my first amp. I don't know why people say tube sound more powerful than SS at the same watt rating. Probably due to how tube amp handle the load and gentle clipping. But I have to say that at least with tube I don't have to worry about clipping killing my speaker when I drop my needle on my turntable and etc. Clipping wise my I once or twice when my neighbors weren't home tested my 18wpc SET into 85dB speaker and they would just run out of steam, I could see bias meters moving. No damage to speaker what so ever. And it was louder then I ever want to listen.

   Anyway, power discussion aside, tube just sound better to me! No, don't get me wrong I've heard some nice SS amps too over the years but at the end of the day I always come back home to my SET amps. Oh! Well, whatever floats your boat man.

Take care,
Buddy

[Steve]

Hi John,

I will attempt to answer your questions in order.

Thank you, Steve, I have much to learn still (as ever).  So do I take it that you are saying that the speaker and the amp, regardless of class type, need to be suited to each other based on the impedance requirements of both the amp and the speaker?

Yes, it is kind of a blur, optimum matching of speaker design and amplifier output. Of course optimum does not mean that you will obtain the best, most natural sound; just optimum for that speaker amp match. 

That would imply that there are at least tendencies of amp types and speaker types that should be known.  And what are these tendencies?  Class A vs A/B might have different tendencies on their own, right? Some might be more suited for a certain speaker type's tendencies.

A blur to some extent. Generally, but not always, class A tube single ended amps have higher output impedances (Z) than other amps, so the speaker design would be, generally, different. But when one gets into typical amps with lower output Zs, there are more common type speakers available. But then it also depends upon the speaker type as well. So it can be a crap shoot.

Here is one for you. Tube type amps are known for flabby bass, but there are tube type amps that are tight in the bass, even without negative feedback applied. It is all in the amp design. Of course if the speaker is known for flabby bass (improper total Qts) not much can be done.

Cheers

steve

[Docere]

Here is one for you. Tube type amps are known for flabby bass, but there are tube type amps that are tight in the bass, even without negative feedback applied. It is all in the amp design. Of course if the speaker is known for flabby bass (improper total Qts) not much can be done.

Agreed! My latest SET amp has a roughly 2R output impedance, uses a wimpy low-gm pentode input/driver, is currently running the softest output tubes I have in my stash (Shuggie 2A3C), and puts out a massive 2W. But, its PS is designed for low impedance at audio frequencies and fast, clean recovery; it's directly-coupled; the output tube runs at about 70% dissipation; all caps are dry-film (nice types for the cathodes); the PS transformer is over-spec'd; and the output tube load is slightly "high", inductance is "high", and the transformer is cruising. I should add that the speaker runs an efficient,  large, low QTS driver and the cabinet design factors in the output impedance of the amp, room size, and proximity to room boundaries. Bass would not be described as flabby by most. Actually, similar to a good SS amp in resolution and subjective linearity... but has flow and more sense of expression, if lacking some punch (compared to big SS on big drivers, not dinky little drivers that nothing can save).

I'm happy with the trade offs in my situation... but would love to hear some multi-woofed driven by higher SS power... or big horn-loaded beastie...

Cheers.

[undertow]

Myth and theory collide.

Truth is most amps really don't vary much by wattage, but due to entire system "Gain".

Theoretically a 100 watt amp with 28 db of input gain vs. a 50 watt amp with 31 db of gain are essentially going to be about the same power out on a volume control of the same preamp plugged in to a point thru the same efficiency speaker, and impedance load. One might sound like it has better bass, or more power which due to many variables with synergy, and current supply can vary.

In the end tube watts vs. solid state watts means nothing. The whole system could sound better with one or the other if properly matched.

I found ultimately the best results for reliability, and long term sound satisfaction comes from good Solid State, but tube amps are fun, and can sound excellent I just never ended up living with them very long for various reasons.

I think everybody needs to experience first hand the different combinations unfortunately as nobody will be 100% accurate how something will sound to you, or in your system.

[kernelbob]

undertow,

I've found that the gain specification of an amp is the least significant issue.  If your preamplifier/attenuator is so intolerant of where the volume control is positioned, then that seems like a problem with the preamp.

I've been biamping my systems for decades now with various amps of different technologies, gain, power ratings, etc..  Different gain and/or rated Watts of the amps is easily addressed by adding a secondary attenuator in front of the amp with higher gain or with higher output level.  Typically, this is the bass amp since that's where higher Watts are appreciated along with higher damping factor.

Much is made of problems with using different amps in a biamped system based on propagation delay.  That's the time the amplifier takes to process the signal from the input terminals to the output terminals.  I've not run that issue in my experience.

Best,
Robert

[undertow]

Kemmelbob,

I think we are talking apples and oranges. I was just explaining why I think most people might be under the impression in some cases a tube amp would sound a bit more powerful in terms of direct comparison with same wattage. Many times they have higher gain so they simply sound like higher wattage when they are not.

Nothing special. Trust me if you take a 22 db input amp vs. a 35 db input you will notice that you must turn that preamp down substantially with the 35 db input. Not saying all have higher gain, some do, some don't. Generally 100 watts is 100 watts, but that does not mean they will output the same at the same volume level in practice it depends on the whole gain chain including sensitivity of speakers.

