Dc voltage sent to my speakers

Some amps are heavily current limited and under low impedance/high output conditions will clamp their output so that the output resembles straight DC or clipping (or a square wave, for that matter). Because this keeps the amps VA output within safe marginsn, nthis is an amp protection scheme, not a speaker protection one. 

Some amps are heavily current limited and under low impedance/high output conditions will clamp their output so that the output resembles straight DC or clipping (or a square wave, for that matter). Because this keeps the amps VA output within safe marginsn, nthis is an amp protection scheme, not a speaker protection one. 

If a preamp is outputting a little DC, is it always because of faulty output coupling caps?  Should those caps always be expected to block all DC?  I had one tube preamp that would trip the protection circuit of one of my amplifiers due to DC leakage, and I'm wondering if replacing the output caps would have fixed the issue.

@ketchup - Even with the best caps there can be some leackage, but usually in the microvolts ( < 1 millivolt ).

Yes, it's very common for the output caps to leak DC and need to be replaced.  Not saying everyone's caps will fail, but that this is a very common reason techs see tube preamps. 

Should also note that SS amps also may suffer from small imbalances, usually under 0.1 V though.