Getting 14.4v

[DJDestiny]

This is tough for me ,
yes , i have Alpine MRV-400 Amp that is full of BJT's but i have no power consumption , i only know that the max amount of power before the fuses in it blow is 40A ( which is about 576W ) .

And i guess a tranny that should output nearly 14.4v after bridge rectification .
Can anyone point me in the right direction ? ( It in the amp has a SMPS already . )

[wintermute]

I assume you are wanting to run a car amp off the mains and need a correctly sized transformer to do this?

Since 14.4V is around the max with the alternator running, and nominally the battery power is 12V I would say that it is safe to have something a bit lower than 14.4V, you probably don't want to go over it too much though.

10V secondaries will give you around 14.4V (or perhaps 13.8V after diode losses) however this would be under full load. if the transformer has 10% regulation it will be closer to 15.1V unloaded (allowing for .6v diode drop).

9V secondary might be safer, but it could be marginal as to whether you would get the required 12V... and you also need to consider mains voltage variations. It would probably be wise to check the absolute limits of the amps input power (possibly 16V max), and size for worst case of 10% over on mains , this would give around 16.38V allowing for 10% transformer regulation... as you will need a big VA transformer regulation will probably be closer to 6% which should be ok.

With regards to the power required, that is a bit tricky, you could just go with say a 600VA 10V transformer and hope it is enough. 40A fuses would tend to indicate that it won't be drawing that much current in reality. However where are the fuse(s) is it a single 40A before the smps or are they rail fuses after the voltage has been bumped up?

Tony.

[luka]

two things, first, fuses won't blow at 40A, so peak and short power could be a lot more, but you would probably clip the output way before that. Second thing is, amp is an audio amp, and consumtion is much lower then one would thing, because of creast factor of the music. also depends on amp, how much energy has stored inside, most car amplifiers not much, but still some

what you want, if going with mains power amp, probably the most simple thing is to get PC supply, load 5V with some load, like few fans or something, and use 12v rail for the amp

[DJDestiny]

thank you for your input.
This amp is a mrv-400 a old one, but runs better at 14.4v
40A 2 20amp fuses .
Not sure where it is linked to as the fuses are on its exterior .
and also, i heard it runs hot, and at 14.4v it runs at 160W x 2 in bridge mode with 4 ohm. ( not 8 ohm but 4 )
I just need to feed it rectified and see how, i checked and its a SMPS inside .

[luka]

Do you really need that much power at home?? coz one way would be to use battery and charger

[AndrewT]

open up the amp and remove the SMPS.
Feed a new PSU direct to the amplifier power rails.

[DJDestiny]

Dude, the SMPS is beyond just 12v .

Making a amp head with this, you wouldn't want a battery while touring trust me.
And on top of that, a 12v PSU rated 500W isn't exactly cheap and i need 14.4v for 160 x 2 .

[luka]

from where do you get, that you need 500W?if you could get 200w consumption I would be o.O

[DJDestiny]

Look, its Class AB and can amplify to 320W .
400VA maybe, but there are two rail 20A fuses.
Searched around without much luck, this is a old but good alpine amp, back when Alpine made proper amps, this was top of the line , no doubt.
Its full of BJT's by the way.

[luka]

doesn't matter if it is 20kw amp, if your going to draw only 100w with music