2. amps-preamps
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A worse feeling than burning out your amp?

Last night I was planning to get back into making digital music and began setting up my laptop with the necessary software. I had my audio cable (1/8" connector) plugged into my Macintosh, which was playing mp3s. The laptop was ready to go, so I unplugged the cable from the Mac without turning the amp off, which I've done dozens and dozens of times before; BIG mistake. I heard a very loud buzzing sound that lasted about a quarter of a second, followed by a loud pop. I went over to the amp and could smell electronics burning. I turned the amp off and back on, after which I noticed that sound was only coming out of the left channel and it was very broken and full of static. Also, it doesn't matter which input is selected, it plays all sound coming from all inputs now. This integrated NAD C 340 amp is no longer good as a preamp either. What a horrible feeling, but it could have been much worse (my speakers could have blown out!).

Has anyone ever done something similar to their amp and attempted to fix it? I'm at least going to open it up and have a look before I trash the thing. The only bad part about all of this is having to wait several months before I can afford to replace this unit. For now, it's back to the old mass market Kenwood receiver....
jwglista
entrope
482 posts
 
A worse feeling-

Getting some new gear from UPS (read OOPS) and discovering it has been broken in shipping. You never even get to try it and then have the hassle of contacting the seller and working out a resolution or freight claim while the broken gear sits silently in the corner mocking you for using UPS.
chadnliz
3,736 posts
 
I ALMOST did some major damage after swapping inter connects, I forgot to turn on one of my amps (the 2 channel main) scratched my head and turned volume way up to see if I could hear any noise in speaker...went for the power buton and at last second remembered to turn down volume....that scared the hell out of me and I didnt even do anything...but man it was close.
P.S. I am going to keep a better eye on bananna plugs!
stevemcx
159 posts
 
From your description it sounds like you lost the ground connection through your interconnect cable, leaving just the "hot" connections on both channels. This will cause most amplifiers to oscillate, often resulting in damage to the speakers, or amp, or both. It would be nice to think that the internal fuses had protected your NAD amplifier, but the fact that some parts overheated suggests otherwise. If you're feeling adventurous, you can check for blown fuses and replace any you find, and try it again. Otherwise, a visit to your local audio hospital is called for.

Note that this problem may occur again with the same front-end gear, regardless of what amp you are using. Losing both ground connections is rare with separate interconnect cables, but becomes more of a problem with “Y” cables - especially with mini-plug connectors. Check your cable carefully and replace it if you think it might be bad.
gmarcotte8f97
66 posts
 
Chadnliz, i did not know that was a condition that we need to avoid (turning on amp when voulme is turned up). i will keep this in mind.

i have fried a pair of channels when i ran built in test tones on an avr. rear speakers had been modified and i'm not shure what the ohm load was. i'm still looking for my multimeter to this day. good thread.
chadnliz
3,736 posts
 
I cant say it would be a problem. I hope that it wouldnt but I had the fear in me all the same, the amp was under the Processor and I just didnt notice, but I had turned volume all the way up to try to hear that tiny bit of noise I get when it is up without material playing. that being said I am still glad I caught my mistake.
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