Balanced Low Power Tube Monoblocks?

Thanks, Joe. Now, for the 2A3 tube vetting...

Grant -- Best of luck with the new amps.

Some approaches to consider if you want to try to find VINTAGE 2A3's, aside from the usual dealers who will of course charge very high prices when and if they have any for sale:

1)Take out a subscription to Antique Radio Classified, and run a free want ad there each month.

2)They were used in the power amplifier/power supply chassis of several very high end multi-chassis "radios" ca. 1935. Most notably, those made by E. H. Scott (no relation to H. H. Scott, the hifi manufacturer who came later). During the intervening 75 years, the power amp/power supply chassis have often become separated from the rest of the set, and sometimes appear for sale in ARC or on-line auctions. I found one via a local classified ad for $35 some years ago, complete with 4 good 2A3's. There were undoubtedly a lot of people in your particular neck of the woods who owned these sets, and some may still be sitting in basements, or become available through local auctions, tag sales, classifieds, etc.

The particular Scott sets which used 2A3's were the Allwave 15 and the Allwave 23, also known as the Allwave Imperial or Allwave High Fidelity.

3)The Brook amplifiers of the early 1950's (designed by Lincoln Walsh) commonly used 2A3's (sometimes 300B's), although they appear infrequently and usually command high prices.

Regards,
-- Al

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.