Tube vs Solid State Is the War

[Orb]

Disagree in theory here, the waveform shape each of these attacks and overtones and harmonics takes when they wiggle the microphone is, wait for it..."sinewave" ish... (not a textbook perfect sinewave, but damn near). No worries, it took me a while to grasp the concept and reading up on acoustics till my ears blead. ha ah ha.

Also, the amp can only be at one point at any one time, whether it is rising in output or dropping, and I do agree that a multi tone burst is better than just plodding in one constant frequency sinewave, and, any twin tone (that is a simple tone burst for sure) intermod test will reveal differences between amps, but it is still the level of these differences that are of concern....dang it be all, our ears really do have a limit to what they can do, despite what folks seem to believe to the contrary.....

...now what our brains can do, well ! ! !

Tom

Hmm I take it a different way from reading various books and papers.
If you look at a complex waveform in both time domain and frequency domain it does not look like a normal tone type sinewave, let alone using fourier analysis to provide snapshot of the fundamental and harmonics which will show how much different a single sinewave looks to a complex wave that must be derived from multiple sinewaves to be generate the original waveform.
In reality you would need a hell of a lot of sinewaves to make up a complex waveform such as an instrument playing a single note.
There are various papers on this subject discussing in terms of physics musical instruments and the waveform, including discussing sinewaves-tones-fourier with that of the instrument.
Using just the amplitude against time it may look that way, but it does not give the complete picture.
As an example here is microphone measurement of various instruments, using this not because it is more about energy above 20khz, but it shows just how complex a single note is,, especially when one considers how much it fluctuates from 20hz-20khz and also in the time domain due to attack-sustain-decay (which is not shown with this study):
The 2nd chart is interesting for the various amplitudes of the harmonics.
http://www.cco.caltech.edu/~boyk/spectra/spectra.htm
Which is an fft (single snapshot is the way I look at it) derived from a point in the amplitude-time graph.
That is a fair amount of sinewaves.

The problem is, there are not really that many well recorded-measured instruments out there that can be used as a reference.
To see what it really looks like you need to take the fundamental and all the harmonics, then correlate them to an envelope-spectral decay type graph where amplitude is vertical, frequency (which increases for each harmonic) is depth, and horizontal is the time.
I have only ever seen this done a few time, but it does show interesting characteristics when it is.

Appreciate we differ on this and as neither of us are experts agree either of us could be wrong or even both partially right
Cheers
Orb

 

[Orb]

To throw a bit more into the fire, why Bob Carver believes tubes are "nicer", from a recent interview:


So there you are, it's all very simple really ...

Frank

He mentions part of it relates to sound bouncing off the walls, so what happens for those with large rooms, especially if focusing more on the midrange instead of the extreme high and low frequencies?
Would the conclusion then be the size of the room dictates how pleasant the tube sounds due to soundwave reflection as suggest in the quote?

Also, what about solid state amps with output impedance that match tubes (there are quite a few around), is it to say these are equally pleasant?

Cheers
Orb

 

[Orb]

........The corollary question also must be posed: how can I be sure that your conclusion that a particular SS and tube amp are indistinguishable is factual and not simply a matter of opinion?

Science shows that timbre, identifying instruments, etc can be correlated to the instrument's harmonics and more recent study from what I have read imply the time domain is also critical.
So we remove listeners from the equation but acknowledge that we need to measure a complex soundwave outputted by the source (for baseline reference), and then pre and then power amp and investigate said waveform as I suggested before.
A listener is not required as it can be done with measurements, later on a model is required to try and understand (if there are differences) how this may reflect the output to a listener in terms of timbre changes-richness-etc that are associated with tubes as being good.
This also bypasses output impedance challenges.

Not sure why we even need to involve listeners at this stage when comparing solid state with negative feedback to say a tube, where both measure well.

Thanks
Orb

 

[Phelonious Ponk]

To throw a bit more into the fire, why Bob Carver believes tubes are "nicer", from a recent interview:

What happens in a vacuum-tube amplifier, the amplifier makes another sound that is related to the sound it heard. In other words, the amplifier is able to listen to the room. Because it’s hearing reverberation, echoes, time delays, all of the components associated with the venue. The loudspeaker speaks, and the room speaks back to the loudspeaker. The amplifier hears it, via the signal going back around the feedback loop, and out it comes again. It’s not delayed by much; the real decay is the acoustic delay. That delay makes it sound spacious and big to our ear-brain system. We love sounds that have ambience, and echoes, and stuff like that.

