Dc voltage sent to my speakers

My experience with tube preamps is very limited, but the one or two that I played with had a tiny bit of DC on the output.  In the range of 5mV or less.

@erik_squires Some preamps like the Dynaco PAS3 make a small amount of DC like that but its not on account of the output coupling cap. The circuit employs feedback to the cathode of the input stage so there is a small amount of DC on the output as a result. As you already know though, its harmless.

this is pretty much what I do now-a-days, but how much time should it take the preamp to stabilize?

@immatthewj Normally about 30 seconds; your preamp is an exception. But if you're talking about a tube power amplifier its not a concern since the tubes can't be damaged that easily. 

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.

@erik_squires @ketchup Unless the coupling caps are really old, its unlikely there's any DC at all at the output.

However, when you start up a tube preamp, there is a voltage rise on the input side of the coupling cap. A corresponding rise will occur at the output which follows an exponential curve. Usually a resistance is supplied at the output of the preamp to discharge the part as the tube warms up.

So if the preamp is turned on after the amp is already on, the amp is in danger! That is why the common protocol is the preamp of any system (tube or solid state) is always turned on first and allowed to stabilize prior to powering up the amp! It really doesn't matter if the preamp is tube or solid state in this regard.

Um, not the one's I've seen especially "high end" amplifiers that pride themselves on not having any.

@erik_squires 

Sounds cringeworthy to me- yikes!

Most solid state amps have a protection circuit to prevent damage to the speaker in case of output section failure (which is how they typically put out DC that can damage speakers). So this is a bit unusual!