How important is the efficiency of a speaker to you?

@rauliruegas   I suggest since you are such a big fan of the Parasound JC1+'s sound that you go out and immediately buy a pair, if you haven't already...That's what I am talking about...;0)

Dear @daveyf  : I know and listened sevral times in different home top room/systems the original JC 1 and the JC 1+ too.

But, I don't need to buy it because my Levinson 20.6 monoblocks was and till today it's the J.Curl Statement Design. Yes better than the JC 1+ and better that many today $$$$ SS monobloks and guess what: the 20,6 are pure Class A and doubles its power down to 0.5 ohms. It's a true beauty of design and it's a learning electronics for any SS amps designers.

That's what I'm talking about.

R.

@rauliruegas   Presumably by now you have replaced the caps in those ML 20.6's?? Yes?

 I suggest since you are such a big fan of the Parasound JC1+'s sound that you go out and immediately buy a pair, if you haven't already...That's what I am talking about...;0)

@daveyf :)

Distortion vs frequency is a better measure of how musical the amp might be. It must not rise in the audio band else higher ordered harmonics can become more audible than THD values (usually measured at a pretty low frequency) would suggest. You can see this is a problem with the JC1. This is caused by a low Gain Bandwidth Product value, where the feedback ceases to be supported at a certain frequency and so decreases, initially at 6dB/octave. Distortion thus rises on a complementary curve. This is a very important reason why do many solid state amps of the past have sounded bright and harsh- its literally what has kept tubes in business the last 6 decades.

Dear @daveyf   .: You are rigth and I was lucky enough to found out all the power supply, protection circuit, input electrical circuit electrolithics at its original values through the best of the best caps: Vishay.

When I did it ( less than 2 years ago ) and I listened again what I listened was and is nothing less than stunnig for say the least. I bougth my 20.6 second hand and I did it to been paired with a pair of 20.5s that I owned too in a bi-amp configuration and latter on that I learned I sold the 20.5s

" The amplifier performed beautifully, showing maximum distortion of 0.42% THD + N at 20 kHz. This distortion level would not be audible on music and is comparable to published ratings for high - quality tube amps driving standard loads; here, we were using one-fourth of the amplifier's minimum rated load! "

 but in that 20's monoblocks review ( not the 20.6 that are even better ) that  THD does noit changes even at 1 ohm where the 20's  shoiwed 800 watts. Even those reviewers made this experiment with the monobloks:

"" An enthusiastic reviewer might call a beefy amplifier an "arc welder" as an exaggerated compliment to its ruggedness and current -handling capacity. However, no one would really expect an amplifier to actually melt steel. Almost no one, that is, except this reviewing team. We say this amplifier is an arc welder and back up this statement with a photograph (Fig. B1) of two 0.05 -inch steel plates welded together by a pair of Mark Levinson No. 20s. Arc welding is accomplished by creating an electric arc that melts metal. The molten sections of the items to be joined flow together and are then allowed to cool. In practice, the power source is connected to the two pieces to be joined and to a flux - coated welding rod. The arc is struck by momentarily shorting the rod to the work pieces. The flux is vaporized, forming an ionic conducting path for the arc and cleaning the metal. The arc stabilizes at about 100 amperes and 30 V (creating temperatures of 3,000° F), depending on the thickness of the metal and welding rod. If this sounds like the world's worst amplifier load, you're right! Coauthor Clark summoned Paul Grzebik to carry out the task. Paul has the reputation, in Detroit's technical community, for a willingness to try anything once, from building a parade float to scaling a TV transmitting tower. He readily agreed to our assignment. Clark drove both No. 20 amps with a 1 -kHz square wave to full output into a series resistor mixing network that combined both amplifier Fig. B1-Results of the arc -welding experiment. outputs in parallel to obtain the high current needed. After experimentation (and several blown line fuses), approximately 1 ohm was found to deliver the maximum current for starting and sustaining the arc. Wearing a mask and gloves (the intense blue light from the arc can burn the unprotected retina, while molten metal can splatter on the hands), Grzebik began welding. The arc turned out to be a fairly effective plasma tweeter, creating strong 1 - kHz square -wave sound radiation that required wearing ear protectors as well. Grzebik completed a small weld and, impressed, pronounced it satisfactory. After the welding, the No. 20s, still only lukewarm, were again put on the test bench. Distortion tests verified that no change in their performance had resulted from this extraordinary exercise. What's the point? With this test, Clark verified his confidence in the exceptional output capability and comprehensive protection built into these amplifiers. A few other amps might be able to weld steel without destroying themselves, but the No. 20s were certain to survive the experiment. One note: Don't attempt this feat yourself unless you are an accomplished welder, have the proper equipment, and are using amplifiers with extraordinary protection circuitry and output stages that can handle current extremes. Injury to yourself and destruction of lesser amplifiers may result. Don't expect manufacturers to repair your damaged amp under warranty, either! "

So,  we don't have to care on what  that tube manufacturer posted because it does not happens exactly as that. The very old 20's proved that and that design comes from 1986.

As always, there are designers and designers and J.Curl is really good . Remember the Vendetta Research phono stage? came from J.Curl and several other electronics designs as the Parasound and the like.

R.