The output impedance of a solid-state amplifier is so low that when it tells the speaker to move, the speaker sends the wave out, it bounces off the walls, comes back, and the solid-state speaker will not allow the speaker to move in response to the sound wave coming back and hitting it. The amplifier shorts the speaker out so that the speaker can’t move on the back wave. The amplifier is said to have a very low output impedance. It shorts the speaker out, basically.

A higher output impedance is one of the things we hear when we listen to vacuum-tube amplifiers. It’s one of the things that makes a vacuum-tube amplifier sound so enjoyable and so nice and so spacious.

Oh my....amplifiers listening to rooms, poor driver control as reverb, good damping "shorting out" speakers, high amplifier output impedance as a virtue...Bob has, evidently, watched the price of voodoo soar into the atmosphere while the high-end pushed anything too good a value into the "midfi" bin, including Carver amps.

So sad. It reminds me of when a great R&B singer named Rod Stewart saw the money, donned a scarf and a pair of spandex pants and became a disco queen.

Tim

 

[microstrip]

To throw a bit more into the fire, why Bob Carver believes tubes are "nicer", from a recent interview:
"
What happens in a vacuum-tube amplifier, the amplifier makes another sound that is related to the sound it heard. In other words, the amplifier is able to listen to the room. Because it’s hearing reverberation, echoes, time delays, all of the components associated with the venue. The loudspeaker speaks, and the room speaks back to the loudspeaker. The amplifier hears it, via the signal going back around the feedback loop, and out it comes again. It’s not delayed by much; the real decay is the acoustic delay. That delay makes it sound spacious and big to our ear-brain system. We love sounds that have ambience, and echoes, and stuff like that.

The output impedance of a solid-state amplifier is so low that when it tells the speaker to move, the speaker sends the wave out, it bounces off the walls, comes back, and the solid-state speaker will not allow the speaker to move in response to the sound wave coming back and hitting it. The amplifier shorts the speaker out so that the speaker can’t move on the back wave. The amplifier is said to have a very low output impedance. It shorts the speaker out, basically.

A higher output impedance is one of the things we hear when we listen to vacuum-tube amplifiers. It’s one of the things that makes a vacuum-tube amplifier sound so enjoyable and so nice and so spacious. "

So there you are, it's all very simple really ...

Frank

This recurring argument about the feedback and output resistance effects has been shown not to explain the good sound of tube amplifiers. If you take a transistor amplifier and connect a resistor in series with the output, before the feedback point, you do not get a tube amplifier sound. Also if you use an electrostatic loudspeaker, known to have a very low EMF, the differences still exist.

Anyway if this was true, it would be very easy to measure - and current measurements of amplifiers, as far as I know, do not depend on room acoustics.

 

[JackD201]

The answers are right in front of us even if they aren't quite clearly understood just yet. SS amps that have tubelike qualities are fast switching, highly biased or both. Tube amps with SS qualities are those that can deliver current similarly. Have they met in the middle as far as SOTA examples of both go? In my opinion and limited experience, no, not quite yet.

From a physiological standpoint there is reason to believe that despite human's limited hearing response, switching should be detectable. Lot's of hearing sensitivity studies from top medical universities studying inner ear hair cells suggest it is very likely.

 

[Phelonious Ponk]

Lot's of hearing sensitivity studies from top medical universities studying inner ear hair cells suggest it is very likely.

I dunno, Jack. If it were about the hair in our ears no humans would hear as well as old men. And the opposite seems to be true.

Tim

 

[JackD201]

Wahahahahaha! Good one!

 

[Gregadd]

Oh my....amplifiers listening to rooms, poor driver control as reverb, good damping "shorting out" speakers, high amplifier output impedance as a virtue...Bob has, evidently, watched the price of voodoo soar into the atmosphere while the high-end pushed anything too good a value into the "midfi" bin, including Carver amps.

So sad. It reminds me of when a great R&B singer named Rod Stewart saw the money, donned a scarf and a pair of spandex pants and became a disco queen.

Tim

If there was a PT Barnum of Audio, Bob Carver would be first choice. Carver knows it does not matter to make a good product if no one knows about it.

