PassFan,
The amp is Class B or AB so will not have much in the way of quiescent dissipation........
Also the supply is transformerless and each 900W amp will have a seperate power supply .....
The amp is Class B or AB so will not have much in the way of quiescent dissipation........
Also the supply is transformerless and each 900W amp will have a seperate power supply .....
Actually, it will have one power supply for all 8 channels. It will have a 60A breaker as an on/off switch, 4 150A discrete rectifier diodes, at least 8 200V, 31,000uF filter caps (not much for a brute like this, I know, but it will have a high PSRR, and besides, those caps are huge and expensive), smaller electrolytics, film caps, two MOVs, 20W bleeder resistors (I'd hate to see those caps discharge into a screwdriver!! There wouldn't be a srewdriver left, I'd be seeing spots and have a ringing in my ears for a week!), and possibly two big inductors mounted in a compartment under the rest of the chassis.
I wonder how much tubing I'd need in the heat exchanger for this thing?
I wonder how much tubing I'd need in the heat exchanger for this thing?
thats not gonna be anywhere big enough for this amp kilowatt.. on transients this amp is gonna load down like crazy if it doesnt have heaps and heaps of low resistance capacitance in the power supply and because all channels will peak @ the same time, the peak current draw will be in excess of 100A
KiloWatt, I don't know if anyone else has asked this exactly, but what are you going to use this thing for?? Simulating earthquakes, producing 5 hz tones at 140 db? This is a serious amount of power. Of course you could just be doing it for fun which is a good enough answer for me. But if you really need that much power, wouldn't it be cheaper to buy a comercialaly made amplifier setup? I know that a crown ce2000 is rated at 975 watts/channel into 2 ohms and they only cost about 550. Get 4 of these and you have your power requirements, it will only cost 2200 dolars for all 8 channels, all of the protection circuitry is built in, all of the cooling is built in, and to top it all off, there is a warrenty and they only wieigh about 40lbs each.
Not that I want to put a damper on the DIY spirit. Sometimes it is cheaper and wiser to go comercial. It's like designing a robot that can clean dishes when there are 200 dollar dishwashers for sale in every department store. But if this is a just for fun project, then good luck and take plenty of pictures for us all to see.
Not that I want to put a damper on the DIY spirit. Sometimes it is cheaper and wiser to go comercial. It's like designing a robot that can clean dishes when there are 200 dollar dishwashers for sale in every department store. But if this is a just for fun project, then good luck and take plenty of pictures for us all to see.
the problem with the above mentioned amp is that it produces 975W into 2ohms.... Kilowatt needs that kinda power into a 12ohm load.
Also, the 7200W amp by itself will not cost more than $1000 US to build, not including the outputs I'm likely to blow up, of course.
How much capacitance should the power supply for this have?
How much capacitance should the power supply for this have?
I won't, the power supply won't have a transformer. If you read this whole thread, you'd know that. AudioFreak said that just a few posts back.
He's going to use the transformer up on the Utility pole.
I posted an explaination earlier in this thread.
Phil
I posted an explaination earlier in this thread.
Phil
Yup, that's right, now, about how much capacitance would be recommended for the power supply? I think I'd need more if the amp had a lower supply voltage, but those 200V 31000 uF high grade, super low ESR, high ripple current caps are 3 1/2" in diameter by 5 5/8" tall and cost $182.75 each! Those caps are going to take up more space and more money than anything else in this amp. How many do you think I should have?
Hi Kilowatt,
This question is really dependent on the design of your amp. Some designs are more tolerant of ripple on the rails than others.
I have seen rules of thumb that recommend at least 10,000 uf per 100 watts of power and I have also see people use 50,000 uF on a 50 watt Class A amp. The problem with rules of thumb is that they usually don't scale very well when you change the magnitude of the problem.
I would think that 100,000 uF would be enough for a 2000 Watt amp that is not intended for Hi-fidelity, but I have never built one this big. The simple answer is build one amp and try different amounts of filtering to see how it performs.
Given how many amps you're planning on building you could buy enough to make a couple of amps and the buy the rest once you know for sure how many you are going to need.
I know you are dead set on doing this, but did you know you can buy a brand new QSC PLX-3402 amp that will deliver 1700 Watts per channel into a 2 ohm load or 3400 Watts bringed into a 4 ohm load for about $1200. I don't believe you are going to be able to buy the parts to make your amps for less than this.
In quantity you might even be able to get thyem for less than $1200.
Phil
This question is really dependent on the design of your amp. Some designs are more tolerant of ripple on the rails than others.
