AMP 4 delayed start up on one channel

[ndh99]

I have a working Amp 4 powered by a laptop power supply 19V 4.7A. I left out the D99 Rectifier and did not install the Large Caps C1000 C1001. After 20-30 hours of use one channel started delaying start up for a few seconds. So after the on/off switch unmutes I get a "pop" out of one speaker and it starts to play and then 3-10 seconds later the other speaker "pops" and it starts to play.

Any ideas on how to correct this minor issue? Or is it just a problem with the power supply being below the 20V minimum?

[V-bro]

Yes, sounds like it, though it can be modified to operate at as low as 10V (even lower...) Here it is probably the relay cutting out. I can't really say from the top of my head what to change...

Perhaps it is a better idea for the sake of power and good operation to just swap the PS....

[krilli]

I think it's roughly like this - If you have put a jumper instead of the resistor near the relay power pins, then you either have to raise the voltage over the relay, or get a different relay - one that operates on a lower voltage.

(p.s., the amp sounds even better with higher voltage )

[krilli]

Hey, here's a thought: - Can only one side of the relay actually switch without the other side going?

[V-bro]

Hey, here's a thought: - Can only one side of the relay actually switch without the other side going?

I think there actually is a little margin for unequalness in the contacts.....

[ndh99]

Thanks for all the comments, I got it fixed. It did not end up being a power supply or relay issue. It was a bad solder joint on the tripath chip on the bottom of the board. After some additional problems surfaced that pointed to loose connection on the chip I pulled the board and carefully reflowed the joints. Re-cased the board the delay problem completely disappeared, they amp also seems to handle higher volume output and sounds better in a hard to describe way.

As these forums remind us... you can't check the solder joints enough!

[V-bro]

Great job! Thanks for reporting!