 

[Stereoeditor]

The null hypothesis is different from the null test.

Here what JA had to say;
Quote:
Where is that original modified Carver amp today?

Bob Carver took it back with him when the Challenge was over, where it was used as the prototype for the M1.0t amplifier that was released in 1986. Stereophile reviewed this model in April 1987 (review not yet posted in our archives) and found that it neither measured nor sounded like the C-J tube amp of which it was supposed to be a clone. The null I measured between the production M1.0t and the tube amp using the same methodology as Bob Carver was just 36dB and then only in the midrange.

John Atkinson
Editor, Stereophile

OK, fair enough, I can't remember all these things these days...but, there is no argument, he made an inexpensive solid state amp sound indistinguishable from a "high end" tube amp. And they acknowledged it. That is the fact I put forth. They preferred the sound of that tube amp and, at the time, Bob duplicated it. They had better ears then than now, lord knows what kind of authority they are on the sound of anything these days...

The situation with the Carver Stereophile Challenges is complicated. The original challenge in 1985 (before I joined the magazine) involved blind testing the prototype Carver amplifier against a pair of Conrad-Johnson monoblocks on just the treble and midrange panels of Infinity RS1B loudspeakers. (The Infinity speakers used powered woofers.) The report on this Challenge can be found at http://www.stereophile.com/content/carver-challenge . And yes, it did appear that the final version of the Carver amplifier sounded like the C-Js - but only in the midrange and above.

For the rematch at the beginning of 1987, I insisted that the amplifiers be compared full-range, using Celestion SL600 speakers. I measured the null as mentioned above with the amplifiers driving these speakers, and the maximum null was indeed just 36dB and then only in the midrange. Bob Carver subsequently said in an interview - see http://www.stereophile.com/content/bob-carver-carving-name-himself-page-3 - that 36dB was certainly not enough to guarantee that the amplifiers would be indistinguishable. We did a series of blind tests at that time and Bob Carver agreed that J. Gordon Holt _could_ distinguish the amplifiers by ear, contrary to what you say. I did take part in these tests, but when it came time to score my tests, Bob Carver couldn't remember what amplifier I had been listening to in each trial.

This was all reported in the April 1987 issue of Stereophile - that article will be posted in our on-line archives next year, 25 years after the event.

One thing that came out of the 1987 Challenge was that halfway through the tests, Bob hooked a long length of narrow-gauge wire in series with the Carver amplifier's output to increase its source impedance to better match that of the Conrad-Johnson. This was something he subsequently incorporated in production, to the best of my knowledge.

John Atkinson
Editor, Stereophile

 

[Phelonious Ponk]

I would expect one to be able to distinguish the bass content of a Carver SS amp from a Conrad-Johnson tube unit. I would expect the control of the Carver to be audibly better. Whether or not that would be preferably better is a matter of personal taste, of course.

Tim

 

[Gregadd]

Is the failure of two people to identify an amp under DBT proof of something? I will hold you guys to your answer.

BTW I owned the CJ MV50 and PV5 at that time.

 

[Phelonious Ponk]

Is the failure of two people to identify an amp under DBT proof of something? I will hold you guys to your answer.

Yep. It proves that those two guys couldn't tell the difference that time.

Tim

 

[Gregadd]

Yep. It proves that those two guys couldn't tell the difference that time.

Tim

It also proves, contrary to popular opinion, they were not afraid of DBT or to publish results contrary to previously held beliefs.

 

[Phelonious Ponk]

Yes, it was rather remarkable.....were there threats of lawsuits in the background that we never knew about? Just wondering....it does seem remarkalbe, and apparently easily forgotten and needs re-learning once in a while....

Tom

Honestly? I don't think either of them thought Carver would ever pull it off. I don't think it was courage. I think it was confidence.

Tim

 

[Gregadd]

OK, but lets be sure what we think we got a hold of!

I see that this test proved that there was no magic involved in tubes nor solid state, and that by manipulating phase, frequency and distortion they both sounded so similar to esteemed audiophiles that they could not tell the difference................again, it proved that tubes or solid state, neither one is magical, it IS all in the execution and circuitry.

Please don't overlook this.....between solid state and tubes, there is no MAGIC, only execution (and goes without saying expectation bias and preference and blah
blah..

