Amp6 Basic assembly story: Fast clicking sound without C1819

[Krille]

Got my Amp6 yesterday and started building it right away, following the guide for the amp on this site and also Tuo's blog about the alternative assembly sequence to make it as easy as possible.

Well, I got it together and started the testing procedure WITHOUT the C1819 cap as told, to not risk frying the chip if something was wrong. Measured ampere in idle and then in muted state and everything seemed okay. Shut down the power and connected some speakers and using my phone as input I then turned on the power, un-muted the chip hoping to hear some music and feeling that wonderful feeling when you completed something that works... but no, all I got was a fast clicking sound. Faster than 1 click/sec.
So I checked every solder, measured every resistor and diode so everything was put right and cleaned the board but I still got the clicking. I sat one day trying to pinpoint the fault, searching the forums trying to find something I had done wrong hoping it was an easy fix but no, I just couldn't get it working properly.
The REF voltage was 1.140 so that seemed fine and I could not find any short anywhere. Connected the LED signaling faults but I didn't lite up.

Just now I was getting pissed of and just connected the last thing i hadn't connected hoping that would solve everything and magically repair the amp, and that piece was the C1819 cap.
And yes, music was heard! I almost cried!

So I read wrong somewhere tabing through 2 guides that the cap weren't needed for the testing, even when you connect speakers. I'm so stupid

But anyhow, under the time I searched the forum for help I found some threads about this fast clicking sound with no real solution, so I just wanted to share my stupidity to also share the tip of checking the output cap, it might have gone to hell.

[xrayspex]

Congratulations! C1819 is normally not needed for testing. Apparently your power-supply wasn't stable enough.
Enjoy your new amp

[Krille]

I sure will! Boombox time ;D

That's odd, it's an laboratory power supply so it should be stable, didn't notice any voltage fluctuations when I measured under load. But I just assembled one more amp6 with the same problem, and the same fix, so something isn't right with it I guess. (Double-checked every part before placing it the second time around to be absolute sure I hadn't missed anything).