You are not logged in. [Log In]


Forums » General Discussion » Technical Questions » Quick question for the car stereo guys...

Topic Options
Rate This Topic
#156540 - 01/22/07 02:17 AM Quick question for the car stereo guys...
BrenR Offline
connoisseur

Registered: 12/10/03
Posts: 3602
Loc: Winnipeg MB Canada
Hello, car stereo types...

So, I've mentioned before, I've got Delco 4-ohm 6x9s in the garage for speakers... they used to be powered by a Sony home boombox-type thing that I hacked up a new amp circuit into... the CD-player was on it's way out when I moved it out there, and has since completely given up the ghost.

I decided to replace it with a cheap car head unit. My question is - how to power it. I originally had plans to use a 12v 3A (I believe - I think it's still at my parents') power supply I snagged out of a vending machine years ago. Reading the manual that came with the unit, it lists supply voltage as 14.4V, max 15A current consumption. So what is the best way to power a car head unit from "shore power"... that 12V 3A supply? I notice Princess Auto has a 15V, 2.4A wall wart type... I'm prefering to stay away from the high-end HAM radio type stuff if possible... and the same with messing around with an automotive battery to power it... that's just too much hassle for what it's worth.

How much current will a head unit really require if not pushed like crazy... 15A seems awfully high - my battery charger is switchable 2A/6A... 2.5x it's peak current output seems a bit much, no?

Any insight would be appreciated. Car audio is not my forte.

Bren R.

Top
#156541 - 01/22/07 03:08 AM Re: Quick question for the car stereo guys... [Re: BrenR]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10415
Loc: Calgary, Alberta
Most of the Head units have a seperate inline fuse of only 2-5 amps. I would bet as long as you are not working it hard your vending machine unit will do the trick nicely. I built my own 12V PS and I have used it many times to help diagnose some electronic issues on cars as well as drive car stereos in my house. it only has 5Amp out put.
_________________________
Jason
-----------------
TTTHHHPPPPPTTTT!

My HT

Top
#156542 - 01/22/07 01:52 PM Re: Quick question for the car stereo guys... [Re: jakewash]
Haoleb Offline
connoisseur

Registered: 09/25/02
Posts: 1488
Loc: Maine
you could pick up an old computer power supply and use that. Most of them of decent size (300w+) put out over 10a on the +12v line.


Edited by Haoleb (01/22/07 01:53 PM)
_________________________
Haoleb's Audio/DIY Website

Top
#156543 - 01/22/07 02:04 PM Re: Quick question for the car stereo guys... [Re: jakewash]
BrenR Offline
connoisseur

Registered: 12/10/03
Posts: 3602
Loc: Winnipeg MB Canada
Oddly, this one has a plastic fuse box on the channel saver (constant power) and switched power lines... with a 1A fuse on the constant power wire and a 15(!!!)amp fuse on the power wire.

Just for poops and giggles, I hooked it up to a pair of 6x9s and hooked up the ammeter, and it seemed to stay at a steady 1.4A draw no matter what I did... cranked it up, flipped the bass setting to +10. So I think I'll be okay.

Was just thrown for a loop by the Engrish instruction manual suggesting a 15A max draw... but in hindsight, since the radio fuse in a car is usually shared on a 15A or alone on a 7.5A or so, that seemed kind of odd... but better to ask those who mess around with these things more than I.

Bren R.

Top
#156544 - 01/22/07 02:14 PM Re: Quick question for the car stereo guys... [Re: Haoleb]
BrenR Offline
connoisseur

Registered: 12/10/03
Posts: 3602
Loc: Winnipeg MB Canada
Quote:

you could pick up an old computer power supply and use that. Most of them of decent size (300w+) put out over 10a on the +12v line.


I save old AT power supplies (since they're a bit easier to repurpose than ATX - no "power good" line to hold to ground)... but I've found that they don't regulate without a fairly substantial load. I use one in my arcade cabinet to run the coin reject lamps and cooling fans, and that's just enough draw for the supply (150W AT) to regulate. If you ever test a PS without a load, you get weird unregulated power - like 5v - 48v swings on the 12V side and 2v - 20-ish volt swings on the 5V side.

That was another idea I was thinking of... just worried that if the head unit isn't on before the PS (and how could it be?) that the PS would chuck some wonky, unregulated voltage at it. Of course, if voltage sensitive computer equipment isn't affected... a less finicky $60 head unit shouldn't be, either.

Bren R.

Top
#156545 - 01/22/07 04:19 PM Re: Quick question for the car stereo guys... [Re: BrenR]
Haoleb Offline
connoisseur

Registered: 09/25/02
Posts: 1488
Loc: Maine
Quote:

Quote:

you could pick up an old computer power supply and use that. Most of them of decent size (300w+) put out over 10a on the +12v line.


I save old AT power supplies (since they're a bit easier to repurpose than ATX - no "power good" line to hold to ground)... but I've found that they don't regulate without a fairly substantial load. I use one in my arcade cabinet to run the coin reject lamps and cooling fans, and that's just enough draw for the supply (150W AT) to regulate. If you ever test a PS without a load, you get weird unregulated power - like 5v - 48v swings on the 12V side and 2v - 20-ish volt swings on the 5V side.

That was another idea I was thinking of... just worried that if the head unit isn't on before the PS (and how could it be?) that the PS would chuck some wonky, unregulated voltage at it. Of course, if voltage sensitive computer equipment isn't affected... a less finicky $60 head unit shouldn't be, either.

Bren R.




Perhaps thats something to do with the specific supply's regulation. I have 5 or 6 old ATX supplys and none of them have ever measured more than a volt off the proper voltage with no load. Thats the whole point of having a regulated PS!
_________________________
Haoleb's Audio/DIY Website

Top
#156546 - 01/22/07 05:00 PM Re: Quick question for the car stereo guys... [Re: Haoleb]
BrenR Offline
connoisseur

Registered: 12/10/03
Posts: 3602
Loc: Winnipeg MB Canada
It only happens with switched-mode AT supplies... I don't think any ATX supply requires a minimum load.

I can't bring myself to use an ATX... they could still have a life inside a box as a backup in case a PS dies.

But yes, you're right... most/all ATX don't have the same issue.

Bren R.

Top
#156547 - 01/22/07 05:21 PM Re: Quick question for the car stereo guys... [Re: BrenR]
BrenR Offline
connoisseur

Registered: 12/10/03
Posts: 3602
Loc: Winnipeg MB Canada
Picked up the 12V supply from my parents' this afternoon. It works. Noise floor is a bit high when the amp circuit is in, but it's definately "good enough" for the garage.

The LCD screen looks like Mardi Gras, but... that just adds to the charm I think.

Bren R.

Top

Moderator:  alan, Amie, Andrew, axiomadmin, Brent, Debbie, Ian, Jc 
Forum Stats

15,208 Registered Members
15 Forums
23,963 Topics
423,622 Posts

Most users ever online:
883 @ 03/04/17 05:06 PM

Top Posters
Ken.C 18044
pmbuko 16437
SirQuack 13565
CV 11675
MarkSJohnson 11437
0 registered ()
212 Guests and
4 Spiders online.
Key: Admin, Global Mod, Mod
Newsletter Signup