Tube amp power watts equivalent to Solid State?


I have a Cayin 35 watts tube amp. What is its equivalent to a solid state amp?
50jess
LOL! You're kidding right?
What is heavier....10 pounds of cotton or 10 pounds of gold?
Into what impedance?
10 pounds of lead!
Here we go again. Popular audiophile folklore, now taken as fact, and now asked to be quantified in some measurable formula.
Well, does anyone out there have a tube watts to solid state watts conversion table? I wouldn't be too surprised.
C'mon guys, everybody is entitled to getting started on this hobby at some point. And we all know there are a number of confusing aspects of it.

50jess, I'm certainly no specialist, but here's one explanation in layman terms.
1 Watt is 1 Watt...equals to 1 Amp x 1 Volt, or any combination of AxV equating 1 W. Hence the above sarcasm. However, there is no established standard for how this is measured by the various manufacturers, and then some amps work at relatively low voltage delivering high current, and others vice versa. And some speakers need high current while others don't. It all depends on the design, and on how the manufacturer decides to rate the amp at any given power.

So high current amps conservatively rated power-wise are often said to equate to more powerfull amps. Conservatively here is used as a term relative to most amps in the market.

There is not really an answer for your question. Maybe a better way to think about it would be in the context of the speakers you have or you are thinking about having. Generally speaking, you would be looking at higher efficiency speakers, probably at 91 dB/W sensitivity at minimum for a 35W tube amp. But then again, it's not only the sensitivity that matters, but the shape of the impedance as a function of frequency...probably this sounds too complex, but at the end of the day you either want to know what speakers are a good match to your amp, or what amps are a good match for your speakers...and can disregard the reasons if you don't care to get into that mumbo jumbo.

I hope this helps
My 12wpc SET monoblocks (845 output tubes, EL-34 drivers) designed and built by a friend sounded much more authoritative and powerful than the CJ Premier 12 monoblocks (140 wpc) I used to have.

So, for me, this contention -- tube watts delivering something more than SS watts -- must have SOME validity. It may not make sense, but I heard it, at length, playing all kinds of music, in my own system. Ten years later I'm still astonished at the twelve-watters. And my speakers are not of the ultra-sensitive variety.

Fortunately I'm not an engineer or I'd know this couldn't happen :-)
"03-16-14: Dopogue
My 12wpc SET monoblocks (845 output tubes, EL-34 drivers) designed and built by a friend sounded much more authoritative and powerful than the CJ Premier 12 monoblocks (140 wpc) I used to have.

So, for me, this contention -- tube watts delivering something more than SS watts -- must have SOME validity. It may not make sense, but I heard it, at length, playing all kinds of music, in my own system. Ten years later I'm still astonished at the twelve-watters. And my speakers are not of the ultra-sensitive variety.

Fortunately I'm not an engineer or I'd know this couldn't happen :-)
Dopogue (Threads | Answers | This Thread)"

In your case, there may be a different explanation for your results with the SET's. In many cases, low power triode amps increase image size. Images of vocals and instruments just get bigger. Its easy to mistake that for more power.
Dopogue, an apple (pinklady) to apple (golden delicious) comparison?
03-16-14: Dopogue
My 12wpc SET monoblocks (845 output tubes, EL-34 drivers) designed and built by a friend sounded much more authoritative and powerful than the CJ Premier 12 monoblocks (140 wpc) I used to have.

So, for me, this contention -- tube watts delivering something more than SS watts -- must have SOME validity. It may not make sense, but I heard it, at length, playing all kinds of music, in my own system. Ten years later I'm still astonished at the twelve-watters. And my speakers are not of the ultra-sensitive variety.

Fortunately I'm not an engineer or I'd know this couldn't happen :-)
Not necessarily :-)

In addition to ZD's point, what stands a very good chance of having been a major factor, as alluded to by Lewinski and Unsound, is the amplifier's interaction with the impedance vs. frequency characteristics of the speaker.

