Whine from AMP (NOT through speakers). HELP!

[phenryiv1 10+ year member]

I have a STRANGE issue with my Xtant 404m. I bought it from a member on here and had it shipped to me. A couple of weeks ago I powered it up (right after it arrived) to verify that it would work. All of the lights came on, so no issues. Because I was waiting on my sub to arrive, I pulled it back out.

Today, I had to go in to work late so I decided to install my sub. I powered up the amp again (no problems there) and had it all wired up to the sub with nothing on the front channels. When I turned on the HU, things were still fine and the sub sounded great. Now here is where it gets weird- the AMP makes noise...almost a whine or hum that seems to come from the power supply end. When I went to adjust the gains, it got really bad, and the sub made a LOT of crackling noise. When the amp was flat on the floor, the sound was really bad. When I sat it up and mountied it to the back of the seat, it got a bit better, but never entirely went away. What really sucks is that I plan to mount it horizontally when I do the permanent install.

I have not run the front channels yet, but with the rears bridged to the sub it is pretty bad. Could only running the amp with 2 chammels bridged (and no load on the other 2 channels) be the culprit?

Some background- 8 gauge pwr and gnd with a 30A fuse. I JUST ran my 4 gauge and have not attached it to the battery. The amp is recommended for a single 50A fuse. Could this be part of the problem?

Amp did this with the engine on or off.

Does anyone have any thought on what might be the problem?

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[helotaxi 5,000+ posts]

Fan? IIRC those amps are fan cooled and the fan speed is varied with the power output. There could be a problem with the fan itself acusing it to vibrate a bit and that vibration is being tranmitted to the surface that it is mounted to.

 

[phenryiv1 10+ year member]

Fan? IIRC those amps are fan cooled and the fan speed is varied with the power output. There could be a problem with the fan itself acusing it to vibrate a bit and that vibration is being tranmitted to the surface that it is mounted to.

HMMM...might be. Another thought was the PS itself vibrating against the board.

 

[helotaxi 5,000+ posts]

If there is no fan, there shouldn't be any moving parts in the amp to vibrate.

 

[thch 10+ year member]

inductors. transformers, and capacitors can all make noise. the SMPS usually operates above 20khz, making this a non issue.

still, damage to these parts, or issues with the power supply controller can cause issues.

I have an old amp that plays music without speakers! the output transformer has issues, and the wires move enough to make sound.

 

[NeedDirections 10+ year member]

I had that same problem with my planetaudio vx2200D It's the fan.