Rockford Power 400.4 slight draw

Dr Zeus · 26th January 2011, 04:35 AM

I came accross this punch amp, which looks to be in great shape and built in ~2000. Im wondering, why would Rockford have set the bias to 0.035v across the output's source resistors? Shouldnt it be more like 0.001 like I usually set Class AB amps to?

It was causing my 5A power supply to strain, and I could also hear the transformer coil squeel a bit on power-up.

Dr Zeus · 26th January 2011, 12:46 PM

Well the amp seems just fine with the source resistor voltage set to 0.001v. I also had to clean up one of the gain pots as it had a bad connection.

I'll have to check the rail voltage on this amp, but; I thought most of Rockford's 'Power' series amps used 640/9640s for outputs? This amp uses 540/9540s. Its like this amp is a Punch series with Power badging.

This amp is fixed btw.

Perry Babin · 26th January 2011, 06:09 PM

The 540s can handle more current so they're used when the rail voltage is low enough to do so. It has nothing to do with punch/power series.

26th January 2011, 04:35 AM	#1
Dr Zeus diyAudio Member Join Date: Oct 2010	Rockford Power 400.4 slight draw I came accross this punch amp, which looks to be in great shape and built in ~2000. Im wondering, why would Rockford have set the bias to 0.035v across the output's source resistors? Shouldnt it be more like 0.001 like I usually set Class AB amps to? It was causing my 5A power supply to strain, and I could also hear the transformer coil squeel a bit on power-up.

26th January 2011, 06:09 PM	#3
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	The 540s can handle more current so they're used when the rail voltage is low enough to do so. It has nothing to do with punch/power series. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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26th January 2011, 12:46 PM	#2
Dr Zeus diyAudio Member Join Date: Oct 2010	Well the amp seems just fine with the source resistor voltage set to 0.001v. I also had to clean up one of the gain pots as it had a bad connection. I'll have to check the rail voltage on this amp, but; I thought most of Rockford's 'Power' series amps used 640/9640s for outputs? This amp uses 540/9540s. Its like this amp is a Punch series with Power badging. This amp is fixed btw.

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