Help Me Please

[Greenleef]

I'm in over my head with my install and despite countless internet searches I haven't been able to find the answers I need. I'm also new at this so my apologies if this is a dumb or obvious inquiry. Thank you in advance to any and all that take the time to read this post and respond to it. I have two amplifiers grounded together at the rear of my vehicle. a 2-channel class AB amp for tweeters and a 4-channel class D for the door speakers. The tweeters sound fine but the door speakers have a constant hum/buzz sound in the 4-5 kHz range. It doesn't change with acceleration or even when the music is paused but it does increase and decrease in volume when changing the amp gain. I ran the door speakers through the other amp to test them and they sound just fine. I don't think it's a ground loop issue, but out of curiosity, if multiple amps are grounded together can just one have grounding issues or would all of them? As far as I can tell, signs are pointing to a bad amp. I've read that class D amps can have issues at higher frequencies but everything I read also said that typically happens to low quality amps. I'm using the Alpine X-A70F and it's only about two years old. All the amp troubleshooting tutorials I've looked at don't mention the class of amplifier in reference so does it really matter in regards to repairs? I'm not going to open it up but is there anything that I should investigate on the amp, to make sure it's in working order (other than the connections or fuse). And finally, if the amp is bad, should I spend the extra time and money to send it to Alpine for out of warranty work, should I find a local establishment to repair it, or just bite the bullet and get a new amp?

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[Popwarhomie 5,000+ posts]

I have never had issues grounding multiple amps together. I would say it's the amp. Do you know anyone with another 4 channel that you can swap to be 100% sure?

 

[Greenleef]

I'm afraid I do not. Is there anything I can do to remedy it myself if it is Indeed shot?

 

[Greenleef]

I read that class d amps struggle with pulse modulation, though I didn't read enough to properly comprehend what that means for the speakers. Would ferrite or any other noise prevention components help? I know those are sort of taboo but I'm desperate.

 

[1aespinoza 10+ year member]

I know those are sort of taboo but I'm desperate.

Disconnect sub amp RCAs and turn system on. Is humming present? If not, connect your phone to the sub amp via 3.5mm to RCA cable. Play music. Is humming present? If no to both of those, amp is ok. Let us know the outcome.