Richard Clark $10,000 Amplifier Challenge - Why Couldn't Anyone Pass this Test??

Wow, what a great post from Ralph/atmasphere. As always!

+1.

Also, while it doesn’t directly affect anything that was said in Ralph’s excellent post, to be precise I would just add that Ohm’s Law and the stated definition of power apply to resistive loads. And to the extent that a speaker’s impedance is partially capacitive or partially inductive at various frequencies the amount of current corresponding to a given power consumption by the speaker will differ somewhat from what Ohm’s Law would predict for a resistive load having the same impedance magnitude (i.e., the same number of ohms). In particular, impedance phase angles that are highly capacitive at some frequencies can increase current requirements to a significant degree, at those frequencies. But not by nearly as much as some manufacturer literature and some reviews might lead us to believe.

Best regards,
-- Al

Erik_Squires 5-15-2017

atmasphere:
I am saying your entire argument is bunk, because the ideal amplifier is a voltage source, not a current source.

I’ll have to disagree with you on this, Erik. The ideal amplifier is a voltage source if the speaker it is used with is designed to sound its best when driven by a voltage source. As Ralph indicated, many speakers are not designed that way. While some others (such as the Daedalus Ulysses I use) don’t particularly care about amplifier output impedance or voltage source behavior, as their own impedance is very flat. And of course many people get great results with tube amplifiers such as SETs that have output impedances similar to the output impedances of Ralph’s designs (e.g., 2 to 4 ohms or so for most models).

Also, as Ralph indicated the output impedances of his designs are not nearly high enough for them to be considered to be current sources.

Finally, as I said earlier in the thread, "the bottom line with respect to the tube-friendliness or lack thereof of the ESL57 is perhaps indicated by the fact that it was designed before solid state amps existed." Although admittedly my understanding is that many of the tube amps of that era did incorporate significant amounts of feedback, which in the case of those amplifiers brought them somewhat closer to behaving as voltage sources than many high quality modern tube designs.

Best regards,
-- Al

And as I mentioned, some speakers are deliberately hard to drive in the bass, or use smaller-dual woofers which put a strain on amplifiers. When I look at the impedance curves and read about reviewers talking about how "discerning" this speaker is, how easily it could tell the difference between a Boulder XYZ amp and their Onkyo receiver, well, duh. It was made that way.

But this discernment does not make either the amplifier or the speaker more musical. It’s just more demanding.

Yes, I am very much in agreement, Erik. As I and some others (including Shadorne) have said in other threads here, the musical resolution of a component or system, and its ability to resolve differences between components, cables, or tweaks, are two different things. And generally speaking the correlation between the two, while certainly not zero, will be a loose one.

My perception has been that many audiophiles fail to recognize that point, as evidenced by how quick some are to allege lack of resolution (referring to musical resolution) as being the reason others may not hear differences when performing comparisons between various hardware.

Regards,
-- Al

IMO it is a somewhat misleading oversimplification to categorize the ESL57 as being either an easy load or a difficult load.

It is a difficult load in the sense that its impedance descends to low values in the upper treble region, due to the capacitive nature of the impedance. Although even in that region its impedance is not nearly as low as the sub-1 ohm impedances of some other electrostatics, such as many of the Martin-Logan designs.

However, that difficulty is of course mitigated by the fact that most music contains relatively little energy in the top octave, where the impedance is particularly low.

It is an easy load in the sense that damping factor is a non-issue **with respect to bass control,** as Atmasphere indicated, because of its high impedance in the lower parts of the spectrum.

However, it will be a load that is **revealing** of amplifier differences, not only because of its transparency and musical resolution, but because differences in damping factor among different tube amps, and also between tube amps and solid state amps, will have tonal consequences.

Damping factor is inversely proportional to an amplifier's effective output impedance.  (I add the word "effective" to indicate that I am referring to output impedance taking into account the effects of whatever feedback may be present). The interaction of the amp's effective output impedance and the speaker's wide variations of impedance over the frequency range will certainly have tonal consequences, especially among different tube amps, and between tube amps and solid state amps. Less so among different solid state amps, since their effective output impedance is near zero in most cases.

In any event, the bottom line with respect to the tube-friendliness or lack thereof of the ESL57 is perhaps indicated by the fact that it was designed before solid state amps existed.

Regards,
-- Al