Many speakers have impedances which rise to extremely high values (e.g., 40 or 50 ohms) at some frequencies in the deep bass region, and also to values of perhaps 20 or 30 ohms in the vicinity of mid-range crossover points. For a given input voltage, the power delivery of a solid-state amp relative to its power delivery into 8 ohms will decrease in direct proportion to that impedance rise, when the amplifier is operated within its maximum power capabilities. Its maximum power capabilities into those high impedances will also decrease dramatically, relative to its 8 ohm rating. Both of those effects will occur to a much smaller degree in the case of a SET amp, and many other tube amps.

It should be clarified, btw, that the CJ Premier 12 is a tube amp. However, it has an output impedance (measured by John Atkinson as 0.87 ohms at mid and low frequencies) that is much closer to being in the solid state camp than in the camp of nearly all SET's and the majority of other tube amps. Everything else being equal, that will cause the Premier 12's interaction with speaker impedance vs. frequency variations to be more solid state-like than that of most other tube amps.

Also, nobody has yet mentioned that the characteristics of the distortion rise that occurs with tube amps as their power output approaches and somewhat exceeds their rated maximum capabilities tend to be less offensive than in the case of solid state amps, i.e., they clip more softly. That can contribute to a tube amp being seemingly more powerful than its rating would suggest.

Also, see this thread, which includes extensive discussion of related issues by some very knowledgeable folks.

Regards,
-- Al
An article from Stereophile from some years ago.

http://www.stereophile.com/reference/357/
Tube amps if my memory hasn't gone on the blink have a higher dynamic headroom, generally speaking, than solid state amps, giving the impression of more power than is really there. IIRC many tube amps have a dynamic headroom of around 3 dB so that's what, double the power?
A point I would add to my previous post: SETs will typically have distortion levels that are vanishingly low when small amounts of power are being delivered, and that increase considerably as their maximum power ratings are approached or exceeded. That kind of variation of distortion as a function of output power can be perceived as an increase in dynamic contrast, which can in turn contribute to an increased perception of "authoritativeness."

Regards,
-- Al
It's a far more valid discussion to explore the differences between tube amp and SS amp sound relative to the odd vs. even harmonics issue. That seems to be where the real meat of this whole perceived loudness thing lies, not helped by statements that "tube watts are louder" (says that right on the Jolida site...silly stuff, but I like my Jolida in spite of this sort of fluff). They're not of course, they're simply different, and more fun. That's right...tube watts are more fun than SS watts...unless you're trying to power a phased array of PA speakers for Lady Gaga...or Lord Gaga...some damn Gaga...
Hey Wolf ... did you catch the news on Lady Gaga's latest gig. Another wacko lady performer in her "act" (if that's what you'd call it) vomits all over GaGa. Yes ... I'm talking fingers down the throat and all the rest that follows.

Where was Gaga when I was young and looking for a wife. GaGa is my dream babe/date/wife. NOT!

Yeah ... she could make one puke. Was she dropped on her head as a baby?? Or maybe forced to listen to odd-ordered harmonic distortion at high decibel levels as child.
Not this week!!
This question comes up on a fairly regular basis and I generally read most of the responses. I understand the harmonic distortion differences when an amp is pressed and the output impedance interaction with the load impedance. I don't understand why the ohms law computation of power in different frequency ranges due to different load impedance has any bearing. As long as the frequency response is unaffected, what difference does it make how much power is being dissipated?
I understand ... the output impedance interaction with the load impedance. I don't understand why the ohms law computation of power in different frequency ranges due to different load impedance has any bearing. As long as the frequency response is unaffected, what difference does it make how much power is being dissipated?
Not sure I understand your question, Bob. The frequency response IS affected by the output impedance interaction with the load impedance.

Best regards,
-- Al
Just don't spend $1k to ground your system,save for really good fuses.
Bob, I look at the relationship between amp type and speakers this way. I suspect we are probably saying the same thing, but just a little differently.

