Bet you haven't seen this amp problem

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ozsir2
ozsir2's picture
Bet you haven't seen this amp problem

I have searched numerous forums and am wondering if anyone here knows what's going on.

I replaced a new head unit to my system and reset the gain on my Alpine mrv-t402 (2 channel amp). Now when I turn on my stereo when it is at low volume there is crackle from the left speaker channel - which disappears when the volume is turned up...but also does not return once I turn volume back down. It is only after the system "has cooled down" when I notice crackle again.

I have checked to make sure it's not the speakers (switching the L/R spkr outputs from the amps results in crackle in the right channel), and not the head unit (switching the RCA inputs to the amp - there is still crackle from the left channel). Turning the gain pot when music is playing does not affect the crackle so I don't think it is "dust" in the pot.

Any advice besides "take it to a professional" would be greatly appreciated.

Larry Dillon
Larry Dillon's picture
If the amp has a speaker or

If the amp has a speaker or protection relay or a solid state switching to switch off the speakers, or it is a ground loop somewhere in the setup, my notes shows of a problem with the same complaint on a differant type of amp, and it turned out to be a problem in the feedback circuit.  Those are very hard to find sometimes.  If it is a ground loop problem you can try this.  When the noise is there try running a wire from where the head unit is grounded to the same place where the amp is grounded.  If it is not a ground loop problem, your going to need to look at a circuit diagram to see how the speakers are coupled to the amp internally.  Good luck and let us know if you find anything

ozsir2
ozsir2's picture
Thanks for the tip. I'll give

Thanks for the tip. I'll give it a go. I'm wondering why this problem is appearing now when it wasn't present with my previous head unit. So a ground loop is where there is a difference between the ground of the head unit compared to the ground of the amp?

ozsir2
ozsir2's picture
Since my last post more weird

Since my last post more weird things have happened. The crackle briefly moved to both speakers, then to the right speaker with the left being totally fine. Now there is no crackle in the right speaker...however the power output substantially less than the other side. The power output does increase with an increase in the head unit volume control and also the increase in the amp's gain control....but it is still faint compared to the other speaker. I have swapped around the RCAs as well as the seaker outputs to confirm the problem lies in the amp. Any other comments would be greatly appreciated.

Larry Dillon
Larry Dillon's picture
No not really, its an amp

No not really, its an amp problem and these amps have no user replaceable parts inside.

ozsir2
ozsir2's picture
Ok thanks for the help.

Ok thanks for the help. Bloody amps...this is the second one that has blown up on me.

Larry Dillon
Larry Dillon's picture
Make sure you do a tone test

Make sure you do a tone test or have the input level set not to exceed the total amount of input volts the amp has as alimit and between a certain frequency range. You may be overloading the input and that would certainly overdrive the outputs stage of the AMP. I have seen this problem a hundred times!

 

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