If you have a phono amp for example in front of your preamp that has 50 db, and then change to a phono with 60 db trust me your gonna have way more output regardless if you up your wattage from 100 to 200 watts in the amp. Same with a 10 db gain preamp, or a 25 db preamp you will have a large difference in gain and output.  Same with amps they will jump up more with higher gain than just chaging about 3db in gain going for double the wattage, or 100 to 200 watts, or 50 watts to 100 watts. This is all I was illustrating in the argument about why some believe tube watts have higher power, generally they have high gain preamps, or amps so it might sound like more wattage at first is all.

[kernelbob]

Hi Undertow,

I use a Tortuga LDRxB balanced passive controller as the main source selector, level setting, and absolute phase control.  It has two pairs of balanced outputs.  I send the output of one directly to Lampizator 211 Balanced monoblocks.  The other output goes to a second Tortuga controller, the LDR1B.  It only has one input, so no source switching.  It's only purpose is to trim down the level of the signal being sent to the Spectron amps which have higher output than the 211's for a give input voltage.

My point is that it doesn't matter how much more volume the Spectrons generate for a given input voltage than the 211 amps since I use the LDR1B to trim the output going to the Spectrons so the bass drivers' output is properly matched to the mid/tweeter drivers' output from the 211.  This also lets me nudge the bass level up or down one or two dB to correct lean or fat bass in recordings as well as increase it a bit for low level listing.

Much more significant in my system is the input impedance seen by the source (Lampizator Golden Gate DAC).  The Tortugas (both units) allow you to select any input impedance from 1k to 99k per phase.  This allows me to maintain a high input impedance that the tubed GG likes.  Right now I'm using 91k per phase at the LDRxB and 96k per phase at the LDR1B.  This protects the signal's "oomph" from being sucked away by the comparibly low 25k input impedance of the Spectrons.

I had Lukasz Ficus of Lampizator set the input impedance of my 211 amps to 100k per phase.  Important to the success of this set up is that the reference output voltage of the Golden Gate is 5v (our higher if the customer wants) since all that "oomph" in the signal has to come from the source.

Best,
Robert

[opnly bafld]

Undertow,
There are forums where many may lack this basic knowledge, I don't think AC is one of them. 

[undertow]

Umm... okay. I opnly bafld I guess I am baffled?

I will say honestly no clue the point of contention here or the listing of specific components kernelbob rattled off doing something specific, or not in his system.

I do understand he disagrees with gain being higher in one system over another has little effect to him in his system whatever that is supposed to mean. Or quote
 "I've found that the gain specification of an amp is the least significant issue."

None of this had anything to do with my general statement about the original posters question on whether or not the tube watts vs. Solid state watts had any relevance so I simply answered with a common mis conception as to why some systems may be perceived to have more 'powerful tube watts'

I guess you guys disagree with this and tube watts are in fact more powerful... great , or higher gain means very little to system synergy.

So if they were not asking on this forum due to lack of knowledge and started the topic for fun I apologize for answering with my experience.

In any case good luck with finding the best combo.

[raindance]

With all due respect I will disagree.
W is just a mathematical calculation, its the result of Tension x Currrent.
So different proportions of Voltage X Current can result in an Watt final.

Example of different structures of a 30W figure:
Amp X 10V x 3Amp=30W
Amp Y 15V x 2Amp=30W
Amp Z 7.5V x 4Amp=30W

So W is an imaginary power figure that does not exist in the electrical reality, what exists circulating in the amps circuits and loudspeakers are different amounts of voltage and current.
Hope this help.

Sorry, but this post is an incorrect application of the formula. In an audio system the power is determined by the current delivery capability of the amp into the load (speaker) being used. You cannot randomly have X amount of current flowing in any old load when applying voltage Y.

The formula you would use is V²/R where V is the voltage measured across the load and R is the nominal impedance of the load.

And yes, tube watts produces exactly the same heating effect (power) in a load as solid state watts. They are exactly equivalent. However tube amps conceal their distortion better because they don't clip hard. They just start sounding compressed.

Also, tube amps SOUND different into speaker loads as they have higher output impedance and therefore their frequency response will vary into the load more drastically than that of a solid state amp.

But it is also OK if you don't believe in physics,, each to his own 

[JLM]

Another basic physics lesson we need to keep in mind: sound pressure level (spl) or dB of gain is a logarithmic relationship to power (watts).  So here's some examples:

1 watt      = 0 dB of gain
2 watts     = 3 dB of gain
4 watts     = 6 dB of gain
5 watts     = 7 dB of gain
8 watts     = 9 dB of gain
10 watts    = 10 dB of gain
20 watts    = 13 dB of gain
40 watts    = 16 dB of gain
100 watts   = 20 dB of gain
1,000 watts = 30 dB of gain, etc.

dB of gain can be added to (accurate) speaker efficiency rating (dB/w/m) to get an idea of small/near-field spl's (assuming speaker and amp are rated at the same nominal impedance).  Agree with poster above that 105 dB is a minimum goal.  Again, amp/speaker synergy, damping factor, power supply 'beefiness', etc. must all be factored in as well so this is just a numbers exercise, but one that is hard to ignore.

[opnly bafld]

I agree with 150 dB as a minium.