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DC leakage from power amps

I am hoping to get some advice on how to check for dc leakage from my power amps. I have a pair of Bryston 28B SST2 mono blocks, powering a pair of Wilson Maxx2's. The Wilsons drivers are protected by resistors, acting as fuses. I have been blowing quite a few of the mid driver resistors, valued at 5.8 ohms. Last night I lost another mid resistor cluster on my left channel ( there are 4 wired in a series/parallel configuration), and what I thought was a tweeter resistor, but upon replacing that single resistor (4.2 ohm) with a fresh one, still no tweeter. I was fed up, and did not investigate further, but fear that I may have a dead tweeter, or worse, crossover issues. I am no tech expert, but am concerned that I may have DC leakage from my Brystons. I live about a 4 hour round trip to the Bryston facilty in Peterborough Ontario, and have lots of warranty left, but don't want to pack up the beasts and have them inspected if I can confirm on my own, if there is a DC issue. How do I go about checking the amps at home, and confidently knowing if there are amp issues, or not. If the amps are faulty, I will return them for repairs, but would like to eliminate/confirm the issue at home. Any help will be greatly appreciated.

128x128crazyeddy

Showing 3 responses by atmasphere

atmasphere's avatar
atmasphere
11,633 posts
 
Always happy to help!
atmasphere's avatar
atmasphere
11,633 posts
 
The SPL meter sounds like a good idea.
I think that would be a good idea too.
atmasphere's avatar
atmasphere
11,633 posts
 
This problem is **not** caused by DC!!

The speaker has crossovers that prevent the midrange and tweeter from seeing any DC- even if the amp had a serious failure that put out so much DC that the woofer was fried, the midrange and tweeter would still be OK.

The woofer is always the part that fails due to DC, but a few millivolts is not going to harm it in any way. It has to handle a lot of power from the amp and a few millivolts of DC is nothing. IOW, that's not the problem.

What is going on is that the amplifier is not making enough power to make the desired volume. So as a result, it is being overdriven pretty hard, and the harmonics of the distorted bass notes are at frequencies that the crossover allows into the midrange and tweeter. Since these drivers normally don't have to handle such large amounts of power, they get burned up.

The solution is either get a bigger amp (start out with at least twice as much power) or put fuses in series with the midrange and tweeter drivers to prevent damage. Or don't turn it up so loud, or get a speaker that is more efficient, so you don't have to clip the amp.


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