DIY PSU for car amp (but for home use)

[BNK]

I can get an high end 2x400W car amp (at 14.4V).
Where can I find design/kits for such a PSU using a toroidal transformer?

 

[dark_avenger]

cheapest easyest way is to get hold of old computer power supplys and hook 2/3 of them together with diods on each....

or

toriodal -> rectifer -> amp

 

[BNK]

Is it that simple? No problems ahead?
btw. I can get an high end amp 2x400W into 8 ohms, 0.09% thd, s/n 100db for ~300$.

Does it worth it? or you can build a better one for less?

 

[dark_avenger]

power supplys for car amps don't need to be to complex because they have circuitry built in to regulate power as power from an altinator fluctuates alot.

 

[BNK]

It's an interesting point as high end car amps are much cheaper than home high end amps.

This amp is rated at 2x400W rms at 8 ohm.
How many PC PSUs and rated at (watts)?
I can get a 500W PSU for 10$.

 

[dark_avenger]

if u ask around u shoulden't have much trouble finding some second hands ones either cheap or free. computer psu's are rated for all there voltages you will have to look at the sticker on the power supply and cheack the current rating for the +12 rail.

 

[BNK]

I think I have one or two (~300W).
How many do I need?

I have a rectifier of a gainclone I didn't finish.
As I understand from you, there is no gain of having a toroidal transformer (more expensive)?

 

[djk]

The 12V outputs on 500W supplies are not good for a lot of watts. The bulk of the power is on the 5V lines. The regulation feedback is usually derived from the 5V lines too.

Just bypass the switching supply on the car amp and feed it what it needs from a 50hz/60hz transformer, bridge rectifier, and caps.

 

[x84andrea]

it's not a good idea, the car amp have a protection on the psu, and use pwm for produce hi-voltage controlled by a microprocessor, if there aren't 12v the amp don't start or doesn't work well , can you use a big trasformer (800-1kw) at 12v and can you use a big capacitor, in the cars are used not the uF but the farad... 1-2farad is good, but also uses asmaller capacitors, it's too fast!!!!

don't use a 1n4007... use 2-4 large diode (100A is good), ore 2 bridge diode (50a) but isn't recommendet.

the power is rms or max?

 

[BNK]

it's not a good idea, the car amp have a protection on the psu, and use pwm for produce hi-voltage controlled by a microprocessor, if there aren't 12v the amp don't start or doesn't work well , can you use a big trasformer (800-1kw) at 12v and can you use a big capacitor, in the cars are used not the uF but the farad... 1-2farad is good, but also uses asmaller capacitors, it's too fast!!!!

don't use a 1n4007... use 2-4 large diode (100A is good), ore 2 bridge diode (50a) but isn't recommendet.

the power is rms or max?

The power is rms.
This is the amp:
http://www.linearpower.com/lpspecs.html
Model:2202 moded to 2x400W at 8ohm.
The site contains description of the amp.

Can you recommend a PSU kit that I can use with that?
Do I need a toroidal transformer or a "regular" one is good enough?
Do I need to add a car cap at the front?

 

[tangmonster]

99% of car amplifiers are overrated a LOT!!

fitting an 12V powersupply that can supply huge amounts of current is not going to be as simple as a few computer powersupplies.

and in the end you will have a system that

takes AC down to 12 DC and then tha amplifier circuitry will make it a high voltage again.

rather strip a cheaper amplifier and try and disconnect the voltage inverter stage and build a decent high voltage power supply.

 

[jerluwoo]

I've converted a couple of car amps for home use. First open the top so you have access to the torroidal transformer inside. Feed the amp 12 volts (13.8V to get its rated output) and measure the ac voltage across the the secondary of the torroid. Once you have this measurement you can find a transformer that has close to the same secondary voltage. A little less voltage is fine but do not use any higher than what you measured. Next we go about 1/4 inch out from where the secondary of the torroid inside connects to the pc board and cut the trace. Take four male spade plugs and get a dril bit the same size as the crimp end of them (remove the plastic cover first) and drill a hole on both sides of the traces you just cut. Solder the spade plugs in, you may need to trim a little off the end of the plugs so they fit without grounding on the bottom cover of the amp. Now you can add female spade plugs to the transformer and plug it in and also make a jumper wires with two female ends so the amp can still be used in a car if need be.

 

[BC]

SPECS

Hi BNK,

I went to your posted WEB site for Linear Power and I am confused 😕

The specs for model 2202 are as follows:

110Wx2 @ 4 Ohms stereo using 12.5 volts DC

Mono rating @ 4 ohms is 250 watts (bridged)

I did not see any ratings at 8 ohms. 😕

I would say that auto amps are usually (never?) rated for 8 ohms.

You may wish to check with Linear Power Inc.

