1kW MOSFET amplifier

[Kilowatt]

Does anyone have any insite on my schematic here? Djk? I heard you were a schematic design guru. Does anyone think this thing could possibly be close to something that will work?

There's alot of you that I haven't heard from in a long time. It seems almost like some of the smartest people on this forum tend to ignore any threads that have the name "Kilowatt" in them. That hardly seems fair, but I refuse to change my alias just to get design help. Maybe I'm just being paranoid, I hope so.

Anyway, I'd just like to get my circuit figured out, and I confess to not being quite smart enough to do so by myself, at least not yet.

[SteveG]

Anyway, I'd just like to get my circuit figured out, and I confess to not being quite smart enough to do so by myself, at least not yet.

OK, so let me get this straight... You are going to build an off-line 36000 watt amplifier, and you aren't smart enough to design it?! Sounds a little bit risky (insane!). I'm still not with you on why you need this much power (which some outdoor concert venues don't even have).
And now, your getting on here practically demanding help? What's the point? You probably won't be alive long enough to enjoy your amp anyway!
Forget it... I just wasted how many keystrokes?

[Kilowatt]

Ah, I see. You probably don't follow my thread (you should know full well by now what this thing is for, what is envolved, how I'm doing it, and that I'm not going to kill myself with it, although you'd probably be relieved if I did), but I have obviously gotten far enough to work up a schematic. Someone else awhile back did that very same thing (came up with a schematic and posted it) and got lots of advice on how to improve the thing, but when I try it... you know. I guess I screwed up big time in that last post too, as I actually can probably do it, I just wanted some other technical insite. I see I won't get it, not from the likes of you, so I guess I should just go get some CAD software and work out my own problems all by myself. This site is here for people to help each other, but apparently If I need it, I have no business here in your opinion. It's nice to feel so welcome.

[mrfeedback]

Hey, Kilowatt is still alive !.

Eric.

[SteveG]

Hold on now, Kilowatt... hold on.
I have been following your thread. I know about the massive array of subwoofers, about how you want 140db, oh, and how you changed your mind- you just want as many db's as 7200 watts will give you. And, I know how a lot of people with more experience and a hell of a lot more common sense have told you (in not so few words) that this is a pointless and dangerous project. I know that you are dead set on overkill, and I know that there is no point in trying to get it through your thick skull that you will never need this much power (watt was it, 7200 watts? )
Why am I following it?
Because I think it is an interesting challenge to design an amp that big, and I think that designing for discussions sake is good food for thought.I just think you are either extremely immature, or just plain insane to actually consider building it! You don't even seem to know why you need this much power.
Take it from someone in his late 20's who has played drums for the last 18 years- you don't want to mess up your hearing, because you can't get it back!
If you want that much intensity, go hang out at the airport, or watch some top fuel dragsters.

As far as this site goes, I do believe that it's about audio- not the design of (as someone already acurately put it) earthquake simulation. Have you ever even been around 140db?
Give me a break! If you want to whine about why no one is helping you design your death machine, you will have to excuse me for feeling no sympathy. If by "the likes of me" you mean rational, then maybe you should go play with your simulator- at least until you're ready to listen to someone who isn't feeding your ego-driven ,closed-minded, pointless waste of time and server space. The CAD software won't work out the problems you have.
Only the time to learn a little temperance. No one is trying to knock you down for your lack of knowledge. Most here do want to help. The one here that is wrong is you, and only you. You refuse to listen. Do you really think so many people are against you? Why? You've got some kind of martyr syndrome happening here. The only really awful thing is that you actually may end up dying for your cause, and yes, I will be very sorry and not at all relieved.
By all means, if you want to ruin your hearing, then go for it. If you want to kill yourself, I won't be blamed for it. But consider that there are a lot more important things in life than having the biggest and baddest subwoofer in the world. Try finding a worthwhile mountain to climb, and for all of our sake quit whining when we won't participate in such foolishness!

[mrfeedback]

Let him spend far too much money, let him electrocute himself, let him cook his ears, let him annoy the neighbours, let him replace hundreds of dollars of bits each time it goes splatt, let him blow the gig when the one mission critical amp dies mid show,
......and then we can all say " I told you so !."

Eric.

