watt conversion

[rizwan33]

i have a 1600w voltage convertor.it has a variable resistor of 250k in it that controls the output ranging 6-155 V AC. the convertor was made for 110V AC .i wanted to set variable resistance for an output of 12V AC.now can anybody tell me wether it will work to provide 12v AC and a current of approximatly 35-40A.form that output voltage , i want to operate a car audio amplifier to derive a 200 W sub-woofer.is the whole plan possible?

u could view the picture of watt convertor at:\

Google Image Result for https://ecx.images-amazon.com/images/I/316UKl2RKjL._SL500_AA300_.jpg

 

[crutschow]

What is the source of power for the voltage converter? What type of converter is this?

Are you going to convert the 12VAC to 12VDC to power the sub?

 

[rizwan33]

no i am to convert from 220vac to 12 vac.
u can view the picture of source at:

Google Image Result for https://ecx.images-amazon.com/images/I/316UKl2RKjL._SL500_AA300_.jpg

 

[rizwan33]

Carl
i am trying to convert 120 VAC to 12VAC
i dont know the type of supply so i am uploading pictures of supply
the transistor used is a BTA16

 

[Thunderchild]

well you convert 120 VAC to 12VAC with a simple transformer, most of your original post makes no sense at all

 

[tcmtech]

Looks like a standard phase controlled lamp dimer type to me.
The 1600 watt ratting is its maximum power at the line voltage so at 110 volts thats around 14.5 amps. That would likely be its working current limit at all voltages but I would never trust one of those to directly drive a amplifier at 12 volts output.

For an 12 volt audio amplifier power supply a good old battery charger of the right size with some good filter capacitors works rather well though. I have done it many times.

 

[rizwan33]

thanks tcmtech and thunderchild for yr suggesions.
actually i had these things in my drawer so i was just trying to figure it out wether my thinking was correct or not.
i know that a transformer will be a best possible solution.
this fourm is really useful so thanks again.

 

[Thunderchild]

always be careful of msrketing claims, sales people don't think like engineers, if you tell an engineer 1.6 KW he takes it as 1.6KW continuous under any condition, would interesting to see the small print to that claim

 

[rizwan33]

can u please tell what can be the specifications of a 220 to 12vac transformer to run a 350w woofer through an amplifier?

 

[Thunderchild]

what is the efficiency of the amp ? you will probably want around a 500 W transformer which at 12 V is producing 41.6 amps ! ouch put some VERY thick wire on that one.

is it a 350W RMS, music power or "marketing power" ?
if it is not RMS then you may well be able to use a smaller transformer,
250W for music power and
25W for "marketing power"

 

[rizwan33]

no 350w is not a RMS power.
approximatly how much will it cost such a transformer?
a rough idea.

 

[Thunderchild]

try Farnell / Electronic Component Distributors / Suppliers / Electronics, Electrical Parts, Electrical Components and Wholesale Electronics.

is it music power ? this is usually 2X the true RMS rating which is THE only relaible and credible means of measuring power capabilities of any device. RMS power is the actual electrical power used, so if your looking at 350W music power it is 175 W RMS, next you need to know roughly how efficient your amp is, this can be easily found by the amp type, a class AB amp is 30-50% efficient, if it is a high power amp it may well be class D, these are more like 70-90% efficient, if this is the case a 225W transformer should cope. The other thing to consider is will you really be running it at 175 W RMS (350" music power)? if not a much smaller transformer will cope but you need to know your limits or you will burn it out.

I run 70W speaker of a small 5+5W amp and really I could make the whole neighbourhood hear me if I wanted

at the end of the day you may get away with an old PC PSU but look carefully at it's 12V rail output amps

 

[tcmtech]

It would cost about what ever a 30 amp battery charger is worth in your location.

 

[Thunderchild]

It would cost about what ever a 30 amp battery charger is worth in your location.

you hit the nail on the head - find a currently available product and hack it !

 

[rizwan33]

i have viewed the specifications of my amplifier.
it is a d class amplifier
it is 1200w
with 4 x 300 watts (at 4Ω)
and a maximum current consumption of 60A

 

[rizwan33]

hey guys i have viewed the description of
Kenwood KAC-6404, 500W four channel power amplfier
it states that it would consume maximum of 19A at 12V dc
what does it means , because 19*12 are not equal to 500

 

[Thunderchild]

it means they are loosly stating musixc power of some sort and not RMS, this is why RMS is "the" only real comparison as it is clearly defined. 19*12=228, well considering amp efficiency thats 228*80%=182 W, at the end of the day for your home etc 10W is plenty

 

[tcmtech]

60 amps at 12 volts would be 720 watts. Most music does not push a amplifier at its full capacity for extended periods so still a hacked battery charger with a few big capacitors, a pair of 100K uf or larger audio super caps, would probably still have plenty of reserve capacity to work with. A good 30 amp battery charger with a 200 amp boost can take considerable overloads for short periods and would likely have little trouble with a 500 or 750 peak rated amplifier.

I used to be into the big car audio stuff years ago. My car ran around 1000 watts RMS at the speakers and pulled around 1300+ watts at the 12 volt source. I used an old commercial 75 amp charge/300 amp boost battery charger as the plug in power source and it rarely ever overheated to the point of shutting itself down.

The down side to the cheap battery chargers is they usually don't have built in overheat protection and can burn themselves up if overloaded too long.