The reason we typically don’t recommend car amps to people inquiring about them is because an adequate power supply will cost more than just buying a comparably-rated AC-powered amplifier.
For instance, the 200 watt @ 4-ohms Yamaha amp I used to have in my car had two 30-amp fuses, so it would require a 60-amp power supply for the amp to be driven to its maximum output.
In addition, the amp will only be as “clean” as its power supply (i.e. pure DC voltage free of any AC artifacts).
If you’ve managed to economically overcome these daunting obstacles, maybe you can share with us how you did it?
Regards,
Wayne A. Pflughaupt
You make good points and I agree with you.
I 'think' that the power provided to my amp is pretty clean though.
I know its kind of a crude instrument for the task, but my Fluke 77 Series II measures 0.000Vrms AC on the 12V rail. Before I removed the 120mm fan from the PSU, I was measuring notable ripple-- I don't recall but I think 0.020Vrms AC.
I am open to any comments or criticism. I am genuinely interested in how well this system works and how it compares to home receivers, power amps, and integrated amplifiers in similar power ranges.
What I did was the following:
1. Bought the Corsair HX-1000W PSU.
2. Disconnected and removed the internal 120mm fan.
3. Shorted the green wire on the ATX power connector to ground (this powers the unit on.)
4. Took all the PSU's modular cables that have 12V pins and Ground pins and soldered all the 12V wires to a piece of 4 AWG power wire and all the Ground wires to a piece of 4 AWG power wire.
5. Ran the 4 AWG power wires to a 1 Farad electrolytic capacitor.
6. Ran short (4-5") 4 AWG power wire to the amplifier from the capacitor.
7. Hooked up amplifier to speakers and RCA interconnects.
Interestingly, the PSU is actually powerful enough to fully charge the capacitor (without going into overcurrent protection (maybe undervoltage protection)) without having to charge up the capacitor to 12V first.
I wish I could give you guys some scope readings under various loads, but I don't have access to a scope.
I am always getting 0.000Vrms AC though, so that is a good sign.
I am making some loose assumptions about the setup.
1. Car audio amplifiers should have good noise rejection to cope with the noisy car environment. Even my DMM shows some nasty AC voltage with the car running.
2. Computer PSUs generally provide "fairly" clean power considering their high current output to cope with the sensitive nature of computer electronics. Hopefully the switching frequency (50 KHz to 60 KHz I would think) would be inaudible anyways.
3. Good car audio amplifiers should have robust output stages because they need to be 4ohm stable. My amplifier is rated at 450W per channel @ 2ohms @ 1% THD. This may help better drive speakers with poor impedance characteristics.
4. Keeping the power supply away from the amplifier stage should help reduce EMI/RFI. I don't know enough about amplifier internals to really make this assertion. I assume decent home amplifiers take this into consideration.
5. The massive 1 Farad capacitor I hooked up should provide at least some AC noise rejection. Admittedly, the cap's value is probably over-sized and I expect the system may perform as well or better without the cap.
My amp is $900 retail, so it better sound decent! I was able to pick it up for much less though. The power supply I purchased was over $200, so I have sunk about $550 into this amp and PSU combo. That certainly gets me into throwing range of some nice stereo receivers. In particular, I'm wondering how the Harman Kardon 3490 ($279 authorized including shipping) would sound. I could have bought two of those for the same amount of money. But then I lose my high-pass filter for the bookshelf speakers...
Lastly, I am using a Furman PM-8 Series II line conditioner on all my computer equipment. I grounded that particular AC outlet to the well.
