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You make me a bit worried about your warning about passing DC to my speakers that they will get wrecked, how bad is that?
Bad as in permanently kaputt.
Since I am a bit technical guy, I actually don’t understand the concern of DC signals? DC signal is, at least theoretically, nothing more than just the positive half of an AC signal :-) For which part of the loudspeakers would it be the killer? The subwoofers or the tweeters?
You might kill your woofer first. Due experimenting may proove me wrong though ;-)
Problem with DC on any audio signal chain is that it does not alternate and thus cannot be heard. More specifically it takes away from your headroom/dynamics usable for audio and puts useless stress on your speakers. That is why P.A. power amps usually have steep hi-pass filtering to void any DC in their output. (More smoking details on speaker death by DC on demand.)
-- GarfieldModular