AMP3 playing, but no bass

[coredump]

Hi,

I managed to get my AMP3 kit working at first try, but there are two things that bug me:

* the music has no bass to speak of, the whole presentation is like through a bad telephone line
* when muting the amp, the output DC rises from about 70mV to 5V (on both channels)

Any hints where I could have cocked up are appreciated.

Thanks,

Oliver

[coredump]

16 (BIASCAP) is 2.38V
C14/C15 are about 2.44V
10/11 and 14/15 are 0V
1 is 5.12V
4 is 5.12V
9 is 5.12V
Voltage across the diodes is between 5.05V and 6.55V

The amp also seems to be much too quiet; I have to turn up the wick to about 03:00 in order to get a decent volume on my test speaker. Hrm. :-/

[coredump]

The PSU should be OK (12V/3A switcher for external hard disks), and the amp is definitely not clipping.

[coredump]

Removed every trace of flux... problem still there.

[mb_rp]

Hmmm... perhaps you should recheck the orientation of all the output diodes, not only visually, but with a meter? The obvious pins on the input section seem to have the correct voltages.

[coredump]

mb_rp,

quote:mb_rp wrote:
Hmmm... perhaps you should recheck the orientation of all the output diodes, not only visually, but with a meter? The obvious pins on the input section seem to have the correct voltages.
thanks for your hint; however, the diodes look fine on the meter. The problem exists for both channels, I guess this rules out a wrongly labelled diode?

Thanks again,

Oliver

[coredump]

Righty right... I guess I'll have to bite the bullet and re-solder every component but the chip and the diodes.

[coredump]

Solved. :-)
Pins 27/28 had insufficient contact (not enough solder). Now it's playing fine. This is my first Tripath encounter, and I must say that I'm seriously impressed.

During my resoldering orgy I managed to rip the end cap off of one capacitor (C29). I replaced C29 and C30 with 33nF Sibatit capacitors (non-SMD, the closest value I had). Is this critical?

Best regards,

Oliver