Are A/B amps less prone to "dirty power"

scottatl · Aug 31, 2023

I have been hunting down a hum, I assumed it was a ground loop but who the hell knows? I have tried many, many fixes. The last one I switched out my 4-channel D amp with an old 2-channel A/B and - - poof the hum is gone.

Infinity Reference 3004A 70W x 4 vs an older Kicker.

My Infinity is under warranty so I am sending it back and seeing if it is a bad amp. I don't think that is the issue because I ran the system with direct battery power and the car was completely off (including ignition) and I did not get a hum, it is infuriating. Could be that Infinity is just a more sensitive unit so swapping out will not help.

I wish there was a power conditioner that I could put in between the battery and amp, but as far as I can tell one does not exist. The capacitors on the market are for surge not to clean the power.

Hanatsu · Aug 31, 2023

Class D amps do have that PWM switching noise. Most of it should be filtered out by the the large inductor inside the amp. If there's an audible hum on the output of the amp without something connected at the input I'd bet something is faulty inside that amp.

251699 · Aug 31, 2023

For sure class A/B are more forgiving of noise but it can still happen obviously. Sounds like your test was a good one, and answered the question. Thanks for sharing

Jroo · Aug 31, 2023

I would guess bad amp vs just being class D. I know a lot of people that switched to class D from cheaper to more expensive amps and none call out any perceived SQ or noise changes by doing so. I cant happen, but I think that just has more to do with the amp and maker vs being class D.

mumbles · Aug 31, 2023

If you have the ability to hook the amp/speakers up outside of the car, say on a workbench, you could see if it still hums... if so, probably a bad amp, if not might be install related.

Are A/B amps less prone to "dirty power"

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