Tom

Nothing to pin down there.

Inadvertently BOB showed that there was such a big difference in tubes and solid state that it took his considerable skills to make them sound the same http://www.whatsbestforum.com/showthread.php?3909-On-proving-the-negative

Logically he then skirted the question of which was best. Imitation is the sincerest form of flattery.

 

[fas42]

Frank, in post 108 you quoted Bobby Carver, where pray tell did that information originate and can I obtain it somehow?

Tom

Possibly in a number of places, but I found it here: http://stoneturntable.net/blog/?id=5367348772525899009

BTW ...

again, it proved that tubes or solid state, neither one is magical, it IS all in the execution and circuitry.

Please don't overlook this.....between solid state and tubes, there is no MAGIC, only execution

Couldn't have put it better myself, Tom ...

Frank

 

[fas42]

Orb, while I agree there is energy above our abilty to hear in instruments, these energies occur as sinewaveish ( I make a careful but technical distinction from a pure sinewave as extracted from the movement of a circle...wikpedia has info on that), but again, the waves, all of them are damn near a sinewave. Air does not conduct square waves or triangular waves or any other stuff. This has to be understood, and thus I am not partially wrong on this matter of sinewaves (sinewavish...they are not perfect circle waves but so very very close). Think of air like water, if it helps...a push immediatly entows a pull so to speak. Even if you smack water with a big flat stick, it does not project out with a repeating square wave form. Its nature and all that jazz. Now, making a square wave out of an infinite number of sinewaves is good math stuff. But, folks can get confused about electronics easily, especially when it comes to filters, who generate sinewaves at the frequency they are excited at, even if they are excited by pules and not sinewaves, its the old push the swing thing.

Tom

In the excellent electronics "bible", The Art of Electronics, the authors talk of the signal being a "wiggle", and when you look at an audio signal that's exactly what is: no matter how much you zoom down into it, to the limit of the bandwidth and the effective bit depth of the signal that's all it ever is, just a very pleasant, meandering wiggling. Looking at a particular bit as a speaker driver would, it doesn't look dangerous or difficult to handle at all, just like going for an interesting hike in the country ...

On a side note, this thing about high res having extra information at higher frequencies is a real furphy, or red herring. Looking at the signal as a wiggle you can certainly see this very high freq wiggling above 20kHz taking place. But it is completely random, at a very low level, like moving your shoe slightly to the left of right each time you put it down as you go for a walk. In other words, it is information that is completely meaningless, of zero value, in the bigger picture of what's taking place.

Frank

 

[fas42]

SS amps that have tubelike qualities are fast switching, highly biased or both.

From a physiological standpoint there is reason to believe that despite human's limited hearing response, switching should be detectable. Lot's of hearing sensitivity studies from top medical universities studying inner ear hair cells suggest it is very likely.

Jack, you've got me on this one! Are you talking about class D, or reducing crossover distortion, or what?

Frank

 

[JackD201]

So it's not the size of the wiggle that counts ey?

No not class D, all transistors switch, at least that's how I understand it. As far as the sensitivity studies go, the cone like "composite" construction of the inner ear (as opposed to Tim's outer ear hair ) hair cells suggest that while the frequency might not register in the brain sound pressure does. In other words we are much more sensitive to minute changes in volume than previously thought. If this is the case, then MY guess is, the cumulative effect of these zero crossings could be the root of the SS "grainy character" cliche. Come to think of it, SS designers have actually been trying smooth the transition since the beginning. Companies like Spectral, Soulution and Lamm have attacked it by switching faster, companies like Pass Labs by going into fewer output devices with heavy class A bias. ML is dealing with it by interleaving. In the past it was done mainly with an intelligent bias system. Edge has it's own proprietary biasing scheme. Think about it for a minute. The dig against SS is that it does not have the "flow" of tubes. This is something I agree with even if I am using SS output stage amps that are already fast switching AND are biased fully in Class A. The study stated in passing that 24 or 30 frames per second might be enough to fool the eyes but the ear evolved to detect over 20,000 frames per second so they, in some instances, could be harder to fool. Interesting stuff. Where the heck is that study? I will try and find it again.

If we look at things from the zero crossing point perspective the same problem appears to be the very same as a digital vs analog debate or Hi-Rez vs Redbook debate even. Orb already mentioned the time domain, I think he's right.