Modify car amplifier power supply.

[Dicko101]

Hi, I have a lot of surplus car audio and although I always opt for home audio I have used car audio for home applications before with decent results, I still drive my 12" transmission line sub with a car amp and PSU with no issue at all. My question is though, most people that use car amps outside of the car just try to find a DC power supply with enough amps to drive the system, I'm wondering how hard it would be, especially in amplifiers with separate supply and amp sections, to do away with the 12v supply all together and build a supply to drive the amp section directly without going to 12v DC first, would that be feasible? One amp in particular I have that I'm considering doing this with is an Alpine MRV-1507. Any thoughts?

 

[davenn]

My question is though, most people that use car amps outside of the car just try to find a DC power supply with enough amps to drive the system, I'm wondering how hard it would be, especially in amplifiers with separate supply and amp sections, to do away with the 12v supply all together and build a supply to drive the amp section directly without going to 12v DC first, would that be feasible? One amp in particular I have that I'm considering doing this with is an Alpine MRV-1507. Any thoughts?

not really sure what you are getting at ... the PSU in the stereo running the amplifier and all else is designed to run the power amp section
you would be making life difficult for yourself trying to build another 12V PSU for the power amp ... why do it when you already have one ?

schematic of the gear would be essential before any mods could begin

 

[Audioguru]

The Alpine MRV-1507 car amplifier obviously has a stereo amplifier that produces 150W to 225W per channel into 4 ohms with a supply to its DC-DC converter of 12VDC to 14.4VDC. It is probably class-AB (not class-D) so with 300W of total output its heating is about 200W so its power supply must produce about 500W.

300W into 4 ohms is 98V p-p so the power supply voltage is probably about 108VDC or +/-54VDC. The max current is 500W/108V= 4.6A. It has a cooling fan that might operate from the original 12V in a car and its current is unknown. The remote turn on also uses 12VDC.

 

[davenn]

300W into 4 ohms is 98V p-p so the power supply voltage is probably about 108VDC or +/-54VDC. The max current is 500W/108V= 4.6A. It has a cooling fan that might operate from the original 12V in a car and its current is unknown. The remote turn on also uses 12VDC.

the output transistors (IRF540 FETs) are running at 49V on the drains

 

[Dicko101]

not really sure what you are getting at ... the PSU in the stereo running the amplifier and all else is designed to run the power amp section
you would be making life difficult for yourself trying to build another 12V PSU for the power amp ... why do it when you already have one ?

schematic of the gear would be essential before any mods could begin

I just thought if it is going to be used long term in a home theatre situation, which it is now as I was having trouble getting a good power amp for my front channels and it pairs with my speakers really well, they had a fairly weak midrange on the Sony DA5300 receiver but this amp makes them sound much fuller and more dynamic (surprisingly), then it would be better to provide the required voltage with plenty of current directly to the amplifier with a purpose built supply. It seems inefficient to add a device to supply 12-14v just because that is what the normal application would restrict it to, that restriction has been removed. I just figured it would bottleneck the available power with an off the shelf 12v supply. Plus although it's obvious a lot of stuffing around when a 12v supply will probably do, its something I've wanted to try for a while, I might even make a more suitable enclosure if I'm already going to that trouble, someone snapped off one of the output tabs so if I put it in an enclosure I can put decent binding posts etc on it.

 

[davenn]

I just thought if it is going to be used long term in a home theatre situation, which it is now as I was having trouble getting a good power amp for my front channels and it pairs with my speakers really well, they had a fairly weak midrange on the Sony DA5300 receiver but this amp makes them sound much fuller and more dynamic (surprisingly), then it would be better to provide the required voltage with plenty of current directly to the amplifier with a purpose built supply.

you will need a 12V supply capable of ~ 12 Amps
that's around 6 amps per channel and allows for a bit of headroom


Dave