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crippledchicken 10th January 2007 03:45 PM

Sub Amp Problems Thanks!
hello, i have had two Parts Express plate amps the SA 240 WATT modelsthat have both, went out on me. i drive them from the left & right speaker level outputs from my Onkyo M-282 2 channel power amp. my question is, could i maybe have some type of problem with my power amp output signals which caused the left channel input on the plate amp to go out? the first SA 240 watt amp that went out on me had problems with the output section of the plate amp. the measured dc offset levels of the Onkyo power amp are 4mv. on one channel and 7mv. on the other so i wouldn't think that would be a problem as low as they are. i thought maybe, the problem could be oscilation but, the power amp outputs and heat sink just barely get warm to the touch also, i never drive the system hard at all this second amp input went out during low volume watching King Of The Hill on satellite LOL! i could try running the replacement amp when it gets here at line level input from my Adcom GFP-565 Preamp outputs but, every sub amp i have ever driven that way seems to lack the output i get when fed from speaker level input. also, the sub doesn't seem to blend as well with my main speakers. i don't have a scope to test for oscillation. any ideas of what else i could maybe check would be appreaciated. Thank You! :confused:

unclejed613 10th January 2007 05:18 PM

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if your plate amp inputs are capacitive in any way, it could be the onkyo amp oscillating and frying the input stage of the plate amp...... since 90% of all amps out there have capacitively coupled inputs, this is highly likely. use a resistive voltage divider with an 8 ohm dummy load

crippledchicken 10th January 2007 06:17 PM

hi and thanks for the advice. i may try using the line level inputs feeding from an extra set of jacks on my Adcom preamp first, since i haven't tried this particular amp on this Dayton 15" DVC by line level yet. if it's a much safer method to feed it that way, i might just run the sub with line level input. Thanks again! :)

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