PG and SG

[Raka]

I didn't notice the power-down problem. You can care about the switch on and off, but this one...

I'll provide a delayed power-on for the LM. I'll search over the ESP excelent page.

 

[carlosfm]

Raka, with the PSU I am using now, I get around zero mV on the output and just a very brief rise when I power down the buffer.

Last week we had a power cut here, so both sections (buffer and LM3875) went off together and then powered up together about 5 seconds later. No damage was done although as a matter of good practise, I would always switch the buffer on first and off last.

Nuuk, you can try a series resistor with the PSU lines entering the buffer's board.
Let's say between 10 to 47 ohms.
It's a common practice with op-amps, it isolates the device from other devices sharing the same PSU (not in your case) and reduces the power-on "bang" .

 

[Raka]

Nice suggestion

Does it reduce the bump enough to forget about tweeter protection?

 

[carlosfm]

Nice suggestion

Does it reduce the bump enough to forget about tweeter protection?

I'm afraid not.
But I wouldn't use a tweeter without a cap anyway.
Even if it's a big cap, with a roll down frequency much lower that normal, I would definitely use it.
It protects your sensitive tweeter from DC.

 

[Bricolo]

stupid question...

In point-to-point sometimes it's difficult do get the 1000uf caps as close to the chips as they would like.
On the breadborad modules that I usually make, the 1000uf caps are very close to the chips, but right at the pins I bypass with 0.1uf polyester caps.
You may try to do that, maby that's the problem.
It may seam to you that the caps are close enough, but at a few cm from the chip they are too far.
If you can't get them closer, bypass.

When you say bypass, are you meaning "a 0.1uF cap between + and gnd, and another between - and gnd", or "a 0.1uF cap between + and -" ?

If it's between + (or -) and gnd, how do you connect them right at the pins? (connecting the + or - is no problem, but where do you find the gnd directly on the pins?)