Subwoofer - Home Power supply transformer?

[02ryan48]

i have a subwoofer intended for a car and i'm looking to hook it up in my bedroom. i currently have it set up to use a transformer which steps it down to 12v 3a and it runs however only on minimum gain, how many amps can i safely pump into it and what kind of transformer do i need? i would really appreciate if you could link me one, i'm really new to all this kind of stuff and honestly don't know what i'm looking for, thanks in advance.

Below are pictures of how it is currently set up:

 

[Someone Somewhere]

I can't read it properly, but the fuse appears to be 25A in the pic.

Does the sub have a rated current or power?

I'd strongly suggest a lot more than 3A, though. That's only ~40W, and is probably limiting quite often.

You can't put too much current into them - they just supply whatever it's drawing. However, really high current supplies (40A+) can be dangerous if there's a fault, because they basically arc-weld.

 

[dish_moose]

You need to look at the specs for the sub amplifier a see how much current it needs. I'm betting more than 20 amps.
-Bruce

 

[02ryan48]

I can't read it properly, but the fuse appears to be 25A in the pic.

Does the sub have a rated current or power?

I'd strongly suggest a lot more than 3A, though. That's only ~40W, and is probably limiting quite often.

You can't put too much current into them - they just supply whatever it's drawing. However, really high current supplies (40A+) can be dangerous if there's a fault, because they basically arc-weld.

Yes, that's correct it's a 25a fuse, thank you for highlighting that, i guess that's a good place to start. In that case are these the kind of power supply i should be looking for?

http/www.amazon.co.uk/Graupner-100-240-Power-supply/dp/B002WE0CNW/ref=sr_1_47?ie=UTF8&qid=1394977839&sr=8-47&keywords=12v+25a+power+supply

http/www.amazon.co.uk/Switching-Power-Supply-Driver-Strip/dp/B00HVTRUJC/ref=sr_1_20?ie=UTF8&qid=1394977827&sr=8-20&keywords=12v+25a+power+supply

 

[Someone Somewhere]

The other thing you can do is pick up a computer PSU and jumper the power switch on, and ignore the 3.3/5V rails.

I'd avoid the second one, because a voltage selector switch tends to indicate a lack of APFC, which is a sign of poor quality construction.

 

[02ryan48]

The other thing you can do is pick up a computer PSU and jumper the power switch on, and ignore the 3.3/5V rails.

I'd avoid the second one, because a voltage selector switch tends to indicate a lack of APFC, which is a sign of poor quality construction.

To be honest, i'm very new to electronics and I wouldn't know how to go about doing this suggestion, is it possible you could give me a rough guide on what i should get to do this and how to do it or redirect me to something a little more simple?

 

[Someone Somewhere]

I can't find any links that look reasonable, so I'll write it out.

Permanently connect the GREEN wire on the big 24-pin connector to any of the BLACK wires. This forces the PSU to stay on, instead of only being on when the motherboard tells it to. Alternatively, you could put a switch in here to control it.

Pull the YELLOW (+12V) and BLACK (ground) wires out of either the CPU or GPU connectors. Because we're pulling a lot of power, we want a couple of each. Connect them to what you want to power.

Cut off or tidy away anything else.

 

[02ryan48]

Okay, i'm going to go and see if i have a 300w psu anywhere and i'l try it out, thankyou for all the help!

 

[dish_moose]

Someone said"The other thing you can do is pick up a computer PSU and jumper the power switch on, and ignore the 3.3/5V rails."
Problem: most computer power supplies will not put out the proper current on the 12v Rail if the 5/3.3V rails are not loaded. I have used many older psus but I had to put in a 2 ohm load for the 5v supply.
-Bruce

 

[02ryan48]

Following this, i've gotten a psu and jumped it, i then tested the connectiond using a voltmeter and the resuting volt was 11.97 however it stopped working and after restarting it it only gives out 1v, what has happened?

 

[dish_moose]

On most computer psus - the 12v rail will not work if the 5v rail is not loaded - something connected to it.
-Bruce

 

[sora]

As long as you have a good quality PSU it should personally work.

 

[dish_moose]

It has nothing to do with the quality - the design of most computer psus will not develop voltage at the 12v rail unless the 5V rail is loaded - been there - done that!!!
-Bruce
I am an electronic tech with 30 years experience and at the University where I work we use many of these psus in the lab. Every one that has been deployed was modified to put a dummy load on the 5v rail - a 2 ohm power resistor.

 

[Someone Somewhere]

Those with individual regulation might work, group usually won't. Depends on the type, not so much the quality. There are very good group-regulated PSUs out there.

 

[dish_moose]

Chances are a 300W computer supply will not have completely separate regulator sections. I have not run a cross a low cost psu that we have modified into a lab power supply that did not need a "dummy" load.
Bruce

 

[02ryan48]

Well, I've tried using the PSU and since i was only getting 1v out of it, it didn't work... I'm just going to put this to bed for a little while and i may come back and add a dummy load as you were mentioning, dish_moose, although i will probably just fork out the cash for some kind of power supply like this
http/www.amazon.co.uk/Pro-Peak-Power-Supply-13-8v-275W/dp/B000OZQ44W/ref=sr_1_11?ie=UTF8&qid=1395089142&sr=8-11&keywords=20+amp+power+supply
http/www.amazon.co.uk/P9R-SWITCH-MODE-13-8V-20AMP-SUPPLY/dp/B00FJWUCVQ/ref=pd_sim_sbs_k_h_b_cs_7?ie=UTF8&refRID=03CREHFRF2X1FX7C4JH0