DC leakage from power amps

This happens on both sides, but it has been more on the left channel lately

What preamp are you using? The DC leak might be the preamp! My tube preamp had a DC leak!

I found this link doing a search.
http://audiokarma.org/forums/index.php?threads/amplifier-distortion-dc-offset-and-you.5634/

As a semi-poll, I’d like to see those on this board whip out their multimeters and take a look at the DC that is being presented to the speakers. This means..

1. Speakers disconnected (or connect the meter to the ’B’ speakers and set the front panel speaker control accordingly)
2. Input set to an unusued position (not Phono)
3. Volume control at minimum.
4. Balance in center
5. Tone controls either defeated or set to mid position
6. Set your meter to read DC, and set to a low scale (300mV scale is common) Connect directly to the Pos and Neg of the speaker terminals
7. Give the amp 10 minutes to settle. Report back...I’d like to see how healthy all these old amps are.

If you read:

0 - 15mV: Damn good!! If you read ’0V’, you may have a capacitor output, or your meter is set wrong

16mV - 50mV: An acceptable value, especially at the lower end of this range. 2nd harmonic distortion is probably twice to four times what manufacturer’s spec calls for at higher frequencies. Probably not audible, as the distortion is mostly in the upper octaves. At the upper end of this range I begin to raise an eyebrow. :saywhat:

50 - 85mV: Something is certainly amiss, and while this is not enough to put your speakers or equipment in jeopardy, the amp is running nowhere near where it should. I’d venture to guess that most of the DC-coupled amps that are in use by forum members here fall into this range.

100mV to ?: A high enough voltage will cause the DC protection to kick in. This happens at a level determined by the designer, but is usually equivalent to about a diode drop (600mV)or so. Needless to say, if you are listening to an amp with 100mV or more of DC offset, you have no idea what the amp really is supposed to sound like. Indeed, some amps without a differential input are actually designed to have a bit of DC at the outputs, but this is triple-rare, and I don’t think anyone here owns one. (in my book it’s piss-poor design, but if you can sell it WTH..)

Note, I personally do not know if the guy's method for testing for DC offset at an amp's output/s is correct or not.
.

One obvious question, how loud are you listening to your music?

The midrange is unlikely to be the place where you blow a resistor, but I'd have to know the schematic. Much more likely to happen on the woofer, but I digress.

Put a meter on your amplifier output and measure. DC is easy for any multi-meter to read, but make sure it has a mV range. I had an electrician's meter that could only measure to 0.1V DC, not good enough.

Best,

E

I think you are looking in the wrong direction. A little bit of DC leakage is not going to blow fuses and drivers in a speaker that is designed to handle 100's of watts of power. At least I assume a $50K speaker that doesn't have a stated maximum power can handle any reasonable amount of power. The likely culprit is you listening at extremely high volume levels. Since you don't mention what you are listening to and at what volume levels that is just a guess, but much more likely scenario than the amps leaking a bit of DC