I currently own a BRZHIFI A20 which I bought as an experiment. It is my first tube amp. I noticed it is VERY similair in design to the Reisong A10 PCB version. In fact I dare to say they are the exact same amps! Only differences being in terms of quality. Are they the same?
I want to experiment with upgrades to see what it can do. Replacing the caps with film ones should be easy. But what more can be done?
The capacitors (the 3 larger) in the centre section (around the rectifier tube) are your power supply capacitors.
The smaller capacitors are for the driver tubes (the 6ax7 equivalent) it appears on this board they are not driving both sides of the driver tube (6ax7) and not picking up the added capacitance from the tube (each and every tube has a capacitance value), so they had to add some. Of interest to note, I don't see a capacitor on the EL34's, the spot is there for them, but it is empty. The rectangular boxes are your coupling capacitors (marked .22uf), if a gain is to be had by changing capacitors, these are the ones to change.
Somebody posted about these things being made in a few different factories and I believe it.
The a-10 and the a-12 differ in the driver tubes, the a-10 uses a 6n2p (6ax7), and the a-12 is wired to use a 12ax7.
Honestly, the easiest a-10 mod is a pair of Russian 6n2p (6ax7) tubes for drivers, and a pair of 6v6 tubes (Russian ones again if you can find them). Hook your 8 ohm speaker load to the 4 ohm terminals.
You can do the entire a-12 mod if you like.
I kinda wonder what the Russian 6v6 tubes sound like and I ordered a pair last week.
I have taken some pictures of the PCB. What do you think? My main question is trying to figure out what the capacitors are for.