😎


BC

 

[BNK]

Re: SPECS

I've converted a couple of car amps for home use. First open the top so you have access to the torroidal transformer inside. Feed the amp 12 volts (13.8V to get its rated output) and measure the ac voltage across the the secondary of the torroid. Once you have this measurement you can find a transformer that has close to the same secondary voltage. A little less voltage is fine but do not use any higher than what you measured. Next we go about 1/4 inch out from where the secondary of the torroid inside connects to the pc board and cut the trace. Take four male spade plugs and get a dril bit the same size as the crimp end of them (remove the plastic cover first) and drill a hole on both sides of the traces you just cut. Solder the spade plugs in, you may need to trim a little off the end of the plugs so they fit without grounding on the bottom cover of the amp. Now you can add female spade plugs to the transformer and plug it in and also make a jumper wires with two female ends so the amp can still be used in a car if need be.

Wow, I thought maybe it can be more simple.
Why do I need to bypass the inside toroidal and not just feed it?

Hi BNK,

I went to your posted WEB site for Linear Power and I am confused 😕

The specs for model 2202 are as follows:

110Wx2 @ 4 Ohms stereo using 12.5 volts DC

Mono rating @ 4 ohms is 250 watts (bridged)

I did not see any ratings at 8 ohms. 😕

I would say that auto amps are usually (never?) rated for 8 ohms.

You may wish to check with Linear Power Inc.

😎


BC

There is a modification part on the site where u can send your amp for modification.
I just bought it used (didn't even get it), and I will check that out.

You are right, car amps are usually rated for 4 ohm (2 ohm and 8 ohm bridged are mentioned in some).

 

[dark_avenger]

computer psu will work there is no need to bypass the internal transfomer however it would be better. i've had a car amp running the subs for my home threatre system for months now and haven't had a problem with it or the comp psu

 

[Eva]

This amplifier is going to produce only 2 x 60W into 8 ohms at best. There are plenty of better alternatives for 8 ohm home usage.

 

[BNK]

This amplifier is going to produce only 2 x 60W into 8 ohms at best. There are plenty of better alternatives for 8 ohm home usage.

It was modded to 2x400W peak power (not rms as I thought).

 

[djk]

" or you can build a better one for less?"

Yes, I could.

With a little scrounging, you could too.

djk []
diyAudio Member

Online
Registered: Feb 2001
Location: USA


Post #4
Ignoring the problems with the front end, you're going to need about ±80V from a typical supply to get the power you're expecting to see.

I would suggest a 55-0-55 400VA transformer and a pair of 10,000µF caps.

You want a simple front end with a $6 pcb?

http://www.audioxpress.com/bksprods/pcbs/nelsonpass.htm

http://www.passdiy.com/pdf/a40.pdf

~snip~

Post #4
http://www.passlabs.com/images/projects/a40f6.jpg The circuit board for this amp is the deal of the century. Still available for only $6 from Old Colony! Who cares? It's only 40 watts. Not really. Jumper Q11 and change R9 to 27K 1/2W(Pass suggests this for the A40 if you are having trouble finding the fet, only use 10K for his design) http://www.passlabs.com/projects/a40_subs.htm Change Q1,2,3,6 to the MPS8099 or 2N5551. Change Q4 and Q5 to the 2N3440/2N5416 pair. Use a heatsink on these. Change R10 to 68 ohms. Delete R13 and D3. R11 will be selected for bias. C4 will be for high frequency response. R14,15 will be changed to one 220 ohm per ouput device. The outputs are to be two each BUZ900D/905D http://www.semelab.co.uk/magnatec_mosdata.htm This will give 400 watts RMS with a 53V+53V 800VA transformer and only two pair of outputs! Don't forget to add 10V gate zeners and output flyback diodes.

~snip~

Use an EF output stage with 4 pair of MJ21139/94 type outputs, MJE15032/33 type drivers.

Basic plan (4X Q7, Q8):

http://www.diyaudio.com/forums/atta...tamp=1040960593


IP: 208.252.113.xxx
06-24-2006 02:29 AM Quote:



burnedfingers []
diyAudio Member

Offline
Registered: Nov 2002
Location: USA


Post #5
Once again you have it.

Mr.DJK designs an amplifier.

I have built this A40 as designed by DJK using MJ15024's and MJ15025's. I beat the living hell out of it without ANY problems.
Well worth the effort in my opinion.

djk []
diyAudio Member

Online
Registered: Feb 2001
Location: USA


Post #6

The amp burnedfingers built has 6X MJ15024/25 and runs on about ±93V for about 600W/4R for his subwoofer.

 

[x84andrea]

400wrms.... to 400wpeak...
for this power is good a computer psu, it's have a 150w-300w at 12v continue, but to start it you need to short-circuit a pin with a 5v, it's easy!
but this psu isn't good for audio, it's not very fast to give out high current, it's raccomanded a transformers 200-300w it's good, and a 35a bridge!
ok?
can you measure the volt on the cap? thanks andrea