1kW MOSFET amplifier - Page 4

Kilowatt · 20th January 2002, 08:27 AM

Any idea how big of a compressor I would need to cool a 7200W class B MOSFET amp as an alternative to huge heatsinks?

AudioFreak · 20th January 2002, 08:43 AM

Kilowatt..... clearly quality is not the main concern here as Class B has rather large distortion figures..... you could also try Class G which is more efficient than Class AB but should sound better than Class B

Kilowatt · 20th January 2002, 08:48 AM

Well, class AB, whatever. I think perhaps Randy Sloan has a different opinion on what class AB means.

Quality is of very great concern, I am hoping for distortion figures less than 0.1%.

PassFan · 20th January 2002, 03:58 PM

Kilowatt:
Randy Sloan is knowlegable enough to understand the theory behind the amplifier classes as well as the rest of us. To form an opinion about something as basic a rule as this, and then put it out there for all to see would not be very smart. I would have to give Randy more credit than that. Perhaps you've taken him out of context. I don't think that finding a circuit with less than 0.1% distortion should be a problem. However, at 7200watts the problem will be in a large enough power supply to drive it without distortion and how to move it. I see on another thread you may build seperate amps at 900 watts a channel. These supplies would be a more realistic goal. Good luck.

Kilowatt · 20th January 2002, 08:13 PM

The design of this amp will be based very much on what Randy Sloan has written, he's very knowledgeable, he calls it's class B, it has very low distortion (.0038%).

Anyway, the 7200W amp will have 8 x 900W channels. I want to cool it with a compressor like from an old freezer. I want to know how to figure out how big of a compressor I would need to achieve a certatin thermal rating for my heatsinks.

JoeBob · 20th January 2002, 09:25 PM

Well, just figure out how many watts of heat your amp will be putting out and then get ahold of a compressor rated to handle that amount of heat. Be warned though, freezer/fridge compressors aren't meant to handle a constant load of heat, they're meant to cool down a small amount of heat and then keep that object cold. You might be better off using a dehumidifyer compressor, they're more "powerfull" then fridge ones usually. But even then, I'm not sure how many watts they can handle, I just know I've used one to freeze an AMD PC processor pretty well (but they're obviously not all the same). With large amounts of heat you'd be much better off going H2O cooling, and if it really is alot of heat (I don't know how much heat would get put off by a 7200W amp) you could easilly go with several sperate loops, say a heat exchanger, pump and radiator per channel or per 2 channels...

Kilowatt · 20th January 2002, 09:55 PM

A 7200W class B MOSFET amp would dissipate maybe 4000W of heat, probably not much more in a worst-case scenerio. Would that be too much for a refridgerator compressor? I'm thinking a water or antifreeze cooling system would be bulky compared to a compressor, and would not be able to lower the temperature as much. Is this true?

JoeBob · 20th January 2002, 10:22 PM

Well, water would work better then antifreeze, but 60% H2O and 40% methanol in a closed loop system is a very good way to go if you don't want stuff to grow (I gather that's why you said antifreeze). And yes, it could be rather bulky, but if done well you could probably minimize space required. But 4000W is much too much for a freezer compressor, I've had a fridge compressor choke on 200W of heat. If you really want to go with the compressor route you'd need lots of little freon compressors (maybe one per channel, if not more, again it depends on how many watts they can handle), which would be alot bulkier and louder then the H2O rig, and you'd have to worry about condensation and insulation.

The only reason you'd need a compressor would be to get something cold (ie below ambient). If you want to cool something down to somewhere above ambient (or very close to ambient) there are much more efficient ways of doing it. I don't know maybe you need you're amp below zero, but I truly doubt it for some reason

.

Kilowatt · 20th January 2002, 10:32 PM

Actually, I said antifreeze in case the amp will ever be outside when it's below freezing, but 40% methanol would also keep it from freezing, and nothing would grow in it.

PassFan · 21st January 2002, 02:08 AM

Have you thought of what this thing is going to weigh? 7200 watts of output + 4000 watts wasted heat is going to mean about 12000 watts of power supply. A 2000 watt tranny can weigh in around 30 lbs. How are you going to carry it. Designing it to be rackmountable would be ideal. Maybe refigure how you set up your cabinets to your amps to create a more weight efficient setup? Just a thought, your the one that has to carry these things. Coming from a former musician/personal roadie, it might be worth it at first but your going to get tired of lugging these things around. Make it easy on yourself right up front. Calculate the weight, and set it up with wheels in road cases with a not to exceed weight. You'll thank yourself for it later.

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20th January 2002, 08:27 AM	#31
Kilowatt diyAudio Member Join Date: Nov 2001 Location: Harlowton, MT, USA	Any idea how big of a compressor I would need to cool a 7200W class B MOSFET amp as an alternative to huge heatsinks?