I have seen rules of thumb that recommend at least 10,000 uf per 100 watts of power and I have also see people use 50,000 uF on a 50 watt Class A amp. The problem with rules of thumb is that they usually don't scale very well when you change the magnitude of the problem.
I would think that 100,000 uF would be enough for a 2000 Watt amp that is not intended for Hi-fidelity, but I have never built one this big. The simple answer is build one amp and try different amounts of filtering to see how it performs.
Given how many amps you're planning on building you could buy enough to make a couple of amps and the buy the rest once you know for sure how many you are going to need.
I know you are dead set on doing this, but did you know you can buy a brand new QSC PLX-3402 amp that will deliver 1700 Watts per channel into a 2 ohm load or 3400 Watts bringed into a 4 ohm load for about $1200. I don't believe you are going to be able to buy the parts to make your amps for less than this.
In quantity you might even be able to get thyem for less than $1200.
Phil
Hopefully this amp will have a pretty high PSRR. I'll just get more caps as I need like you say.
Is there anywhere on the internet I can get giant caps like I'll need for less than what I mentioned in my above post? I would prefer new ones, I don't like the idea of getting used electrolytics.
Is there anywhere on the internet I can get giant caps like I'll need for less than what I mentioned in my above post? I would prefer new ones, I don't like the idea of getting used electrolytics.
If you know someone in the photographic processing industry, a good source of high voltage caps is available from the used disposable flash cameras ... the caps are usually 330V 120uF so you'll need alot of them .... try the local 1hr processing shop and ask kindly if you could have the used flash cameras... some shops send them back for recycling and may be reluctant but many just throw them in the bin.... just be warned that the cap is usually charged to just under 300V when you get the camera so be careful when you pull the back off...
I'd need thousands of those caps, it's not much of an option. I think it would be too much trouble to use anything less than about 10000uF each, but thanks anyway.
5000 of them? I refuse to wire 5000 little caps together 🙂 , and besides that, they are not all identical, so I would think that some of them would be destroyed much like if you try to wire up several BJTs in parallel with no resistors.
That's about 300,000uF per side, or about 20 of the big cans. Do you think that's about the right capacitance for this supply assuming fairly good PSRR? That would cost about $3800, not really an option. I need to find that kind of thing for cheaper! Anywhere I can get big caps, at least 200V, like that?
That's about 300,000uF per side, or about 20 of the big cans. Do you think that's about the right capacitance for this supply assuming fairly good PSRR? That would cost about $3800, not really an option. I need to find that kind of thing for cheaper! Anywhere I can get big caps, at least 200V, like that?
See you will face a few problems ... because you wont have a transformer in the power supply, now only do you have to be concerned about how much noise is on the rails, you've also gotta consider how much noise you'll be shooting back up into the mains..... i think you could have some very irrate neighbours if their TV reception suddenly goes down the toilet @ the same time that your amp starts making its presence know/heard/felt...
you've also gotta consider how much the rails will collapse under load and the line resistance ... all these things will have an effect on how much capacitance will be required.
most of the PA amps i've dealt with have used switching supplies i think ... tho they are a pain and murder to design properly, they certainly fix alot of the problems 🙂 in very high power non audiophile applications.
you've also gotta consider how much the rails will collapse under load and the line resistance ... all these things will have an effect on how much capacitance will be required.
most of the PA amps i've dealt with have used switching supplies i think ... tho they are a pain and murder to design properly, they certainly fix alot of the problems 🙂 in very high power non audiophile applications.
Killowatt,
Considering AudioFreak's words, you might consider to maintain this power supply caps with some charge, to reduce these "cool" efects over the mains when you turn on your "little" amps.
About how much capacitance you will need, the most important thing is to know something about the nature of the load of the power supply (class A 😀 , B, D etc) and its PSRR characteritics.
There is an rounded solution in the book Integrated Electronics by Milmann/Halkias wich might be enough for your very first approach on the question:
Vripple=Icc/(2*f*C) , for continuous loads.
Regards
Considering AudioFreak's words, you might consider to maintain this power supply caps with some charge, to reduce these "cool" efects over the mains when you turn on your "little" amps.
About how much capacitance you will need, the most important thing is to know something about the nature of the load of the power supply (class A 😀 , B, D etc) and its PSRR characteritics.
There is an rounded solution in the book Integrated Electronics by Milmann/Halkias wich might be enough for your very first approach on the question:
Vripple=Icc/(2*f*C) , for continuous loads.
Regards
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