The worst wine I ever had was a cabernet (merlot? no, cab...) from Steele. Very "green" tasting, in the sense of grassy. And, yes, I drank the entire glass. Why? To see how many flavor components I could pick out. (Not many.) But it was instructive.
The same is true of stereo. Listen to the good, the bad, and the ugly. (Clint's around here, somewhere.) It's a good way to learn how to contrast and compare. If you hear something "bad" try to find a schematic and see if you can figure out why it didn't do what it was supposed to do. Don't neglect the power supply/regulator design.
Balanced phono stages are quite possible, either by duplication of the RIAA filter on each phase or by using a 'flying' filter. It would be nice if cartridges had a mid-coil tap, though.
Nuvistors are/were nifty little critters, but ultimately a dead end in the practical sense. I don't think anyone is making any, so designing a circuit based on such a tube is not a long term solution. Where will you go for replacements when you need new ones?
Grey
The same is true of stereo. Listen to the good, the bad, and the ugly. (Clint's around here, somewhere.) It's a good way to learn how to contrast and compare. If you hear something "bad" try to find a schematic and see if you can figure out why it didn't do what it was supposed to do. Don't neglect the power supply/regulator design.
Balanced phono stages are quite possible, either by duplication of the RIAA filter on each phase or by using a 'flying' filter. It would be nice if cartridges had a mid-coil tap, though.
Nuvistors are/were nifty little critters, but ultimately a dead end in the practical sense. I don't think anyone is making any, so designing a circuit based on such a tube is not a long term solution. Where will you go for replacements when you need new ones?
Grey
I made the MOSFET power follower by PMA a month ago and as a result I have been incapable of listening to any other amp including my own Gainclones for more than a minute or two, the difference is obvious to me now- effortless listenning; while listenning to the MPF I seldom touch the seek pointer in my media player. And as the article in the ESP page says, MPF made it effortless coz there was no ringing or overshoot; my ears could almost read the lyrics! 
This is proof enough that the MPF is not a bluff.
Well, ya I did make the Death of Zen a couple of days ago(I wonder why coz I was so much happy with MPF, is it curiousity or the DoZ article's rashness to the MOSFET followers, or both? whatever).
I used TIP3055(fT-3MHz) TO218 devices(those 30MHz things aren't available here). I ran it from the same 40 volt capacitance multiplier supply which powers the MPF and connected to the same 8ohm fullrange which was previously being driven by the MPF. I even used the same heatsink for DoZ. Setting the pots as said I started playing my favourite pieces one after another. The immediate realisation was hollow bass. The guitars sound less detailed, the pianos kill my ears, the violins bleed and scream(even in low volume), the sax and the clarinet lose their "touch" and every Indian instument fails to even initiate a good impression; start to end- a flop!
Then i wondered how much it could abuse the vocals. I tried some Indian as well as various foreign recordings. "The answer is... Horrible"(quote from the DoZ article ). 
Conclusion- I think DoZ is just a class-a amplifier which should only be tried to see(and hear) how an amp with "minimal" global negative feedback in the topology and the "ultimate" global negative word "Death" in it's name, makes your favourite music sound nasty.
The DoZ made me realize that even true class-a amplifiers can sound bad.
Thanks Rod.
This is proof enough that the MPF is not a bluff.
Well, ya I did make the Death of Zen a couple of days ago(I wonder why coz I was so much happy with MPF, is it curiousity or the DoZ article's rashness to the MOSFET followers, or both? whatever).
I used TIP3055(fT-3MHz) TO218 devices(those 30MHz things aren't available here). I ran it from the same 40 volt capacitance multiplier supply which powers the MPF and connected to the same 8ohm fullrange which was previously being driven by the MPF. I even used the same heatsink for DoZ. Setting the pots as said I started playing my favourite pieces one after another. The immediate realisation was hollow bass. The guitars sound less detailed, the pianos kill my ears, the violins bleed and scream(even in low volume), the sax and the clarinet lose their "touch" and every Indian instument fails to even initiate a good impression; start to end- a flop!
Then i wondered how much it could abuse the vocals. I tried some Indian as well as various foreign recordings. "The answer is... Horrible"(quote from the DoZ article ). Conclusion- I think DoZ is just a class-a amplifier which should only be tried to see(and hear) how an amp with "minimal" global negative feedback in the topology and the "ultimate" global negative word "Death" in it's name, makes your favourite music sound nasty.
The DoZ made me realize that even true class-a amplifiers can sound bad.
Thanks Rod.
The main different from my view is the additional buffer transistor Q2 used by the DOZ and not used by the JLH (schemas post #4).
Where is to read more exact explanations regarded this additional transistor between the phase splitter transistor and the output power buffer ?
Thank you for your advices.
Here the according URLs of both projects:
JLH Class-A
The Class-A Amplifier Site - JLH Class-A Update
http://www.tcaas.btinternet.co.uk/jlh1969.pdf
http://www.diyaudio.com/forums/solid-state/3075-jlh-10-watt-class-amplifier.html
DOZ
Death of Zen - A new Class-A power amp
http://www.diyaudio.com/forums/solid-state/208076-death-zen-15-watt-power-amplifier.html
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