MJ15003/15004 1200Watt @04ohms audio power amplifier schematics

blackpower

New member
This is an amplifier using MJ15003/15004 and capable of delivering about 1200watt rms with an output load of 4 ohms. Don't hesitate to question me for any trouble!!! enjoy yourself with it!!! For a better resolution, print out the schematics on two A4 papers and combine them after.
 

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vedmitra

Member
Hay Blackpower do you have any quasi version for this amp.and please provide p.c.b & layouts for this if you have.regards
 

blackpower

New member
yes I have a 400w version for this amp but using BD251C/250C output transistors. I am currently drawing the pcb for this amp but I have already tested the amp and it's ok.
I will share the pcb here when it's ready
 

vedmitra

Member
Thanks for the reply blackpower.I think i could not clear out my self I was talking about only using 'n' transistors as 2n3773. not npn and pnp. hope you have some high wattage version for same .regards.
 

AndrewT

New member
700W is a more sensible target for a 7pr output stage using mj15003/4 (250W BJT).
1200W into 4ohms requires an output of 98Vpk. That in turn would require supply rails of around +-110Vdc. But the mj15003/4 is limited to 140Vce They cannot be operated on +-110Vdc supplies.

If Ved wishes to use 2n3773 (150W BJT) then the supply rails must be reduced to <=+-70Vdc. A sensible maximum output for a 7pr output stage would be 14*150/5 ~420W.
With +-70max rails that will normally run at ~+-65Vdc expect the maximum output to be around 58Vpk.
58Vpk into 4r0 is ~420W. Just matches the power limitation of the 3773. Use a 45-0-45Vac 625VA transformer.
 

vedmitra

Member
Thanks Mr. Andrew T,
Just your calculation, 98vpk for 1200 watts, V x V/r=w ; 98 x 98/4 = 9604/4= 2401, I am sorry but is that correct?
Q. Why it is only voltage which is considered for output wattage, Don't we have any role of current for output, Is the Ohm's Law W= V x I is wrong.
1200/98 = 12.2 amps. okay, 1200/50 = 24 amps. It is true that output impedance will go low for high current Amp.
What people around me needs is an Amp which can work on extreme low impedance load,say down to 0.5 ohm's, and Amps I have made are serving that purpose.
Off course I always use High current Transformers, assuming losses for a 1000 watts Amp I always use around 2000 watts Transformer. so the supply voltage won't drop too much during full load. my 70+ - volt rails gives 66 volts+ - even during full load,
And I am happily using this short of amps without problem in Live programes since long.
 

AndrewT

New member
P=IV=V^2/R=I^2R
If you know the voltage then use the P=V^2/R
but you must use the rms (root mean squared) value for that formula.
If you want to use the peak value for a sinewave signal then the formula becomes
P=V^2/R/2

P=98^2/4/2 = 1200.5W

I can't be bothered with the rest.
 

vedmitra

Member
OHM's Law.

This is the chart wheel of OHM's Law
 

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