Tweeter protection in balanced GC?

[terranigma]

I'm going to build a tri-amp speaker with LM3875 with balanced signal. My power source will be based on LM338 regulators. I just wonder if power-on tweeter protection is a must for this kind of attempt even using balanced signal.

[Mooly]

Tweeters are AC coupled, so unless the amp is oscillating (unstable) there is no problem.
DC faults won't affect it either, the cap protects it.

[terranigma]

I'm going to drive tweeter directly with a LM3875 which means there will no cross-over network or a cap between tweeter and LM chip, if I don't put it myself.

I just wonder that using balanced signal as source (instrumentation amplification) is not enough to protect tweeter from "thumps".

[Mooly]

Understand you... definite risks in that case.
You will have to see how the amp behaves under all conditions of use and also abuse... such as switching on/off and on again rapidly.
Also can anything before the LM3875 cause any thumps etc... switching preamps on off for example.

A cap is the best most foolproof solution for protection.

If you don't want that then a relay delay with a quick and reliable "reset" so it always gives the full delay no matter how quick you switch on/off.
Same for the outputs of any preamps, there should always be zero noise at power on/off.

[terranigma]

Thank you for that clear advise. I'm some curious about to not using caps and opamps on signal path. This is what makes me to use balanced signal and build a tri-amp active speaker system.

My source is a modded AK4396 based sound card. There is only one resistor between LM chips input and dac chip's each output.

I should try a cap first, then find a solution with a relay like you mentioned above.

[Mooly]

When it comes to speakers it's better to be safe than sorry.

Why not try a cap and have a switch across it to short it out when the amp is on... see if you hear any difference.

Tweeters are pretty fragile things, the voice coil thin and easily burned out. Make sure the DC offset of the amp is zero too, a few millivolts won't cause damage, it would have to be volt/s to do that, but it might ? cause non linearity in the speaker.
Not sure about that last point... I raised a thread on it ages ago... opinions were mixed.