Amp Volume Fluctuations

Gewehrschuss · 06-17-2005, 01:16 PM

I have my Carputer running directly through an amp powering the speakers (no head unit) and when I drive, the volume decreases when I step on the gas or brake pedals.

I tried disconnecting the computer and using a standalone MP3 player as a sound source for the amp and it still did the same thing, so it shouldn't have anything to do with the computer. I also regroudned it, but it didn't help.

The amp is 60 W x 4 and the alternator is 90 amps. The carputer has a 90W AC power supply fed by a 150 W RMS inverter.

I'm out of ideas and I'd be very appreciative of some suggestions!

scott_fx · 06-17-2005, 01:23 PM

when you are driving you are probably around 14.4v when you are idling it'll drop between 12-13v so thats why the volume is going down. how new is your battery?

one option is to get a louder exhaust, that way it'll sound louder at idle

Gewehrschuss · 06-17-2005, 01:35 PM

my battery is a couple of years old. I hooked a voltmeter up to the power leads to the amp and the voltage does fluctuate when idling if I turn on the headlights or AC, could that be the cause? If so, how can I fix that... other than muffling it out with a loud exhaust?

Moondog51 · 06-17-2005, 02:04 PM

Quote: Originally Posted by Gewehrschuss

my battery is a couple of years old. I hooked a voltmeter up to the power leads to the amp and the voltage does fluctuate when idling if I turn on the headlights or AC, could that be the cause? If so, how can I fix that... other than muffling it out with a loud exhaust?

I believe the traditional fix for this is to add a stiffening capacitor for the amp.
Ive never used one myself though.

scott_fx · 06-17-2005, 02:08 PM

A cap wont solve that, they don't have the staying power, they are only used for quick bursts like a bass hit. I'm not sure exactly how to solve it, maybe an optima yellow top? what gauge wire are you using? do your headlights dim when the bass hits?

Gewehrschuss · 06-17-2005, 02:30 PM

I'm using 10-gauge wire

Gewehrschuss · 06-17-2005, 02:31 PM

no, my headlights don't dim at all

scott_fx · 06-17-2005, 02:36 PM

the wire may be too thin, it may be adding too much resistance into the system. maybe you could try a quick test by running some 4 gauge instead. a quick test may be to just get some 8 gauge wire and wire it in parrallel (doesn't have to be hidden, just run it on the outside for this test) to the 10 gauge that you have. keep your revs high and listen to the radio then let it idle and see if the volume goes down.

Gewehrschuss · 06-17-2005, 02:40 PM

I'll give it a try, thanks for the suggestion

scott_fx · 06-17-2005, 02:47 PM

keep us posted if it doesnt work, we'll get down to the bottom of this. there are a few pro installers on this forum that may chime in with some other advice

ralphyboy1 · 06-17-2005, 04:33 PM

Quote: Originally Posted by scott_fx

the wire may be too thin, it may be adding too much resistance into the system. maybe you could try a quick test by running some 4 gauge instead. a quick test may be to just get some 8 gauge wire and wire it in parrallel (doesn't have to be hidden, just run it on the outside for this test) to the 10 gauge that you have. keep your revs high and listen to the radio then let it idle and see if the volume goes down.

I'd bet there is two issues, the first one could be too small of guage wire and the second one could be an older battery. The above test is the perfect starting point. Like already was said let us know.

TimW · 06-18-2005, 12:37 AM

To start with, the battery isnt supplying the power when youre driving. The alternator is where the juice is coming from.. So dont go replacing parts until you do some basics first.

Id suggest upgrading all your wiring first, then seeing how it performs, then consider upgrading the alternator. (90ams should be plenty for a small system though)...

At least 8 guage to the amp/computer, upgrade the battery to chassis ground, upgrade the engine to chassis ground, upgrade the alternator to battery power cable.

scott_fx · 06-18-2005, 01:40 AM

i totally agree with both of you....check the wiring first

ralphyboy1 · 06-18-2005, 03:56 AM

Quote: Originally Posted by TimW

To start with, the battery isnt supplying the power when youre driving. The alternator is where the juice is coming from.. So dont go replacing parts until you do some basics first.

Id suggest upgrading all your wiring first, then seeing how it performs, then consider upgrading the alternator. (90ams should be plenty for a small system though)...

At least 8 guage to the amp/computer, upgrade the battery to chassis ground, upgrade the engine to chassis ground, upgrade the alternator to battery power cable.

Before you try to make me sound like an idiot you may want to realize that if the battery is bad it will not let the alternator do it's job properly. A good battery and a good alternator are both good ideas but you should ALWAYS swap in a good battery first(after getting the wiring right). Now you may tell me I'm wrong.

scott_fx · 06-18-2005, 03:59 AM

i think you're correct

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