Balanced Low Power Tube Monoblocks?

Almarg, No, I don't seem to agree. The issue is that tube amplifiers are not always going to act like a true voltage source (that is the domain of transistors). You *can* get tubes to *start* to behave like a voltage source if you add enough feedback, but then IMO/IME, by doing so you obviate the main reason to go with tubes, which is linearity without feedback.

The problem with feedback is that it will *increase* the odd-ordered harmonics that the human ear uses to determine the volume of a sound. Since these harmonics are considerably higher in frequency (5th, 7th and 9th harmonics specifically) they also add an electronic brightness that everyone on this forum is very familiar with. Nelson Pass wrote a great article about this:

http://www.passlabs.com/pdf/articles/distortion_and_feedback.pdf

pay particular attention to the graph showing the odd orders.

So IOW we as audiophiles are always having to decide between sound that might not be perfectly flat but otherwise sounds natural *or* sound that measures flat but sounds hard and bright! Either way there is a coloration and either way neither one sounds like the frequency response is flat.

I for one prefer highs that are natural as opposed to bright. I don't like boomy bass or anemic bass either, so I choose speakers wherein the designer knew that the amplifier driving that speaker was not going to be a perfect 'voltage source'. see

http://www.atma-sphere.com/papers/paradigm_paper2.html

for what that is all about.

Ralph -- Thanks very much for your good response, with which I am in complete agreement.

But please note that my post (the one dated Sept. 8) was not dealing with tube amplifiers, or with amplifiers or speakers designed based on the power paradigm. It was addressing the narrow situation in which a speaker having a low impedance in the bass (e.g., 4 ohms), and a higher impedance in the mids and treble (e.g. 8 ohms), is being driven by an amplifier (typically a solid state amplifier) having an output impedance which is negligibly small in relation to the speaker impedance at any frequency.

And the question was whether or not such an amplifier driving such a speaker would produce an excessively bright response as a consequence of the amplifier not being able to double power into 4 ohms (relative to 8 ohms). And my contention is that it will not, as long as the volume levels are such that the amplifier is not called upon to deliver more current than it is capable of (and as long as the amp does not produce an excessively bright sound for other reasons).

Best,
-- Al

Shop around for a used Rocket-88R.

Thanks for the suggestions, Al.

Almarg- OK, I see your point, but in practice such an amplifier will in fact 'produce an excessively bright response' not due to frequency response variation but due to generation of odd-ordered harmonics.

I apologize for repeating myself often, but the simple fact is that that audio industry is ignoring 45 years of research into how humans perceive sound! Were that research taken into account, I would agree that your statement is correct as today's amplifiers would be different. What amazes me about all this is how the audio industry has stuck steadfastly to design rules that, even while they were being implemented during the 1960s, were already being proven wrong by said research.

What I am talking about is the typical amplifier that you are describing violates the most fundamental rule of how we perceive volume, by exaggerating odd-ordered harmonics. Another way of putting this is that you can be convinced that a sound is a lot louder than it really is if the 5th, 7th and 9th harmonics are tampered with. These harmonics are not only cues to the human ear brain system, they also contribute to brightness- quite literally our ears are more sensitive to these harmonics than they are even to vocal frequencies! So there is almost no way an amplifier like that will not appear to have excessive highs.

This is the fundamental reason why tubes are still around after being declared 'obsolete'...