For example, asssume a speaker was voiced/designed to be driven by an amp having a very low output impedance, typically a SS amp. Also assume that the speaker has a ruler flat frequency response if driven by a SS amp, even though its impedance varies as a functiomn of FR. As a result, regardless of whether or how much the speaker's impedance changes as a function of frequency response, and correlatively the amount of current/power the amp produces, the speaker should hopefully have a flat frequency response as a function of frequency -- as posited.

By contrast, if that same speaker is driven by an amp having a "high'ish" output impedance, typically a tube amp like an Atmasphere OTL, then the interaction of the speaker's impedance which varies as a function of FR and the amp's high'ish output impedance will produce sonic colorations because the amp will deliver current/power in amounts that differ from what a low impedance SS amp would deliver.

I'll leave the theory to the EEs, but I believe it relates to Ohm's Law.

Where amp and speaker matching get interesting is in the in-between world. For example, my ARC Ref 150 tube amp has a rated output impedance off the 8 ohm tap at low frequencies of something between .6 ohms and 1 ohm. As a result, there is some sonic coloration if the amp drives speakers designed to be driven by a SS amp, like my Paradigm Signature 8, but the coloration is quite tolerable. Perhaps a tad tipped to the bright side because impedance peaks at 20 ohms at the 2.2K Hz x-over point.

I suppose in a perfect world, a speaker with a ruler flat 8 ohm impedance curve and zero phase angle over its entire FR spectrum would be able to do double duty as both SS amp and tube amp friendly.

Cheers,

BIF
Apologies. As Almarg pointed out, I was comparing one tube amp to another tube amp rather than tube to SS. Duh. Only point, I guess, is that SET amp watts are more potent than push-pull amp watts, and nobody asked about that. Sorry.

To clarify something else, the speakers I've been driving with my 12-watters include ProAc Response 3 and a variety of Gallos, all in the 86-88 dB range.
Actually a pound of cotton weighs more than a pound of gold...
Troy ounce... Its much more in the way they clip.
Al,

Sorry, I should have proofed my post before submitting. It's not clear at all what I was questioning.

I understand that the highish output impedance of tube amps interacts with the load impedance and the frequency response somewhat mimics the impedance curve of the load.

What I don't understand is the relevance of power delivery (or dissipation) with solid state designs. For example, your comment:
Many speakers have impedances which rise to extremely high values (e.g., 40 or 50 ohms) at some frequencies in the deep bass region, and also to values of perhaps 20 or 30 ohms in the vicinity of mid-range crossover points. For a given input voltage, the power delivery of a solid-state amp relative to its power delivery into 8 ohms will decrease in direct proportion to that impedance rise, when the amplifier is operated within its maximum power capabilities.
While that's true, what difference does it make? Are you saying that the frequency response of a solid state amp will be impacted by this type of load?
Bif, my understanding of the differences between a low output impedance and a high output impedance amp is that the voltage drop across the output impedance is relatively small in the low output impedance case and relatively high in the high output impedance case; such that the voltage across the load is relatively constant in the low impedance case and relatively variable in the high impedance case.

It's the variable voltage reaching the load that accounts for the variation in frequency response. This is based on a model of a constant voltage source driving the series combination of the output impedance and the load impedance.

My question regarded the relevance of power in the low output impedance case since I didn't think the frequency response of the amp + speaker was impacted.
Hi Bob,

Thanks for the clarification. Bruce's (Bifwynne's) explanation of my comment that you questioned was a good one, and I think that your understandings that you've described are also correct. In the case of nearly all solid state amplifiers (excluding special cases such as some of the First Watt amps that have tube-like or higher output impedances), the interaction of amplifier output impedance and variations of speaker impedance as a function of frequency will not result in significant frequency response differences as a function of what amplifier is being used.

