Dc voltage sent to my speakers

@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.

Thanks a ton my Audiogon family . I can't scream this loud enough I SHOULD HAVE USE A VARIAC . Because the tube pre amp was in storage for years.

I for one would be really interested in hearing the results of actual analysis of the preamp and amp. There are lots of great theories here, it would be really be good to hear what actually happened.

I don’t think the take away is to go buy a VARIAC. First, I have never heard of a preamp frying a set of speakers. But I am not versed in practical electrical engineering. But, even if this is a thing, then the take away is to buy from a reseller that verifies it functions properly (like Echo… and a host of others) or to have the device checked over by a audio shop. 

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.