[Kilowatt]

Well, quite a speach indeed, and, mrfeedback, if I were you, I wouldn't take on that attitude you seem to have about all this, it's not ethical if your so sure I'm going to go through hell if I do this.

Now, first of all, I never planned to be around that 140+dB, the system would be at some distance when at those volume levels, and depending on that distance, I would wear ear protection. I'm not quite stupid enough to stand in front of such a collosal SPL source. Also, even at low volume levels, due to tremendous headroom, it would sound wonderfully full and powerful (so I've heard) which is another incentive. Keep in mind this is an audiophile quality amp, not just an earthquake simulator, all though I'm sure earth-shaking bass would be no problem for 12 Eminence 15" subs. If all I wanted to do was be an egotistic badass, I'd be using car audio technology, where sound quality is of no importance, but I could probably go louder.
I do like overkill, but I also know enough to be safer that you might think with something like this in my posession.

Now, if you are still so sure that this project is nothing but a killing, deafening, destructive beast to be banned forever and never attemted under any circumstances whatsoever, especially by someone like myself, and that I'm an ignorant, immature, thick headed jerk who just want's recognition, what do you think I should do? Honestly now, should I continue, or should I just dump the project, throw my chassis in a junk yard or use it for scrap aluminum, delete my schematics and CAD files of it, and tell everyone (here and elsewhere) "oh, never mind, I guess I won't make the amp after all, I'm too dumb." Basically, Crown, QSC, Pass Labs, and Harrison Labs can do it, but I'd better not because I'll kill myself. Isn't that right? I'd just like to know what you think I should do, I'm in this pretty deep, and apparently I'm on the road to hell and everyone knows it but me. Should I forget about it? I don't see any other options.

What about the people that have told me it's ok? Are they thick headed fools too? Are they secretly waiting to here my news of how all that's left of my house is a 10 foot deed crater and I'm deaf, blind, and out a $20,000 system?

Would I be stupid to go on with this at any time, or do you think I can pull it off?

[SteveG]

Also, even at low volume levels, due to tremendous headroom, it would sound wonderfully full and powerful (so I've heard) which is another incentive

Headroom is one thing, but you have to know this is above and beyond absurd. I have heard electrostatics with 400 watts per channel, and they reached dynamic levels that were realistic, and were not out of steam. It sounded like <i>live music</i>, which is the point, or so <i>I've</i> heard.

Now, if you are still so sure that this project is nothing but a killing, deafening, destructive beast to be banned forever and never attemted under any circumstances whatsoever, especially by someone like myself, and that I'm
an ignorant, immature, thick headed jerk who just want's recognition, what do you think I should do? Honestly now, should I continue, or should I just dump the project, throw my chassis in a junk yard or use it for scrap aluminum, delete my schematics and CAD files of it, and tell everyone (here and elsewhere) "oh, never mind, I guess I won't make the amp after all, I'm too dumb." Basically, Crown, QSC, Pass Labs, and Harrison Labs can do
it, but I'd better not because I'll kill myself. Isn't that right? I'd just like to know what you think I should do, I'm in this pretty deep, and apparently I'm on the road to hell and everyone knows it but me. Should I forget about it? I
don't see any other options.

Well, part of being a mature adult and a good designer is recognizing when your on the wrong track, admitting that maybe you didn't think it through clearly, and redirecting your efforts. There is a big difference between being ignorant, and acting like a jerk. And, yes, I do think you are doing this for recognition. There is no other point to doing it! Others have given you examples of systems that would meet your requirements that were realistic and safe. You're obviously not dumb, but you are making an *** of yourself by not letting go of this.
You obviously know better than to say "throw it all away"! Come on- there are a lot of things you can do with the parts you have, and you know it! If you're really serious about maximum SPL, why don't you start out by building (out of the parts you have) an 800 or 1000 watt p-p Class B Mosfet amp with a transformer, like one of the aussieamp designs. Then, hook it up to your array of woofers, and see what it will do. I will bet that you will be impressed! That many woofers will guarantee effortless dynamic bass with low distortion. But no, you are on this rebel kick, and you won't give it up!

What about the people that have told me it's ok? Are they thick headed fools too? Are they secretly waiting tohere my news of how all that's left of my house is a 10 foot deed crater and I'm deaf, blind, and out a $20,000 system?

