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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
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jea48
4,483 posts
 
@crazyeddy,

What are you feeding the two amps with? I assume each amp has its’ own 120V 20 amp dedicated branch circuit. Roughly what is the distance, length, of the wiring from the electrical panel to the wall receptacle outlets? What are you using for receptacles? Did you use #12awg bare minimum wire size or increase the wire size to #10awg? Are you using the stock power cords that came with the amps? If you are using after marker power cords, made by who, model?

It would appear these amps need plenty of mains power if you are pushing them hard. If the mains voltage is dropping due to VD (Voltage Drop) on the branch circuit wiring it may be having an impact on the amp’s ability to deliver their full rated power.

You can check the mains voltage at the wall receptacle with your multimeter.
First check the voltage with the amps at idle.
Check the voltage again playing music at a moderate level.
Check the voltage playing music loud at the level you like to hear it at.
Is the voltage lower but holds steady?
Is the voltage lower, bouncing around, with the beat of the music?

Specs
http://bryston.com/PDF/brochures/SST2_875HT_BROCHURE.pdf


https://www.youtube.com/watch?v=TOof73b60E0

Review
https://www.stereophile.com/solidpoweramps/108bry/index.html

You may find these posts of Charles Hansen of interest concerning "fully balanced from input to output".
https://www.audioasylum.com/forums/amp/messages/22/220523.html

Jim
herman
2,259 posts
 
hey Ralph, I agree about the DC, but  he has monoblocks that will do 1800 watts into 4 ohms so I don't think bigger amps is the answer

Could it be the line sags so low they clip? Seems like the lights would dim if that happens but never seen that so don't know. 

my theory is it is playing much louder than he realizes
crazyeddy's avatar
crazyeddy OP
381 posts
 

@jea48  I  do indeed have 2 dedicated 20 amp circuits, and am fortunate to have my main panel box in my listening room, in fact, from my panel box to my outlets is a direct vertical drop of approx. 4 ft , and yes #10 awg. None of my power cords are stock. All are AudioQuest NRG-4's, and all are either 3 ft, or 6 ft.

Power out of my conditioners is a rock solid 120v, although I have not checked this under high volume conditions.

It all just may be that I am the culprit here. Herman makes a good point, that it may be louder than I realize. After so many years of working in extremely loud industrial settings (metal fabrication) and add to that my years as a hard rock guitarist, some hearing loss may be more than I realise. I do have a SPL meter, but haven't used it in years. Perhaps I will dig it out of storage and see what actual values are being presented in my room. Will follow up with these readings tomorrow.


Thanks all.......

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