solid state vs tubes

I think Nelson Pass chose SS because he felt there were already alot of really good sounding tube amps, the trick was to get SS to sound good and he wanted to take on the challenge - don't know whether his stuff sounds tubelike or not, though he often describes the ways in which his circuits are similar to tubes in their simplicity compared with other SS designs. Mrtennis, I have no idea if there will ever be a time when you can detect the difference between SS and tubes, too subjective (yours) to know, but it does seem that there are at least some audiophiles that would be hard pressed to detect the difference and know which was which.

Thanks for the correction Mrtennis; However, what I was trying to say (among other things) is that unless the designer/engineer used the same specs, layout, parts, construction, wiring, grounding, etc. in designing the amps, it won't matter if they are solid state or tube, they will absolutely never sound the same. Apples to apples. Two different 50 WPC tube amps will never sound the same unless they are the same amps. Same for solid state equipment. You will always detect a difference in sound from different equipment, even if they have the same specs. The transfer functions (don't ask) of each piece of equipment are totally differnt. That means that gain, phase, etc. are different based on the design and circuitry. That is what some designers tried to do in the past. Copy transfer function responses of high end equipment in the designs of their own. So, if we are talking about amps, and not pre-amps. First, what speakers are we considering? What is their impedance characteristics over frequency and power? Knowing that, what amps can handle that? If the speakers loads are very difficult, then only a few amps can handle them correctly without oscillating or blowing up. It totally depends on what the engineers intended in the design of the amps. Input impedance, sensitivity, gain, output impedance, load handling characteristics, power, voltage, phase, price, efficiency, etc. All of these must be taken into consideration in the design and as I mentioned earlier, depending on the price point, compromises must be made. So, the short answer is no. No tube amp will sound like a particular solid state amp or visa versa. Even two tube amps don't sound the same. It will ultimately come down to what type of sound you want. Real, altered, bright, fast, etc. This is why the used market is so great. There will always be the next greatest and better piece of equipment coming and someone will absolutely have to have it and will sell their other equipment to make room. I know a person that sold their Mark Levinson 20.6s because he doesn't have room for his top of the line Boulder amps and his Audio Research 610s. So, even though the 20.6's are better still than just about anything out their, they had to go and if I had the inclination, I would grab them. Solid state or not. That is not to say that their aren't any tube amps that are just as good or better, but you are now in the upper ranges of high end. you want great sound? take a listen to be top of the line Boulder amp/pre-amp. I haven't heard a tube set up better. Close or just as good? maybe, but better? I don't know. enjoy the music. Enjoy the race.

Minorl, not to put to fine a point on it but the idea of designing an amplifier to pass a signal without distortion is being heavily glossed over in your arguments, which, other than that, I find myself in agreement with.

The problem lies with the fact that our ears, regardless of the individual, use a set of common rules that govern our perceptions. Now really, that is not a problem except that the bench tests that are commonly used are for the most part not devised with these perceptual rules in mind. So as a result, a common experience is that an amplifier that measures well does not sound good, because **in the attempt to measure well, the human perceptual rules are being violated**.

So it is not true to say that the amplifier that has the 'lowest distortion' will be in fact the amplifier that actually *has* the lowest distortion; the two can be quite different! Often 'higher distortion' amplifiers (as measured on the bench) are lower distortion when subject to the reality of our ears.

In short, the bench measurements come off as an example of the Emperor's New Clothes. Our ears OTOH, are the real thing. Now it is a simple fact that tubes more closely obey these perceptual rules than transistors do, that is why it is so hard to find the transistor amps that really sound like music. However, and I point to Nelsen Pass as an excellent example, when you find such an amplifier it will be because the designer is also looking at how our ears work.

Atmasphere,

Does what you say about loudness cues, our ears and how amps are designed apply mainly in regards to how amps distort?

Loudness cues conveyed by certain harmonics is a natural occurence, correct? What if say a SS amp conveys these cues accurately as they would be if heard live? That may not be as pleasant as them not being conveyed accurately say as a result of tube amplification, but that does not make it wrong, does it? If not clipping/distorting, what if a good amp just conveys what's there accurately, and measurements support that this is what is occurring?

If an amp is not clipping and is fast enough to deliver transient peaks accurately, some might perceive that as a good thing I would think rather than relying on the amp to filter or transform the sound in a manner that makes it more pleasant or digestible. That does not occur when listening to things live. The sound and the harmonics that comprise it are delivered without benefit of amplification or filtering devices to shape it into something more digestible to our ears, for better or for worse.

Mapman- I won't speak for Ralph but I think you are missing something important here. We are not talking about an amp that is filtering or transforming anything. The issue here is that, supposedly, we perceive certain kinds of distortion (can't remember if its odd or even harmonics) as more harsh or objectionable than others. So, (to make up an example) 0.10% distortion of those harmonics sounds "worse/louder" than 1% distortion of those to which our "ears" (actually brains, I think) are less sensitive. Remember the numbers are made up and I also believe that even within the odd vs. even harmonic dichotomy, there are certain specific harmonics to which our ears are more sensitive.

I only say "supposedly" because I don't have any independent knowledge of the science nor am I an auditory physiologist or experimental psychologist. However, this explanation is consistent with what I remember from my long ago undergrad days about differential response to various kinds of stimuli. This also jibes with what I have heard w my own ears; that ss amps that measure 1X% THD do not, in many cases, sound as good as tube amps that measure 10X% THD.

If your hypothesis is that minimizing THD is an important design goal for an audio amplifier, then many would say that, based on their listening tests, your hypothesis cannot be experimentally verified. That statement does not deny that minimizing distortion is not an important design goal, just that minimizing THD (which is measured in a very specific way) cannot be shown to be an important design goal.

Another way to think of this is that it may be a case of "if your measurements don't match up your experience, maybe you're measuring the wrong thing." In this case, measuring THD may not be the right thing. I think Ralph would suggest a weighted measurement that assigns the most "weight" to those harmonics to which we are most sensitive. Call it WHD (Weighted harmonic distortion) or what have you. The relative weight assigned to each harmonic would have to be determined experimentally, in order for this concept to be applied in practice. When you think about it, THD is actually a specific type of WHD, in which the weight is "1" for each harmonic.

I'll stop now before I dig myself in too deep.