Amp Power Output, Price, and Differences:

If you are exploring adding an amplifier to your classic car, you may have noticed that there are a ton of different options, all at different price points, and many of them seem to put out the same amount of power.  This can be somewhat confusing, right?  Well, not all 400-watt amplifiers are the same.  Whether or not you hear a difference though is the big story. 400 watts is 400 watts as long as it is actually 400 watts.

For example, let's compare the Rockford Fosgate PBR400x4d, P400x4, T400x4ad, and T400-4. These are all 400-watt amps from Rockford Fosgate, one of the largest and most trusted brands in the industry. Every Rockford Fosgate amplifier comes with a birth certificate that will show the actual power output of the amplifier. 

Punch PBR400X4D

Rockford Fosgate Punch Mini 400W Amplifier

$279.99

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Punch P400X4

Rockford Fosgate Punch 400W Amplifier

$339.99

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Power T400XA4D

Rockford Fosgate Power Mini 400W Amplifier

$519.99

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Power T400-4

Rockford Fosgate Power 400W Amplifier

$399.99

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So which one is the best?  That all depends. Some of this depends on power output, some of it on the features, and some of it on marketing.

Power

Let's talk about power out first.  All are rated at 400 watts.  All things being equal, if the power output is held at 400 watts, they will all sound the same, with the exception of the T400x4ad.  The T400x4ad features a constant power circuit that ensures that the amp is constantly putting out 100 watts per channel, regardless of the speaker impedance.  As a speaker moves to generate sound, it's impedance is constantly changing.  It can go up to 8 ohms, it can go down to 1 ohm.  If you put a speaker on a meter, you will see the resistance change when you push on the cone.  That is the real difference and why sonically, it will sound better than the rest.

Features

Now, the other features.  All things being equal, if the power output is held at 400 watts, you probably will not be able to hear the difference.  So why the price differences?  This is going to come down to 4 main things

1. Warranty - The power amps come with a 2-year warranty, the Punch Amps come with a 1-year warranty, and Prime amps come with a 1-year warranty.  If you purchase a Rockford Fosgate amp wiring kit, that warranty is extended for an extra year with Power and Punch bringing it to 3 years and 2 years respectively
2. Thermal Management and the Amount of Aluminum - The Power amp has more aluminum for thermal management than the Punch, which has more Aluminum than the Prime, etc.  During testing, the Prime will cut out to thermally protect itself before the Punch which will cut out before the Power.  Why is this important?  If you listen to your music full blast and essentially floor the amp the entire time, it is going to generate more heat.  You don't want your amp to constantly cut out because it is protecting itself because it turns your music off and it is annoying.  
3. Onboard Features - The PBR400x4d and the T400x4ad all come with the CLEAN setup.  This uses LED lights to indicate both a clipped input and a clipped output signal.  This allows you to determine where your source unit is distorting on the input so you know what volume to not turn it past.  It also, allows you to set the gain on the output so that the speaker or subwoofer does not get a clipped signal.  Clipping leads to distortion which then blows your speakers.
4. Signal Processing - 12db crossovers versus 24 dB crossovers.  The higher the number, the steeper the crossover slope is.  This allows for finer tuning of your crossover points so that you can more accurately dial in, which speakers are reproducing the signal.

Marketing

Now the marketing aspect.  Above you can see that there are 4 different 400-watt amplifiers and they all have a different power output.  Why is a Punch P400x4 a 400-watt amp when it is actually putting out 500 watts?  The answer is two-fold.  First, Rockford Fosgate wants to make sure they under-promise and over-deliver.  If you buy a 400-watt amp and it turns out it is only putting out 380 watts, you're going to be upset, angry, and feel like you've been ripped off.  The second part comes down to the public and consumers.  The most searched 4 channel amplifier is a 400-watt amp.  Most speakers can handle somewhere between 50-100 watts RMS and this fits right in the sweet spot of a 400-watt amp.  If they said it is a 730-watt amp, there aren't that many 730 watt amplifiers out there and when you go searching for a 4 channel, 400-watt amp, their product is not going to show up.

Hopefully, this clears things up.  Size, ease of installation, gain setting, actual power output, and sound quality will ultimately determine which amp is best for you.  We are definitely partial to the T400x4ad due to the constant power circuit.  With an amp that small with that kind of technology and output, it is easy to justify the extra cost because it just outperforms the other amps from Rockford Fosgate.