You don't understand "full volume".
Music and speech make pulses of power with much less power in between the pulses.
The average output power is maybe only 1/5th of the full volume.

But it is nice to have a power supply that is capable of testing the amplifier properly at continuous full power. A 2A transformer will be fine.

Did you test the hum by shorting the input to ground? If the hum continues to be bad then my filter modification won't work.

 

No I have not tried that at all. What is the proper steps or where do I go to learn.
New box: Metal - three prong plug - 1 Transformer - 1 power supply board - then two
existing or mods your way 12 Watt amplifier boards - 1 dual RCA jack music entrance -
Exit music thru speaker jack (Dual). Right now amplifier project powers two pairs of 30Watt
speakers. Thankyou for the advise.