Jason Garrett

Question about Power Supplies

Being the destitute home theater nut I was thinking about using some car audio equipment that I had sitting around for a makeshift amp and sub just to see how it would sound. (I wasn't overly impressed with the Velodyne CHT-12 that is within my budget).

I quickly found the info that a car battery recharger doesn't work and that you need a regulated and filtered dc power supply. Well, my amp (Orion HCCA 225 - around 500 watts) can draw at the very least 30 amps peak. The power supplies I saw that supply that are like $200 http://www.sacramentoelectronics.com...directory.html Are there power supplies that will improvise for less? I'm not shelling out bills to test this out, but I'm curious.

Now, I wonder do home amps/receivers use dc current amps and how do they manage if regulated and filtered power supplies are so expensive? I own one of the newer Onkyo's and I didn't know about the power supply issues with them until after the purchase. I wasn't aware of just what role the power supply played until my research for my little idea.

Dave Milne

Jason,
As you have found, car amps aren't cost-effective for home use because of the power supply required.

The fundamental problem here is that the final stage of a power amplifier requires two symmetrical DC power supply rails --typically +/- 50V or so depending on power rating. Home amps create this by transforming, rectifying, and filtering the AC wall power. Car amps create this by first switching the DC input to AC (typically high frequency - 100KHz) and then transforming/rectifying/filtering just like a home amp (although much easier because of the high frequency).

Using a car amp at home means that you must transform/rectify/filter the 110Vac to 12Vdc (with a power supply) then switch the DC to high-frequency AC (in the car amp's power supply section) and finally transform/rectify/filter the AC to +/- 50V DC. That's a lot of power converting!

The HCCA-225 is rated at 25W x 2. However, it can drive very low impedances so it may be capable of maybe 200 watts peak output. This could equate to 500 watts total input, taking into account the efficiencies of the amplifier (50% at best) and switch-mode power supply (around 90%). 500 watts is about 42A at 12V. So you might need the 50A version of the power supplies you linked to. $250 for a 50A regulated supply is actually quite cheap.

You don't really need a regulated supply, though... the power in a car is far from regulated. Battery chargers won't work because they're typically unfiltered... but a decently filtered unregulated supply should be fine. It will still be expensive --500VA, 60Hz transformers are a big pile of iron and copper, and 10,000 uF or larger 100V filter capacitors aren't cheap either --but maybe around $150 instead of $250.

Bottom line... forget the car stuff and buy a cheap home amp or prosound amp from Audiogon or Ebay

Allen Ross

CROWN

I don't think you can beat a nice DC 300A for around 220 bucks

Member and Founder of the \"Its Never to Big or too Loud to have in a Dorm Club\"
Everyone in college should have a 9 cuft Tempest in their closest!

Jason Garrett

Thanks for taking the time to reply Dave. I was out checking what stuff I had to sell on e-bay and the car battery charger got me to thinking what it would take to rig my old car stuff up and see how it would sound compared to what I had been out listening to at the home audio stores.

I thought the Sunfire subs sounded incredible (2 10" in a really small box - way out of my budget) but I wasn't too impressed with the Velodyne cht-12 (maybe just a bad setup). I had a box with 2 Orion 10 inch dual 4 ohm voice coil woofers that paired up nice with that 225 HCCA (rated by Orion as 400 watts @ 1ohm). Anyway, just as well - cutting the box open I found one voice coil had lost it's connection. All those years with that box only putting out 3/4 of it's potential (if not less having to drag the 2nd voice coil's dead weight).

Thanks again.