Power supply for car amp

[frankwas]

Hi all!

It's been a while since I last posted here. Thanks for everyone that helped on my previous designs!!!! Now, I have yet another idea that I want to build. I have been searching around the net for a car amplifier psu but  to no avail. I found a psu that uses TIP transistors with a 24V 35A transformer. Correct me if I'm wrong but isn't that a 24x35 = 840VA transformer? They are rare where I live. The closest I can get is a 50V 1000VA and it is very expensive!

Let me get to the point! I have a 1400W (about 250Wrms) car amp lying around that I would like to power from my house power, 230V. I thought that if I take a transformer that is say 300VA, 12V, use a bridge rectifier with a 400VA rating and a nive juicy capacitor, wouldnt that be sufficient? Please help me if I'm completely off track.  :P

Thanks in advance!!

[ante]

Hi frank,

If I where to power a car amp for indoor use I would find out how its internal power is arranged first. I don’t know about the one you’ve got but I seen a few and most of them has a 12 VDC to +- 35 – 70 VDC converter inside. What I would do here is tap in between the converter and the amp with my own PSU. This will allow me to use a cheaper transformer and avoid the high currents.

[frankwas]

Ok. I have looked inside, and all I can see is a toroid-like inductor and a few caps. Should I measure the voltage rating and go from there? What type of psu would I then need?

[SM2GXN]

Hi frankwas!

This link will give you an idea about how it looks like in your car amplifier, guess you need at least 1000VA transformer for your amplifier if you want to rock real hard, 1400W that is lots of power, your amplifier might have more than two channels, can you take a snap shot of the inside?.
Open the ampifier and run it from a 12 volt battery if you don't have a power supply that can handle the current needed. Measure from the the center tap of the transformer to the + and - side of the rectifier, the voltage reading you get is what you need  ;)
The bridge rectifier usually consists of two 3-leg devices TO220 packages with two diodes in each, they are usually marked with diodes on their bodies and mounted to the heath sink.
Someone will probably say that a bigger transformer is needed and that is both true and false, all depends on how loud you want to play  ;D


http://sound.westhost.com/project89.htm

[frankwas]

Hey.

Ok, that sounds about exactly what the amp is made up of. I'll hook it up and then see what I get and post back. I also need to get a cam for the snapshot. As soon as I have done this, I will post back as soon as possible! The amp isn't 1400W rms, the RMS of the amp is about 300 - 400w at the most. I will be playing two 125W rms subs (each) at about 80 percent power.

[ante]

If the amp was rated 1400 real “whats” the input current would be almost 200A @ 12VDC!  :o
The conversion from 230VAC to 12VDC and up again to something like 2 X 60VDC would be ineffective and a wasteful. A 500VA transformer will do the job with plenty of headroom. You will have to (as SM2GXN suggested) find out the voltage inside though. And also a picture and if possible a schematic would be nice! ;D

[Sukhbinder]

You may try out an PC power supply. u can get one quite cheap these days and they provide about 25-30A at 12V depending on the wattage of the supply ( u can have a 400W supply for a home PC or a higher one used in servers) u may need to connect some load to the 5V output of the supply also as some supplies do not work well without it ( try installing some cheap cooling fans or some LED lights to the 5V supply, maybe it will work out well) ;)