You are going to have to double that to cover SOA....
Yes correct I ran the numbers , sounded low on face value ....
I use the 4times rule for mosFETs and the 5 to 6 times rule for BJTs.
The rule being.
Multiply the maximum rated output power by that "factor" to determine the total device power rating that should be used for reliable operation at more than ordinary domestic duty.
If you want 600W of maximum power into your rated speaker impedance then provide ~ 3000W to 3600W of device power rating.
8pr of 200W devices is 3200W. 8pair is in the ballpark.
Now you must prove to yourself that 8pair is correct for that 600W of maximum output power. You can either model it and determine from experience with your model that it is likely to work or you can destructively test it to determine the maximum limit.
That 1380W of devices should be about right for a 230W to 275W amplifier.
Sure enough, when I model it, it shows it can drive a 6ohm speaker load.
The rule being.
Multiply the maximum rated output power by that "factor" to determine the total device power rating that should be used for reliable operation at more than ordinary domestic duty.
If you want 600W of maximum power into your rated speaker impedance then provide ~ 3000W to 3600W of device power rating.
8pr of 200W devices is 3200W. 8pair is in the ballpark.
Now you must prove to yourself that 8pair is correct for that 600W of maximum output power. You can either model it and determine from experience with your model that it is likely to work or you can destructively test it to determine the maximum limit.
from post7, you can see that 1380W is short of 5 to 6 times 300W.
That 1380W of devices should be about right for a 230W to 275W amplifier.
Sure enough, when I model it, it shows it can drive a 6ohm speaker load.
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4 to 6 times that 450W max power rating.
If your plan to use 100W mosFETs then 4 * 450W = 1800W of FET devices, 9pr will do a 450W amplifier.
If you plan to use 250W BJTs then 5to6 * 450 = 2250 to 2700W of BJT devices, 4½pr to 5.4pr. try modeling or measuring 4pr and 5pr and 6pr to see which are likely to be reliable.
If your plan to use 100W mosFETs then 4 * 450W = 1800W of FET devices, 9pr will do a 450W amplifier.
If you plan to use 250W BJTs then 5to6 * 450 = 2250 to 2700W of BJT devices, 4½pr to 5.4pr. try modeling or measuring 4pr and 5pr and 6pr to see which are likely to be reliable.
Safe operating area - Wikipedia, the free encyclopedia
imho if the voltage does not exceed the second breakdown then
Maximum power transfer theorem - Wikipedia, the free encyclopedia
each rail with pure resistive load.
imho if the voltage does not exceed the second breakdown then
Maximum power transfer theorem - Wikipedia, the free encyclopedia
each rail with pure resistive load.
VibroKing$, perhaps you need to look at schematics around the forums and see what numbers of devices are used on real commercial and DIY amplifiers. If you count them, I think you'll find these numbers about correct. Manufacturers don't just throw more parts in for fun. They are necessary to cope with real, highly reactive loads, not just DC under laboratory cooling conditions.
Let's consider something familiar like a simple Hifi amp, with a single 150W transistor pair. You won't find 2SC5200/A1493 designs specified over 80W/8R. 100W designs use 2 pairs. Perhaps there are good reasons for this?
Let's consider something familiar like a simple Hifi amp, with a single 150W transistor pair. You won't find 2SC5200/A1493 designs specified over 80W/8R. 100W designs use 2 pairs. Perhaps there are good reasons for this?
Perfect, that is why I specified theoretical with pure resistive loadVibroKing$, perhaps you need to look at schematics around the forums and see what numbers of devices are used on real commercial and DIY amplifiers. If you count them, I think you'll find these numbers about correct. Manufacturers don't just throw more parts in for fun. They are necessary to cope with real, highly reactive loads, not just DC under laboratory cooling conditions.
Let's consider something familiar like a simple Hifi amp, with a single 150W transistor pair. You won't find 2SC5200/A1493 designs specified over 80W/8R. 100W designs use 2 pairs. Perhaps there are good reasons for this?
reality 'is much more complex
sorry if I explained badly
but it is quite simple.. (theroretical with resistive load)
Amplifier Efficiency
tranformer with 60-0-60Vac = rectified around 80-0-80Vcc
Amp output on load 8Ohms = 400Wrms (class B 78.1% efficency) but amplifier need supply of 508W
and with 800Wsquarewave (100% efficency) amplifier need 800W
for stereo amplifier 400+400Wrms on 8 Ohms
at max power amps need 508x2W = 1020W
I believe that, for home use may be sufficient an 800VA transformer. (undersize)
for professional use better 1200..1600VA transformer.
I hope not to have been wrong calculations
@Tekko - your comment would apply to all those misleading assumptions.
@Shelah - Have you counted the number of output transitors in your damaged amplifier? The answer is already in your hands as you have the specification of the amplifier that did work. You also have AndrewT's correction and estimates for it. Perhaps he will confirm that if you post your findings and quote part numbers as marked.
NOTE: Some power transistors will be drivers and probably there will be at least one pair used to drive the output transistors - It may be the same type as the others even. Without a schematic it will be difficult to be certain but you may be able to see that some are not grouped with others or they are labelled in some different way. Please look, it will benefit your understanding too.
@Shelah - Have you counted the number of output transitors in your damaged amplifier? The answer is already in your hands as you have the specification of the amplifier that did work. You also have AndrewT's correction and estimates for it. Perhaps he will confirm that if you post your findings and quote part numbers as marked.
NOTE: Some power transistors will be drivers and probably there will be at least one pair used to drive the output transistors - It may be the same type as the others even. Without a schematic it will be difficult to be certain but you may be able to see that some are not grouped with others or they are labelled in some different way. Please look, it will benefit your understanding too.
This post details it all, as I recommend.http://www.diyaudio.com/forums/solid-state/210606-va-rating-3.html#post2987384
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