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Oh man, I broke my class D amp. Make fun of me. Then help.

So... I made a new pair of super fancy interconnects this evening. Of course I was on auto pilot on the second one, especially the last connector. And, of course I always test my DIY cable projects before install..

Except tonight. Installed the ICs and all I hear is clicking. Not loud, and independent of the volume on the pre. Independent of source. Weird. I shut everything down and figure maybe, for the first time ever, I miswired a cable, so I pulled the new ICs and tested. Sure enough, I crossed my signal and ground. I repaired my mistake, reinstalled and now the amp the crossed IC went to is jacked.

The volume is much lower than the other channel, there is distortion during strong high frequency signals and the sound drops out during strong low frequencies signals. The other amp is fine. I swapped channels coming from the pre and the problem stayed with the amp. I doubt it is the speaker, as there were no sudden loud noises. Just the innocuous clicking...

So, what did I fry? Some kind of capacitor? Or everything? The amp is a Ghent audio monoblock, which is class D and uses ICEpower a/s modules. It is a GA-M500. Here’s its webpage: https://www.ghentaudio.com/amp/ga-m500p.html

I’m fine sending it in for repair, but if anyone has either knowledge of amp design or the unfortunate luck to have done this, I’d love to just fix it myself and save a lot of sending it around the world. Also, feel free to make fun of me. I deserve it. Such are the consequences of hubris.

If you’re wondering, I used KLEI pure harmony connectors, which have two identical looking tabs, one on each side, to solder the signal and ground to. If you look even remotely closely you can easily tell which is the ground.. but it’s not at bad as if I had done this with a more traditional RCA connector. That would have been really pathetic. 

Also. Recommendations for repair shops please.

Ugh.

128x128toddverrone
asvjerry's avatar
asvjerry
4,664 posts
 
Hey, Todd, cheer up.  Everyone has had the experience of screwing up but it takes an admirable part of one's personality to admit it in public.  So, I'll just *S* and say "Welcome to the club.  Try not to come here often, right?" *L*
Related recent event...my spouse 'does fish'.  Added 3 angels to her 55g. tank to join 2 angels and 2 algae eaters.  Had planned and ordered additional plants and enhanced lighting to support all...but hadn't covered that part of the 'equation' yet...
She got to watch as all 7 fish literally suffocated, slowly...heartbreaking for the both of us.

At least you didn't kill anything.

If there's an applicable moral here, double check yourself and everything.  Then do it again if it's expensive or a PIA to fix or replace...

...because sometimes it's irreplaceable....;)
spatialking's avatar
spatialking
610 posts
 
Todd, it can't be anyway worse than me when I adjusted the bias on a Class AB amp and shorted the heatsink to ground because I was using a non insulated, very long screwdriver - the heatsink was at 50Vdc, not ground like I thought.   That was an expensive mistake.    Back to your problem, I don't exactly see why reversing signal input and ground on your interconnect would fry your amp.   Essentially, what you have done is shorted the input of your amp to ground, there is nothing wrong with that, and shorted the output of your source to ground.   Now, that last one could be a big deal, depending on your output stage design.   A direct coupled output stage, without an isolating resistor, could blow the stage.   Before I sink money into your Class D amp, I would verify the source is still operational and in good shape.  Try plugging the output of the questionable channel into the input of the amp that works fine and see what you have.   The idea of looking in your amp for something obvious like a fried resistor or blown copper trace is a very good idea, btw.
kdude66
1,200 posts
 
Oh my,
The advice in trouble shooting a class d Amp just blows my mind.
toddverrone's avatar
toddverrone OP
840 posts
 
Wow, thanks everyone. Good to know I’m not alone! Yesterday I did the best thing one can do after screwing up royally: I took my kids and their friends to a beautiful Ozark swimming hole and we spent 9 hours basking in beauty and playing in a waterfall.. ahhh.

@atmasphere I did try different Interconnects ​and had the same problem. I’m sure the one I built is good now. I fixed the switched connection and TESTED THE DAMNED THING FOR CONTINUITY!

@spatialking I don’t see why a weak voltage like a signal would screw anything up, but it has. Like I said above, I tried other sources and different cables, moved the amp.. it’s the amp for sure. And man, yeah, shorting an amp in that fashion seems much more exciting and dramatic!

@asvjerry those poor fish...

Greg - the clicking was only there when I had the faulty IC connected. Then it just sounded like garbage and eventually stopped working most of the time. The problem I have is that the B&O module used in my amps isn’t made anymore. The only one I’ve seen is on eBay for $900!

On a positive note, my wife, the breadwinner, just said "buy some new ones". Also, a friend who works with class D amps in an industrial setting told me that he and his electronics guy could fix it. I was dubious, but he’s insistent, so we’ll see.

And, to and a big fat twist, I came home from the climbing gym last night to find my wife still awake, looking through my eldest son’s phone. She found all kinds of interactions with racist, white supremacist scum on social media and some porn. It’s going to be a long summer.. and it definitely put a broken amp into perspective, in terms of the crap I’m going to have to fix.. teenagers. Jeez.



atmasphere's avatar
atmasphere
11,834 posts
 
@toddverrone, OK- the next thing is to swap the interconnects left for right at the input of the amps.

You want to make sure that its not the source that got blown up, and FWIW its output got shorted to ground with that initial mis-wire.

So if you do that swap and nothing happens then the amp somehow failed (could be a blown fuse BTW).

But if the problem moves then the amp is off the hook and the source needs to be examined.

Good Luck! - on all fronts!
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