And I was not implying anything to the contrary in my previous posts. Note the two sentences in my post which followed the ones you quoted just above, especially the second sentence:
Its maximum power capabilities into those high impedances will also decrease dramatically, relative to its 8 ohm rating. Both of those effects will occur to a much smaller degree in the case of a SET amp, and many other tube amps.
My posts were addressing reasons why a tube amp, especially a SET amp, may seem more powerful and "authoritative" than its power rating would suggest. As you'll realize, one of those reasons is that its power delivery into the very large low frequency impedance rise I referred to will not decline as sharply (relative to its delivery into lower impedances at other frequencies) as it would in the case of nearly all solid state amplifiers.

So although the interaction of amplifier output impedance and variation of speaker impedance as a function of frequency will not cause significant differences in frequency response among nearly all solid state amplifiers, with many and probably most speakers it will cause significant frequency response differences between solid state and tube amplifiers, and often between different tube amplifiers as well. As Bruce indicated, if one such combination (solid state or tube) results in flat frequency response, the other one probably won't, unless the speaker has an uncommonly flat impedance curve (although some speakers do have an impedance curve that is flat enough to make this a non-issue).

Best regards,
-- Al
With typical speakers, though the impedance might change, the sensitivity also changes accordingly. A typical quality ss amp will more likely maintain flat frequency response with varying power output to the fluctuating impedance of typical speakers. A typical quality tube amp will more likely deviate from flat frequency response with steady power output to the fluctuating impedance of typical speakers.
Hi Unsound,

I essentially agree, except that I would substitute the words "the majority of speakers" for "typical speakers." I would put it that the majority of speakers are designed to provide flattest frequency response when driven by solid state amplification.

Best regards,
-- Al
There is an issue here that has not yet been discussed. It has to do with something called 'space charge effect' that often occurs in tubes and does not occur in transistors.

First- space charge: this is where a tube is conducting and some of the electrons bounce off of the plate and gather in its vicinity. This usually happens more near the point that the tube is about to saturate, depending on the tube. Pentodes BTW are designed to minimize space charge effect.

The space charge is thus an excess of electrons near the plate. This has the effect of reducing the tube's ability to conduct and makes it harder to completely saturate.

In practice, the result is that the tube will not hard-clip like a transistor will. This means that a tube amplifier will have a clipping characteristic that can be quite 'soft' if just barely clipping; the amp will enter saturation in a gradual or perhaps even graceful manner, with less of the odd ordered harmonics that are caused when clipping onset is immediate as in transistors.

Because some odd orders and in general higher ordered harmonics are present, which the ear uses as loudness cues, the amp will just tend to sound louder at this point, but without breakup that accompanies hard clipping.

But even with hard clipping, tube amps do not make as much odd ordered harmonic distortion due to the space charge in the power tubes. The result is they sound smoother to the human ear.

This is why guitar players tend to prefer tube guitar amps BTW.

So the bottom line is the reason tube amps often seem to operate with more power than they should has everything to do with how they overload; specifically the reduced amount of odd orders present at clipping. If you get rid of this 'soft clipping' characteristic you often need a lot more power to seem to do the same job. Makes sense now?
^ I would agree that the softer clipping of tubes might make the sound of tube amps seem louder than comparably powerful ss amps, but as tube Watts often cost more than ss Watts, one might be able to buy extra ss Watts for the same money to compensate for the clipping issue, and perhaps more readily dismiss it altogether. Perhaps it might be wiser to compare amps on the basis of cost rather than Watts? Of course, that is not to say one shouldn't consider power output ability when purchasing appropriate amplification.
Is this "...excess of electrons near the plate." consistent and/or linear?
Sorry but, I'm not sure that "This is why guitar players tend to prefer tube guitar amps BTW." is necessarily true. Creating sounds is quite a bit different than replicating them.

Interesting thread, and think this comment by Atmasphere is very significant,
Because some odd orders and in general higher ordered harmonics are present, which the ear uses as loudness cues, the amp will just tend to sound louder at this point, but without breakup that accompanies hard clipping.
as I have read many times that the distortion created by the soft, gradual clipping of a tube amp is perceived by the human ear as an increase in loudness, therefore thinking tube amp watts are more powerful.