20th January 2002, 08:43 AM	#32
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	Kilowatt..... clearly quality is not the main concern here as Class B has rather large distortion figures..... you could also try Class G which is more efficient than Class AB but should sound better than Class B

20th January 2002, 08:48 AM	#33
Kilowatt diyAudio Member Join Date: Nov 2001 Location: Harlowton, MT, USA	Well, class AB, whatever. I think perhaps Randy Sloan has a different opinion on what class AB means. Quality is of very great concern, I am hoping for distortion figures less than 0.1%.

20th January 2002, 03:58 PM	#34
PassFan diyAudio Member Join Date: Aug 2001 Location: Central FL	Kilowatt: Randy Sloan is knowlegable enough to understand the theory behind the amplifier classes as well as the rest of us. To form an opinion about something as basic a rule as this, and then put it out there for all to see would not be very smart. I would have to give Randy more credit than that. Perhaps you've taken him out of context. I don't think that finding a circuit with less than 0.1% distortion should be a problem. However, at 7200watts the problem will be in a large enough power supply to drive it without distortion and how to move it. I see on another thread you may build seperate amps at 900 watts a channel. These supplies would be a more realistic goal. Good luck.

20th January 2002, 08:13 PM	#35
Kilowatt diyAudio Member Join Date: Nov 2001 Location: Harlowton, MT, USA	The design of this amp will be based very much on what Randy Sloan has written, he's very knowledgeable, he calls it's class B, it has very low distortion (.0038%). Anyway, the 7200W amp will have 8 x 900W channels. I want to cool it with a compressor like from an old freezer. I want to know how to figure out how big of a compressor I would need to achieve a certatin thermal rating for my heatsinks.

20th January 2002, 09:25 PM	#36
JoeBob diyAudio Member Join Date: Nov 2001 Location: Montreal, Canada	Well, just figure out how many watts of heat your amp will be putting out and then get ahold of a compressor rated to handle that amount of heat. Be warned though, freezer/fridge compressors aren't meant to handle a constant load of heat, they're meant to cool down a small amount of heat and then keep that object cold. You might be better off using a dehumidifyer compressor, they're more "powerfull" then fridge ones usually. But even then, I'm not sure how many watts they can handle, I just know I've used one to freeze an AMD PC processor pretty well (but they're obviously not all the same). With large amounts of heat you'd be much better off going H2O cooling, and if it really is alot of heat (I don't know how much heat would get put off by a 7200W amp) you could easilly go with several sperate loops, say a heat exchanger, pump and radiator per channel or per 2 channels...

20th January 2002, 09:55 PM	#37
Kilowatt diyAudio Member Join Date: Nov 2001 Location: Harlowton, MT, USA	A 7200W class B MOSFET amp would dissipate maybe 4000W of heat, probably not much more in a worst-case scenerio. Would that be too much for a refridgerator compressor? I'm thinking a water or antifreeze cooling system would be bulky compared to a compressor, and would not be able to lower the temperature as much. Is this true?

20th January 2002, 10:22 PM	#38
JoeBob diyAudio Member Join Date: Nov 2001 Location: Montreal, Canada	Well, water would work better then antifreeze, but 60% H2O and 40% methanol in a closed loop system is a very good way to go if you don't want stuff to grow (I gather that's why you said antifreeze). And yes, it could be rather bulky, but if done well you could probably minimize space required. But 4000W is much too much for a freezer compressor, I've had a fridge compressor choke on 200W of heat. If you really want to go with the compressor route you'd need lots of little freon compressors (maybe one per channel, if not more, again it depends on how many watts they can handle), which would be alot bulkier and louder then the H2O rig, and you'd have to worry about condensation and insulation. The only reason you'd need a compressor would be to get something cold (ie below ambient). If you want to cool something down to somewhere above ambient (or very close to ambient) there are much more efficient ways of doing it. I don't know maybe you need you're amp below zero, but I truly doubt it for some reason .

20th January 2002, 10:32 PM	#39
Kilowatt diyAudio Member Join Date: Nov 2001 Location: Harlowton, MT, USA	Actually, I said antifreeze in case the amp will ever be outside when it's below freezing, but 40% methanol would also keep it from freezing, and nothing would grow in it.

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21st January 2002, 02:08 AM	#40
PassFan diyAudio Member Join Date: Aug 2001 Location: Central FL	Have you thought of what this thing is going to weigh? 7200 watts of output + 4000 watts wasted heat is going to mean about 12000 watts of power supply. A 2000 watt tranny can weigh in around 30 lbs. How are you going to carry it. Designing it to be rackmountable would be ideal. Maybe refigure how you set up your cabinets to your amps to create a more weight efficient setup? Just a thought, your the one that has to carry these things. Coming from a former musician/personal roadie, it might be worth it at first but your going to get tired of lugging these things around. Make it easy on yourself right up front. Calculate the weight, and set it up with wheels in road cases with a not to exceed weight. You'll thank yourself for it later.