Just an update, I have changed the opamps from three JRC5532 chips to two OPA2107AP and one LM4562NA as buffer. It seems to have improved, especially the muddiness. I also upgraded the two 470uf @ 25V caps to 2200uf @ 25V caps. The pop sound when turning on the amp is not as bad now, which means I can keep the headphone plugged in instead of putting it in each time I use it. The bigger caps also retain the current for longer resulting in the amp working for a second or two after I have switched it off. The LED light would be still on until 10 seconds later.
I got a $3.5 multimeter from eBay a while back, but it didn't work at all. Luckily, I got a refund. Then I proceeded to buy a $7 one (BEST A830L to be eact) from DinoDirect, which arrived at the post office today. Since I picked it up, I have been playing with it on my amp. It's so fun!
I tested the voltage of the wallwart supply. It's 11.5 VAC despite rated at 9VAC. The voltage at the regulators is about 13.6 VDC with a dropout of around 4.65 VDC, so the output voltages are +8.9V and -9V.
I believe I can safely use 12V regulators at this point in time, and I will report back how it turns out after the final mod.
No before photo, but a after photo here for you.
Edited by kingpage - 6/9/11 at 2:53am