As far as guitar amps, I have read that there can be a difference in the design of the volume control circuit between tube and solid state. A solid state amp will reach maximum output with it's VC at very close to fully clockwise to avoid hard clipping, while a tube amp will reach maximum with the VC at only 3/4 of the rotation. This allows adjustment for varying amounts of that desired distortion in a tube amp.
Best to avoid clipping totally, however # watts it takes.

As long as its done well.....
I answer to jmcgrogan2's question and to follow up on Drussheaxe's response:
Current US law dictates that:
mercantile products (cotton) are weighed in Avoirdupois ounces
physical bullion (gold) are weighed in Troy ounces.
Avoirdupois ounce = 28.349 grams
Troy ounce = 31.10 grams
Avoirdupois pound = 16 Avoirdupois ounces
Troy pound = 12 Troy ounces
Avoirdupois pound = 453.504 Avoirdupois grams
Troy pound = 373.2 grams
10 pounds of cotton = 4.53584 Kilograms
10 pounds of gold = 3.732 Kilograms
I've owned many tube amps during my 45 years as a musician, sound technician, stunningly handsome bon vivant, and amazingly interesting gasbag. There is not only an appealing tone with tube guitar amps, but a tactile quality that experienced guitar players understand and is sometimes described as "snappiness" or "finger response" or other things I can't remember (I'm old...so SUE ME)...I have also owned a highly regarded (for its time) SS amp, and used it for a while until realizing it sucked. I just bought a cute little Class D Ampeg bass amp that sounds fine, so exceptions are made..."Modeling Amps" also are somewhat popular here and there, but I don't like them. None of this may matter, but I like to take any opportunity to talk about myself hoping that people will like me.
^Don't know enough about you to decide whether or not I like you, but I do like your sense of humor!
I don't typically care if I'm liked. Good thing, or otherwise I'd be terribly disappointed.
Drusstheaxe, please accept my apology for previously misspelling your username.
Well, my 200wpc SET amp sounds like it could easily blow down the walls of my listening room, sounding quite a bit more powerful than the 500wpc SS amp it replaced. More musical, too...
"...200wpc SET amp..."? What amp might that be?
03-17-14: Unsound
I answer to jmcgrogan2's question and to follow up on Drussheaxe's response:
Current US law dictates that:
mercantile products (cotton) are weighed in Avoirdupois ounces
physical bullion (gold) are weighed in Troy ounces.
Avoirdupois ounce = 28.349 grams
Troy ounce = 31.10 grams
Avoirdupois pound = 16 Avoirdupois ounces
Troy pound = 12 Troy ounces
Avoirdupois pound = 453.504 Avoirdupois grams
Troy pound = 373.2 grams
10 pounds of cotton = 4.53584 Kilograms
10 pounds of gold = 3.732 Kilograms

Thank you very much for that clarification Unsound. You are a gentleman and a scholar! Now, after all these posts we still don't seem to have a quantitative answer to the OP's original question. How many SS watts is 35 tube watts equal to??

Al, Ralph......we are all waiting. Try to be as accurate as Unsound was please. ;^)
1 tube watt = 1 SS watt.

Disclaimer: Your clipping mileage may vary....
^Thank you, but I'm not deserving of it.
A true scholar would have noticed That "I..." should have been "In...", and there is no such thing as "...Avoirdupois grams...".
03-17-14: Unsound
"...200wpc SET amp..."? What amp might that be?

This one (there's another like it for the right channel):

The Midlife Crisis
Al, Ralph......we are all waiting. Try to be as accurate as Unsound was please. ;^)

If we actually graphed the amplifier's distortion response when subjected to a standardized non-repetitive waveform, we could probably put numbers to that. Until then its a subjective experiment.

I can tell you this- if distortion is present it can cause the sound to seem considerably louder than one might expect. So given two amps, one lacking distortion and the other with distortion, the more distorted one is likely to sound considerably louder.

