wierd noise

Kinetic

guys i recently try to bridge the PDX-4.100
so instead of having 4x100, now i have 2x200.

so i adjust the gain to have 100 RMS per channel, but without distorsion.


i bridged as i read in crutchfield:
http://www.crutchfield.com/App/Product/Item/Main.aspx?i=500PDX4150&search=4.150&tp=115&tab=review

So I put the positives on the odd numbered channels 1 and 3 with their respective negatives on the even numbered channels 2 and 4.

sounds a lot better, but there is a little wierd noise, when i turn on the HU, its like interference, or like the old computer fax-modems.

if I turn the volume up to 15 the noise goes away and the music starts, after that i can listen the HU at any volume level, the noise only appears, when i just turn the HU on.

I already check:

the IC on the HU
the ground on the AMP
try with different GAINS
the speakers conections
the RCA (each one)


what else can it be?

zingo

Hmmm... could it be electrical interference? Are you running the RCA cables and power wire on opposite sides of the car?

ShinAce

Does the noise stay constant or go up with volume?

Kinetic

zingo wrote: »

Hmmm... could it be electrical interference? Are you running the RCA cables and power wire on opposite sides of the car?

yes I have the rcas and speakers wires on the right side

the power wires on the left side

Kinetic

ShinAce wrote: »

Does the noise stay constant or go up with volume?

its constant, and when i turn up the volume up to 15 (aprox) the noise goes away, and then i can have the volume from 0 to 35 without noise.

when the noise is on, theres no music.

i will try to put a video

ShinAce

Really!

Let me get this straight. You turn the volume down when you turn the car off. Now when you get back in and start it up, constant noise. The noise dissapears once the volume goes above 15, even if you back it down after.

I would look for alternator noise, but I can't understand why it would disappear.

One more question, does reving the engine change the noise at all?

Kinetic

ShinAce wrote: »

Really!

Let me get this straight. You turn the volume down when you turn the car off. Now when you get back in and start it up, constant noise. The noise dissapears once the volume goes above 15, even if you back it down after.

Yes thats right

ShinAce wrote: »

I would look for alternator noise, but I can't understand why it would disappear.

yeah me too

ShinAce wrote: »

One more question, does reving the engine change the noise at all?

no, when i rev it, sounds the same

ShinAce

Check the wiring on the amp. Loosen and retighten if possible.

Next step would be to swap the amp temporarily. If that works, mess with the amp. You could try hooking it up with a cd player and small battery in house.

Kinetic

ShinAce wrote: »

Check the wiring on the amp. Loosen and retighten if possible.

Next step would be to swap the amp temporarily. If that works, mess with the amp. You could try hooking it up with a cd player and small battery in house.

cool i will do that

thanks a lot

Kinetic

a guy on the caraudio forum told me that this is a normal mistake on all the PDX amps when you bridge them.

and theres nothing i can do.

what do you think?

ShinAce

My guess is that there is some kind if biasing issue with the amp. This is not something you should even consider fixing.

Depending on the type of circuit used, and how it bridges, he could be right. I personally doubt a company would advertise the amp as bridgeable without having successfully done it themselves.

Kinetic

ShinAce wrote: »

My guess is that there is some kind if biasing issue with the amp. This is not something you should even consider fixing.

Depending on the type of circuit used, and how it bridges, he could be right. I personally doubt a company would advertise the amp as bridgeable without having successfully done it themselves.

thats what i thought about a brand name as Alpine, but i try to talk to Alpine of Mexico and they are so incompetent, the dont have any information.