the figures quoted are result of real world measurements across the load.
The only explanation would be supply regulation, as the DC voltage on the supply caps drops to about 85 volts under load...
The way Crown achieve power o/p approching 4 times the power o/p is because they use tightly regulated SMPS...
The only explanation would be supply regulation, as the DC voltage on the supply caps drops to about 85 volts under load...
The way Crown achieve power o/p approching 4 times the power o/p is because they use tightly regulated SMPS...
Aussieamps said:OK
Bridging works like this in theory.
You have an amplifier which has say a 2kw power supply.
Its power o/p into 8 Ohms is 100 watts RMS (28.4 VAC @ 3.55 Amperes RMS= 100.82 watts RMS)
If you bridge this same amplifier into an 8 Ohm load in theory you should get twice the voltage across the 8 Ohm load (56.8 VAC RMS @ 7.1 Amperes RMS = 403.28 Watts RMS)
Or 4 times the power o/p
If you then half the impedance or load on this bridged amplifier to say 4 Ohms. In theory you should get twice the o/p power again.
(56.8 VAC @ 14.2 amperes = 806.56 Watts RMS)
Which is 8 times the power o/p into 8 Ohms on an non-bridged amplifier or 4 times power o/p @ the same impedance of 4 Ohms.
Now this is assuming ideal amplifiers and power supplies with no losses what so ever
In practice this doesn't happen....
If you look at any commercial amplifier which operates in bridge mode, they only ever double their power o/p into any given load equal to the non bridged load...
My AV800 amplifier produces over 870 watts rms into 4 Ohms non bridged. In bridge mode it produce about 1600 watts rms into 4 Ohms with a 2KVA transformer. Into 8 Ohms bridged it produces about 870 watts. which is about double its power o/p into 8 Ohms of 450 watts RMS.
The only commercial amplifier that could possibly come close to 4 times the o/p power would be Crown amplifiers. Which use Grounded Bridge Technology and even then they a subject to power losses and produce 4 times the power o/p or greater by driving into impedances of 2 Ohms or less...
Another amplifier would be Krell and not even Nelson Pass amplifiers x1000 can produce 4 times the power o/p in bridge mode using just two single module amplifiers into 8 Ohms...
I am willing to be corrected here, But I just don't see it...
regards
Anthony Holton
I agree with the 1st part of that post but i would suggest you check your facts .... Pass X-1000 is a bridged monoblock before you start
also 2 such units are indeed very capable of producing 4000W into 8ohms .... that is 4x the output power of a single X-1000 into the same 8ohm load also the professional yamaha amps produce twice the power into twice the load in bridged configuration but are unable to produce 4 times the output into the original load because the power supply is current limited.Also, here's an example that proves that more than 2x the power is attainable using bridge mode (and it's not class D). This is the power ouput of Alpine's MRV-1507:
450W x 2 (4 Ohm Stereo) 1500 x 1 (Bridged 4 Ohm)
This is the max power, RMS is (they claim) 225W/900W respectively, which also proves the point, even if that 900W figure is a slight exaggeration.
Perhaps it is all in the power supply, an Anthony has suggested.
450W x 2 (4 Ohm Stereo) 1500 x 1 (Bridged 4 Ohm)
This is the max power, RMS is (they claim) 225W/900W respectively, which also proves the point, even if that 900W figure is a slight exaggeration.
Perhaps it is all in the power supply, an Anthony has suggested.
I agree it is hugely dependent on the capabities of the power supply .... also most the specs for car amps are voltage limited not current limited .... mind you, if your bridging 2 amps to achieve 4 times the power then each of them must supply only double that of their normal output.... with a BIG power supply and plenty of o/p devices, this shouldnt be too much to ask.... after all, this is the equivalent of running the amp into half the impedance ... upto a point, this is quite doable.
Aussieamps said:My AV800 amplifier produces over 870 watts rms into 4 Ohms non bridged. In bridge mode it produce about 1600 watts rms into 4 Ohms with a 2KVA transformer. Into 8 Ohms bridged it produces about 870 watts. which is about double its power o/p into 8 Ohms of 450 watts RMS.
regards
Anthony Holton
it appears we have misunderstood each other.... you say your AV800 can do 450W into 8ohms and 870W into 4ohms .... well if you bridge these amps into an 8ohm load then each will see the equivalent of 4ohms .... so each will produce 870W into the load ... giving a total of 1740W into the 8ohm load between the 2 amps .... this is almost 4 times the power of a single amp into 8ohms so it works quite nicely with theory ... sure i am willing to concede 30W loss per amp ... i just dont know how one of us didnt pick up on this earlier.... when bridging you'll have a minimum of 2 amps ...assuming 2 amps.... each produces the same voltage as they would have in non bridge config ... but because when one amp is + the other is - the voltage between them is double that of what a single amp would have produced on it's own.... so they are called upon to deliver twice the normal current ... which is the equivalent of running each amp into 1/2 the original load... now each amp has produced twice it's normal power but the voltage across the speaker terminals is doubled and so has the current so the speaker will get 4 times the power.... no bridging theory states that each single amp should have to produce 4 times the power into the same load .... only twice the power .... it is the total power into the speaker that goes up 4 fold compared to a single amp so if you have an amp rated for 2 x 100W into 8ohms, 2 x 200W into 4ohms then it should be rated 1 x 400W into 8ohms bridged ... sure, in practice it'll be a little less but that about does it.
So i stand by my earlier post ....
AudioFreak said:
in the above example, each amp is rated @ 300W into 8ohms so will give probably just less than 600W into 4ohms....now you have 2 such amps... if you bridge these into an 8ohm speaker then each will effectively see 4ohms and so produce just under 600W ... now each amp is making 600W into that load so there is 1200W into the load.... just like i originally stated it.
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.
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.
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.
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.
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...
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?
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.
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
.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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