Need help with amp
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Joined: Jul 2010
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c230k
Need help with amp
Hi Everyone -
I have an aftermarket 250 watt DD audio sub in my 03 C230 and it usually works great. It's connected with an elf audio amp to my Pioneer double din and the amp is hooked up directly to the battery by 4 gauge wire. Usually it works great and is loud, but recently it only plays and about half volume and then randomly gets loud (usually when on the highway, or after running the car without the radio on for a while).
Anyone know why the amp is doing this - it seems starved for power but it's only a 250 watt system so I don't think this should be the case. I know capacitors are usually not needed, but would one or a big 3 upgrade help out? My battery rests at 12.6v when car is off and is showing about 13.4 when running.
Thanks so much for your help!
Tim
I have an aftermarket 250 watt DD audio sub in my 03 C230 and it usually works great. It's connected with an elf audio amp to my Pioneer double din and the amp is hooked up directly to the battery by 4 gauge wire. Usually it works great and is loud, but recently it only plays and about half volume and then randomly gets loud (usually when on the highway, or after running the car without the radio on for a while).
Anyone know why the amp is doing this - it seems starved for power but it's only a 250 watt system so I don't think this should be the case. I know capacitors are usually not needed, but would one or a big 3 upgrade help out? My battery rests at 12.6v when car is off and is showing about 13.4 when running.
Thanks so much for your help!
Tim
Super Member
Joined: Mar 2012
Posts: 968
Likes: 62
From: San Francisco, CA
2005 c230SS
My Alpine MRX-V60 seems like it does something similar, i.e. lowering the output volume when it gets warm. I remember reading somewhere that this my be a protection mechanism in the amps?
Hopefully someone out there can shed more light on this ...
Hopefully someone out there can shed more light on this ...
MBWorld Fanatic!
Joined: Jan 2005
Posts: 2,848
Likes: 15
From: Orange County
2005 C Wagon (No snickering please!)
Let's start with the choice of wire. 4 Gauge wire without insulation is .204". Wired in a chassis that is good for 135 amps. If your amplifier drew 10 amps I would be shocked. I doubt the designer provided a power terminal to mechanically support that large a wire. Without proper dressing and support of that large a cable I would suspect a crack at or near the power input to the amp caused by normal vibration. Usually it is a crack in the solder. With a little heat it might make better contact and sound normal.
In W203 cars there is an 8 gauge wire already in the trunk. A fuse can be added to an unused slot on the rear SAM and then wired to run any amp that can drive the speakers at a level that will allow you to stay in the car. 14 to 18 gauge is plenty.
The usual rules of good practice require good ground connection, usually an existing stud works well.
There are also thermal considerations. These tend to be class D amps which run cooler because they use switched transistors, but they have awful distortion and poor linearity compared to well designed class AB amps. I might use a class D amp for LFE or a subwoofer, but never for HiFi audio. The class D amps are cheaper to make, and often have poor thermal performance. While they are switching amps, complex sound waves force some transistors to operate in a linear manner and the heat quickly goes through the roof. Mounting of the AMP is critical to get good airflow over the heat sink. If you park in the sun, the AMP might already be at 140 degrees when you open the door. In this case, don't switch on the AMP until the A/C has time to work. Rather than the trunk, consider under the seat, there is A/C there.
Your battery voltage is fine. A capacitor would be as useful as teats on a boar hog.
In W203 cars there is an 8 gauge wire already in the trunk. A fuse can be added to an unused slot on the rear SAM and then wired to run any amp that can drive the speakers at a level that will allow you to stay in the car. 14 to 18 gauge is plenty.
The usual rules of good practice require good ground connection, usually an existing stud works well.
There are also thermal considerations. These tend to be class D amps which run cooler because they use switched transistors, but they have awful distortion and poor linearity compared to well designed class AB amps. I might use a class D amp for LFE or a subwoofer, but never for HiFi audio. The class D amps are cheaper to make, and often have poor thermal performance. While they are switching amps, complex sound waves force some transistors to operate in a linear manner and the heat quickly goes through the roof. Mounting of the AMP is critical to get good airflow over the heat sink. If you park in the sun, the AMP might already be at 140 degrees when you open the door. In this case, don't switch on the AMP until the A/C has time to work. Rather than the trunk, consider under the seat, there is A/C there.
Your battery voltage is fine. A capacitor would be as useful as teats on a boar hog.
Last edited by Moviela; Oct 30, 2013 at 04:13 AM.
Thread Starter
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Joined: Jul 2010
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c230k
Let's start with the choice of wire. 4 Gauge wire without insulation is .204". Wired in a chassis that is good for 135 amps. If your amplifier drew 10 amps I would be shocked. I doubt the designer provided a power terminal to mechanically support that large a wire. Without proper dressing and support of that large a cable I would suspect a crack at or near the power input to the amp caused by normal vibration. Usually it is a crack in the solder. With a little heat it might make better contact and sound normal.
In W203 cars there is an 8 gauge wire already in the trunk. A fuse can be added to an unused slot on the rear SAM and then wired to run any amp that can drive the speakers at a level that will allow you to stay in the car. 14 to 18 gauge is plenty.
The usual rules of good practice require good ground connection, usually an existing stud works well.
There are also thermal considerations. These tend to be class D amps which run cooler because they use switched transistors, but they have awful distortion and poor linearity compared to well designed class AB amps. I might use a class D amp for LFE or a subwoofer, but never for HiFi audio. The class D amps are cheaper to make, and often have poor thermal performance. While they are switching amps, complex sound waves force some transistors to operate in a linear manner and the heat quickly goes through the roof. Mounting of the AMP is critical to get good airflow over the heat sink. If you park in the sun, the AMP might already be at 140 degrees when you open the door. In this case, don't switch on the AMP until the A/C has time to work. Rather than the trunk, consider under the seat, there is A/C there.
Your battery voltage is fine. A capacitor would be as useful as teats on a boar hog.
In W203 cars there is an 8 gauge wire already in the trunk. A fuse can be added to an unused slot on the rear SAM and then wired to run any amp that can drive the speakers at a level that will allow you to stay in the car. 14 to 18 gauge is plenty.
The usual rules of good practice require good ground connection, usually an existing stud works well.
There are also thermal considerations. These tend to be class D amps which run cooler because they use switched transistors, but they have awful distortion and poor linearity compared to well designed class AB amps. I might use a class D amp for LFE or a subwoofer, but never for HiFi audio. The class D amps are cheaper to make, and often have poor thermal performance. While they are switching amps, complex sound waves force some transistors to operate in a linear manner and the heat quickly goes through the roof. Mounting of the AMP is critical to get good airflow over the heat sink. If you park in the sun, the AMP might already be at 140 degrees when you open the door. In this case, don't switch on the AMP until the A/C has time to work. Rather than the trunk, consider under the seat, there is A/C there.
Your battery voltage is fine. A capacitor would be as useful as teats on a boar hog.
Thanks again for your help,
Tim
Super Member
Joined: Mar 2012
Posts: 968
Likes: 62
From: San Francisco, CA
2005 c230SS
You sure your battery isn't going out? I see many strange things happen when a battery is at the end of it's life ... inability to hold voltage when carrying a strong current -- or inability to carry a current for an extended period of time. I would say have your battery checked, and if it's convenient to test the radio out with another battery in the car, do that.
Thread Starter
Member
Joined: Jul 2010
Posts: 85
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c230k
You sure your battery isn't going out? I see many strange things happen when a battery is at the end of it's life ... inability to hold voltage when carrying a strong current -- or inability to carry a current for an extended period of time. I would say have your battery checked, and if it's convenient to test the radio out with another battery in the car, do that.
