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<blockquote data-quote="highfigh" data-source="post: 8883502" data-attributes="member: 691685">How did you set the input sensitivity controls (they aren&#039;t changing the gain- that&#039;s fixed and part of the original circuit design)?The manual shows &quot;For best performance, set the crossover knob to 200Hz (max). Set the gain to minimum, and slowly raise the gain. In general, an ideal gain setting ranges between the 9 to 10 O&#039; Clock position&quot;.Measure the voltage drop at each amplifier- if it&#039;s significant, I would start by looking at the ground cable from the body to the batteries- are they separated, or both in the same area?Add the fuses on each amp, then add the total, so you can post it- the manual for the PH-5000 shows &quot;FUSE RATING SHOULD BE NO LESS THAN 120 AMPERES&quot;, so the power cables (Positive AND ground) need to be able to handle this. If it&#039;s too small, the voltage WILL drop and you&#039;ll never develop the rated power AND the amplifiers will run hot.Corrosion on the ground connections will definitely cause this- clean all of them and measure the resistance/check voltage drop from each Positive power connection to the battery posts or side terminals. DO NOT use the terminals at the ends of the cables- ALL power connection measurements should be referenced to the battery terminals because it&#039;s possible to have significant resistance between the last terminal and the battery.I have worked with car audio since 1978- I have never heard of Class J, shown in the manual for the Earthquake amp- also, read the manual and look at the real output numbers- 5000W is peak power. [URL unfurl=&quot;true&quot;]https://en.wikipedia.org/wiki/Power_amplifier_classes[/URL]</blockquote>

[QUOTE="highfigh, post: 8883502, member: 691685"] How did you set the [I]input sensitivity controls [/I](they aren't changing the gain- that's fixed and part of the original circuit design)? The manual shows "For best performance, set the crossover knob to 200Hz (max). Set the gain to minimum, and slowly raise the gain. [B]In general, an ideal gain setting ranges between the 9 to 10 O' Clock position".[/B] Measure the voltage drop at each amplifier- if it's significant, I would start by looking at the ground cable from the body to the batteries- are they separated, or both in the same area? Add the fuses on each amp, then add the total, so you can post it- the manual for the PH-5000 shows "FUSE RATING SHOULD BE NO LESS THAN 120 AMPERES", so the power cables (Positive AND ground) need to be able to handle this. If it's too small, the voltage WILL drop and you'll never develop the rated power AND the amplifiers will run hot. Corrosion on the ground connections will definitely cause this- clean all of them and measure the resistance/check voltage drop from each Positive power connection to the battery posts or side terminals. DO NOT use the terminals at the ends of the cables- ALL power connection measurements should be referenced to the battery terminals because it's possible to have significant resistance between the last terminal and the battery. I have worked with car audio since 1978- I have never heard of Class J, shown in the manual for the Earthquake amp- also, read the manual and look at the real output numbers- 5000W is peak power. [URL unfurl="true"]https://en.wikipedia.org/wiki/Power_amplifier_classes[/URL] [/QUOTE]

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