You know how SETs, when reviewed, frequently have the comment (paraphrasing):'...this amp sounded considerably more dynamic than it had any business being on account of its low power...' ?

This is entirely due to the distortion of the amp, which is unmeasurable at lower power levels. But if the power goes over about 20-25% of full power, the higher ordered harmonics come into play, which are likely only on the transients of the music. So you have the loudness cues on the transients and considerably lower distortion in between- the result will be that the amp sounds really dynamic. But its actually an interaction between how we perceive sound and the behavior of the electronics.

So to answer the question, I would say it depends on the amp and to no small degree the load (which must be benign). But the tube amps may seem to have anywhere from a 3 to 6 db advantage over transistor amps (of the same power) in this regard, depending on the topology of the amp.

I can break that down further- SETs will be more likely to seem to behave as if they have a lot more power, followed by push-pull triode amps. On the other end of the scale, a push-pull pentode amp employing feedback will seem to have the least 'overhead' in this regard, as they will have a sharper clipping onset.

The better tube amps will often seem to compress slightly before outright clipping occurs. This has a lot to do with improved power supplies, as a robust supply will reduce IMD in the amp.
Here they are in action, BTW.

Hot Hot Hot

.
Ait, I'm not sure why exactly, but I have to admit I'm impressed. Were those amps custom made, special order, or available off the shelf?
Atmasphere, am I to understand that you're suggesting that as long as an amp avoids actual clipping that it will sound more powerful the more it distorts?
Unsound,

I made them myself. Here's the build thread from DIYAudio:

Midlife Crisis

.
^Dang!
Thanks Al. I missed the focus of your original post; grabbed a piece without context.

Any idea why so few speaker designers don't do much about driver impedance compensation these days?

I've always been impressed by Jim Thiel's designs in this regard.
http://www.stereophile.com/content/thiel-cs16-loudspeaker-measurements
http://www.stereophile.com/content/thiel-cs24-loudspeaker-measurements

I recall many years ago that the Thiel website had an image of one of their crossovers. It was loaded with gobs of components which was puzzling to me since I thought first order filters required few parts.
Bop Reynolds, look at these pre coincidental driver Thiel impedance plots:
http://www.stereophile.com/content/thiel-cs2-loudspeaker-measurements
http://www.stereophile.com/content/thiel-cs35-loudspeaker-measurements
http://www.stereophile.com/content/thiel-cs12-loudspeaker-november-1989-measurements
I don't actually want to be liked, I was joking.
Atmasphere, am I to understand that you're suggesting that as long as an amp avoids actual clipping that it will sound more powerful the more it distorts?

Yes, to a certain degree. It will sound **louder** more specifically.

This distortion thing can be a big deal. To give you an example, we try hard to make sure our amps don't make much in the way of higher ordered harmonics (even orders are canceled not just in the load but in each stage of the amp, and with only one stage of gain, triode operation etc., odd orders are minimized). What we find is that a person that might have a 7 watt SET will turn the volume down before the amp is outright clipping "because it was loud enough', whereas the same customer using our 60-watt amp will drive the amp to nearly full power on the same speaker.

We've actually had customers call up and ask us why the amp does not seem to make any power; that changes if they actually bring a sound pressure meter into the room and see how loud they are playing.

IOW, tube amps make 'loudness cues' that interact with the human ear/brain system in a way that transistor amps do not. IOW its all about distortion.

IMO/IME experience you do indeed want the amp to be as undistorted as possible and lacking colorations (the ear interprets lower ordered harmonics, the 2nd, 3rd and 4th as 'lushness', 'warmth', etc.) because its all about the amp being part of musical reproduction rather than musical generation, if you get my drift. Doing that is a bit of a trick! If you add loop feedback to reduce distortion, you will actually add odd ordered harmonics (to which the ear is quite sensitive, and also finds to be irritating). Norman Crowhurst described this in his writings a good 50 years ago; not much progress has been made in that area since. That is why we avoid feedback when we can. But then you pay a different price for that, see
http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php