I'm trying to build a simple but very good amplifier with a refined sound, not class A, about 15-20 Watt, for example like NVA AP10. I'm looking for the schematics in web, but there aren't or I'm not able to find them.
I'm not sure what your level of knowledge/experience is but....
I'd recommend building one of the designs published here on the forum. That way you have the support and help of the designer and other builders and users.
The simplest option would be a chipamp. If you're feeling more adventurous and want to try a discrete design, perhaps one of Carlos(Destroyer X)'s designs would be suitable? e.g. The Dx Blame ST. Details of other DX amps can be found on Greg's website here (and are discussed in various threads on the forum).
two years ago I had built with my friend some tubes amps (211-845 and others), I rejected them, they are too hot expecially in summer and they require a lot of time before to go in ideal conditions , so I turned to build a Shigaclone.
It sounds good, but not so smooth and refined as the tubes amps.
A pair of 2SJ162/2SK1058 biaised at 120/150mA
driven by a symetrical differential front end, since this topology
suit better to powermos, a +-25V supply ,and you ll have a good
sounding 20W amplifier...