PeachParts Mercedes-Benz Forum - View Single Post - amp keeps turning off, and sub gets trebble!

G-Benz · #2 06-26-2002, 04:18 PM

Does the amp have a built-in crossover? There is really no such animal as a "sub" amp, just an amp with the crossover points optimized for bass frequencies and below.

Multi-channel amps usually have speaker outputs for a sub, but the built-in crossover filters out the upper frequencies, and there is usually a dial for additional tailoring of the frequency rolloff point for your sub(s).

Running the amp at low ohms to gain power is a pretty old trick (back in the CAN days when I competed, before IASCA was born). We used to do this so that we could compete in the 0-50 watt classes and really be pushing 300 watts!!! Needless to say, the amps had a short life!

Expensive well-designed amps can be designed to withstand 1-ohm loads and operate safely under those conditions. The tradeoff is heat and power. Your amp may be demanding an amp load (900 watts at 1-ohm) that your car's electronics cannot provide, so it shuts down in protection mode. It's no secret that competition vehicles usually come equipped with 200-amp alternators...I've even seen some with dual alternators!

Another solution is to use big storage capacitors...these are pretty mainstream now. Their job is to store up the unused voltage (which the way your amp probably operates 70-80% of the time) for the instance you have a demanding signal that requires more than usual power.

Check your power wires to the amp as well. If it's too warm after a lively stereo performance, then your wire gauge is too small. Think of wires as water pipes...you can't get Hoover Dam flow out of household pipes!

For 900 watts, I would go no smaller than 8-gauge. Many competitors use zero-gauge wire (which is used on professional welding equipment), but it takes Hercules to bend into desired positions.

Bottom line: if you are getting high frequencies in your sub, then you probably lack a crossover. That is your first necessary purchase.

I think 900 watts is a bit excessive for anything but dB competition vehicles (but I'm getting old).
You might have to drop down to the paltry 300-400 watts your amp is spec'ed to provide.