Hello guys.
...at first I want to apologize for my bad english. I have no practice at all, and only remember a little of school education in this language. Please don´t think too bad of me, therefore! ^^ ...at second I have to say, i´m practiced in working with (simple constructed) high voltage projects, and know about the hazards, and what to do for security. But --- in audio the only project i did, was a LM 3886 amplifier (as Siegfried Linkwitz showed on his site).
Now I have a problem: I have nearly zero money, but want to build an amp with an output of about 800 - 1200 (best would eventually be 1000) W RMS. From a former project i have some probably usable parts in stock. This is the simplest usable scheme i could find. What do you think about it? Is it good for a subamp? I got (each 24 pcs) IRFPC50A(from IRF) and IRF450(but from Harris, less I.ds and also P.tot). The IRFPC50A seems to have nearly the same parameters like IRFP448, but, unfortunately, only nearly...
Could I use one of this FETs? And when, what do you think, how many pairs should i use for 1000 W RMS at 4 Ohms? And can I still use the showed gate driving BJTs (Q10 and Q11)? Or stronger ones, and when, then which? (Only thing I really know, is, that I´d have to use bigger fuses...) I got two transformers, rated at 2,5 kVA (permanent), 13,3 kVA (short time), with center tap, and by changing primary taps, i can get (+/-) 70.96, or 74.35, 78.05, 81.32 (8 steps of ~ 3.5 V) 102.72 VDC (without diode losses). These are a little too big, but I have no other. (Yes, I know, I only need one... ^^)
Is this schematic acceptable? (No real foults, I mean.) The sound must not be "audiophile", it only should work, without bigger complications. I know, normally in this modern time, if one wants to get so much power, he should do with class D, but this (now) is too complex for me as a more electric (and not electronic) experienced guy. And cannot make PCB, so I´d be glad if I must build the driver stage only once, cause I must use "breadboard" (I think this is the name of this in english), and combine with point-to-point (better silvered copperwire or is varnished enough?), where necessary.
I have one further schematic (which HAS already the possibility to ad enough FETs [the gate-driving BJTs, who drive 2 x 5 IRFP 460, surely would drive a bigger number of smaller FETs, e.g. 2 x 10 of my IRFP 450 [Harris, not to forget, otherwise, if they were "real" IRFP450s from IRF, 2 x 8 would be roughly enough, i think] , cause it is mentioned in the text, that the driving capability is not exhausted) but this needs one voltage 10 volts higher than rail, and i don´t have a transformer with those further tap. (Like I wrote, my voltage changes by changing PRIMARY...) I don´t know, if it would be a good idea, to ad some windings, but... I think, it would not.
(Isolation etc.) But, the good thing with the second circuit is, it has a complete description of getting the amp started. And has a second pot, to do this... (Begins with: "Put some 100 Ohm resistors in place of the fuses..." --- really good described, a fine thing.)
I don´t even know what kinds of resistors (evtl. metal film ok?), capacitors (film types like MKS ok? --- except the unipolar electrolytic, of course), and what kind of inductor should be good? (From the inductor in scheme 1 there´s no information at all, and cause I´m not experienced at all, I have no idea. Should it be ferrite or plated iron? Have or have not an air gap, and when, how wide? Only thing I am sure, copper wire should be thick enough.)
Please, help me! Could I make it work?
(P.S.: In a thread I found, one guy said, it would be cheaper, to buy a used PA amp, than build an amp of this power. I hope, he meant the costs of the transformer (my ones I got in former times, when I had money, for 200 Euro each) and the Power-FETs, cause used PA-amps of this power never come under 100 or more Euros --- I simply don´t have, and wouldn´t get, such an amount of money, for now)
First possibility, which fits my transformer:
400 W MOSFET Audio Amplifier Using IRFP448 : Tasel
Second possibility, which needs 10 "extra" Volts:
600 Watt Quasi Amplifier With Mosfet IRFP460
...or do you have a better one?
Greets,
FQR
...at first I want to apologize for my bad english. I have no practice at all, and only remember a little of school education in this language. Please don´t think too bad of me, therefore! ^^ ...at second I have to say, i´m practiced in working with (simple constructed) high voltage projects, and know about the hazards, and what to do for security. But --- in audio the only project i did, was a LM 3886 amplifier (as Siegfried Linkwitz showed on his site).
Now I have a problem: I have nearly zero money, but want to build an amp with an output of about 800 - 1200 (best would eventually be 1000) W RMS. From a former project i have some probably usable parts in stock. This is the simplest usable scheme i could find. What do you think about it? Is it good for a subamp? I got (each 24 pcs) IRFPC50A(from IRF) and IRF450(but from Harris, less I.ds and also P.tot). The IRFPC50A seems to have nearly the same parameters like IRFP448, but, unfortunately, only nearly...
Could I use one of this FETs? And when, what do you think, how many pairs should i use for 1000 W RMS at 4 Ohms? And can I still use the showed gate driving BJTs (Q10 and Q11)? Or stronger ones, and when, then which? (Only thing I really know, is, that I´d have to use bigger fuses...) I got two transformers, rated at 2,5 kVA (permanent), 13,3 kVA (short time), with center tap, and by changing primary taps, i can get (+/-) 70.96, or 74.35, 78.05, 81.32 (8 steps of ~ 3.5 V) 102.72 VDC (without diode losses). These are a little too big, but I have no other. (Yes, I know, I only need one... ^^)
Is this schematic acceptable? (No real foults, I mean.) The sound must not be "audiophile", it only should work, without bigger complications. I know, normally in this modern time, if one wants to get so much power, he should do with class D, but this (now) is too complex for me as a more electric (and not electronic) experienced guy. And cannot make PCB, so I´d be glad if I must build the driver stage only once, cause I must use "breadboard" (I think this is the name of this in english), and combine with point-to-point (better silvered copperwire or is varnished enough?), where necessary.
I have one further schematic (which HAS already the possibility to ad enough FETs [the gate-driving BJTs, who drive 2 x 5 IRFP 460, surely would drive a bigger number of smaller FETs, e.g. 2 x 10 of my IRFP 450 [Harris, not to forget, otherwise, if they were "real" IRFP450s from IRF, 2 x 8 would be roughly enough, i think] , cause it is mentioned in the text, that the driving capability is not exhausted) but this needs one voltage 10 volts higher than rail, and i don´t have a transformer with those further tap. (Like I wrote, my voltage changes by changing PRIMARY...) I don´t know, if it would be a good idea, to ad some windings, but... I think, it would not.
I don´t even know what kinds of resistors (evtl. metal film ok?), capacitors (film types like MKS ok? --- except the unipolar electrolytic, of course), and what kind of inductor should be good? (From the inductor in scheme 1 there´s no information at all, and cause I´m not experienced at all, I have no idea. Should it be ferrite or plated iron? Have or have not an air gap, and when, how wide? Only thing I am sure, copper wire should be thick enough.)
Please, help me! Could I make it work?
(P.S.: In a thread I found, one guy said, it would be cheaper, to buy a used PA amp, than build an amp of this power. I hope, he meant the costs of the transformer (my ones I got in former times, when I had money, for 200 Euro each) and the Power-FETs, cause used PA-amps of this power never come under 100 or more Euros --- I simply don´t have, and wouldn´t get, such an amount of money, for now)
First possibility, which fits my transformer:
400 W MOSFET Audio Amplifier Using IRFP448 : Tasel
Second possibility, which needs 10 "extra" Volts:
600 Watt Quasi Amplifier With Mosfet IRFP460
...or do you have a better one?

Greets,
FQR