ok , it clips at around 45v rms at 4 ohm load and 40v rms at 2 ohm load ,,,,,,,,
what if i want 60vrms at 4ohhm ,,,,, do i only need to increase supply voltage
The transformer is to small for 2 ohm load.
1200w/(60+60v) = 10A You should not load it more than absolute max 7A DC.
7A DC into an output stage that is conducting halv time will be 14A average or 20A top to the speaker.
20A *4ohm = 80v. That means at 4 ohms you load the transformer max if you play at the amplifiers limit.
For 2 ohms it would be vise to have 1 transformer more. And with respect to the mains fuses it can be good to first switch on one transformer and then the other. And maybe 2x40 000uF.
I recommend to have separate rectifiers so it is no risk for out of phase connection.
1200w/(60+60v) = 10A You should not load it more than absolute max 7A DC.
7A DC into an output stage that is conducting halv time will be 14A average or 20A top to the speaker.
20A *4ohm = 80v. That means at 4 ohms you load the transformer max if you play at the amplifiers limit.
For 2 ohms it would be vise to have 1 transformer more. And with respect to the mains fuses it can be good to first switch on one transformer and then the other. And maybe 2x40 000uF.
I recommend to have separate rectifiers so it is no risk for out of phase connection.
45V across 4 ohm is over 10A of current. It doesn’t take much resistance to bleed off a few volts. 1 ohm of parasitic resistance somewhere, and you’ve bled off 10V already. Your PSU has internal resistance, so do the wires, the output transistors aren’t exactly 0ohm across even at full saturation and you lose a little bit in the degeneration resistors. Designing for those kinds of currents can be challenging!
Food for thought:
You have gotten lots of good help. Please keep working on your project.
The SOA @ 160 volts, 25 degrees, 100ms single pulse is only 100ma per device (800ma to load).
This maybe OK for a real restive load, however the reactive speaker typically are 45-60 degrees. Reactive loads store energy and the SOA will be exceeded, maybe smoke & flames will follow.
I’m not trying to scare you, but there are several things that are unknow or not yet reveled. Fan, flyback diodes, input clamping, square wave overshoot, bode plot, thermal tracking, current limiting, ripple current ratings, etc.
You have gotten lots of good help. Please keep working on your project.
The SOA @ 160 volts, 25 degrees, 100ms single pulse is only 100ma per device (800ma to load).
This maybe OK for a real restive load, however the reactive speaker typically are 45-60 degrees. Reactive loads store energy and the SOA will be exceeded, maybe smoke & flames will follow.
I’m not trying to scare you, but there are several things that are unknow or not yet reveled. Fan, flyback diodes, input clamping, square wave overshoot, bode plot, thermal tracking, current limiting, ripple current ratings, etc.
SOA at 160 volts isn’t all that relevant - but at 80 volts it IS. Plan for half the peak current at Vcc. C5200’s guaranteed SOA isn’t as high as the old C3281 was. OnSemi’s version (M/NJL3281) is better in that regard.
In a Push Pull output circuit when the top device Qt is turned full ON, its Emitter is setting @ Vcc-2 (+78v) and the lower Ql Emitter is setting @ Vcc-3v (+77v), it’s Collector is @ Vdd (-80v). Who is turning on sucking out the current of the reactive load? It’s Ql @ 157v pulling down the load.
Fully reactive load is 90 degrees out of phase, not 180. Peak current would occur at zero crossing, or about 80V on the transistor.
A fully reactive load makes no sound. Real speakers get to about 60 degrees, but the impedance minimum does not occur there. It’s practical to consider 30 degrees AT the minimum. The minimum physically occurs at ZERO degrees, but it’s still only a few percent above the minimum at 30 degrees for a real woofer driver that hits 60 degrees. Many do, but more phase is exceptionally rare. Such a driver has very high (double digit) Qms meaning very low mechanical losses. Then go and put any damping material in the box, and it spreads out that impedance peak and reduces maximum phase shift. So considering really crazy phase shift doesn’t make any sense for the real world. 30 degrees at Zmin, and for practical purposes the amp is safe.
A fully reactive load makes no sound. Real speakers get to about 60 degrees, but the impedance minimum does not occur there. It’s practical to consider 30 degrees AT the minimum. The minimum physically occurs at ZERO degrees, but it’s still only a few percent above the minimum at 30 degrees for a real woofer driver that hits 60 degrees. Many do, but more phase is exceptionally rare. Such a driver has very high (double digit) Qms meaning very low mechanical losses. Then go and put any damping material in the box, and it spreads out that impedance peak and reduces maximum phase shift. So considering really crazy phase shift doesn’t make any sense for the real world. 30 degrees at Zmin, and for practical purposes the amp is safe.