You would be surprised at the number of people out there who are only happy when someone else is miserable, or who like to get off on seeing someone else fail. It's a game to some people. Honestly- I don't want to see you hurt, or fail, if you can believe that. You're obviously a smart guy, and a hard worker, and yes, it is possible that you could pull it off. Are you willing to bet your life on it?
What will you end up with when you're done, even if you do? Most likely a grossly overpowered system that isn't musically satisfying. Sure, your ego will be stroked, but so what! If you take a good honest look at your posts, you will see that you are looking at this totally backwards- "I want to build a XXX watt amp with XXX" instead of, I have such and such room, and would like to acheive a musical design. I will need these speakers, which could work well with this, this, and this type of amp. I need this much power to guarantee full dynamic range at realistic levels. I prefer this type of sound, and the best way to get there is... etc. etc. etc.
There is nothing wrong with re-thinking your design. No one will think your wimping out, and if they do, screw them anyway! Why don't you take a break and reconsider what your realistic goals should be. You will gain a lot of respect from those who understand that music is more than shaking the walls, and they will start discussing designs with you.

[Kilowatt]

Well, looking at it that way, I actually do have almost ulimited room, that's the truth. What I'm trying to accomplish here, I think you know, is a system that, outside, will leave it's listeners totally in awe at it's superb musical clarity and also raw power. I'm sure you know what It's like to hear something like that- very impressive. I also want to build it myself, and design it too. With my 7200W amp design, I figured there would be plenty of amp there for that, if designed well, even at great distance, with tremendous headroom, like a huge PA system with hifi quality.

When I got the idea for this, I was much younger and less knowledgeable than I am now, I figured "hell, 7200W ought to do, that's about as much as I can sqeeze out of the biggest standard size single phase outlet, and the math is convenient, so that's what I'll use." As I learned more, I saw no reason to give that up or to rethink it, until now. Actually, I really would like 8x900W into 12 ohms, and here's why. 12 is divisible by a great number of things, I can put 3 4ohm speakers in series, two 6ohm speakers in series, 4 dual 3ohm speakers in series-parallel, 6 8ohm speakers in series-parallel, and much more. The amp could also run into 8 or 16 ohms. This makes the amp very versatile. The other reason is of course the infamous line power. It is very convenient that 240VAC CT, as is readily available, makes a nice +/-160-170V power supply, which will give me that 900W into 12 ohms. You can see why someone would be tempted to do this, I'm sure.

Now, you might agree, or maybe not, that 7200W isn't actually all that ubsurd, for many PA systems do it. It can only do maybe 17 or 18dB more than a 1000W amp . I have of course heard that "you'd only have one amp, if it fails, you'd be screwed." That is actually not true, keep in mind that this amp is actually 8 amps, only sharing a cooling system and breaker, and some switches and stuff, which are unlikely to go (You obviously know that breakers don't trip very quickly, and even if I draw a 200A peak, the breaker won't trip, If it does, it's not hard to reset.

Many people seem to think that the main reason I shouldn't do this is because I don't have a power transformer, but I think that's been covered, and I think to this day that it's not so dangerous as it might seem.

I don't know how much this pertains, but I once read a supposedly true story about some guys who got some JATO bottles (Jet Assist Take Off, used to give military cargo jets an extra boost during takeoff to reduce needed runway) from a junkyard (one of the guys' father bought various junk at auctions, it is illegal to keep any military stuff of this sort if you end up with it, but these guys did), and put one of them on the back of a car body welded to an old rail car from an abandoned mine and fired it off. They actually would have rode in it if it hadn't crashed during their preliminary unmanned test. You get my point. We all do some things just because they seem like the cool thing to do.

I suppose I could rethink a few things, like power transformer, speaker impedence, maybe even power level, but what would it help? Speaker sensitivity is something that manufactures don't usually tell the truth on, so I don't know how I can really calculate what I need. I've got to start somewhere. Have you seen project 20kW? Is that guy a crazy fool? Even if I don't do 7200W, what's wrong with the Kilowatt Amp, that 900W channel? Amplifier design is what I'm trying to do as much as anything here, and I don't see why I can't make it sound great, with modern methods. What makes you think it won't be musically satisfying?

So, where do you think I should redirect my efforts to? I want an enormous, great sounding system (who doesn't) that I designed and built myself. Is there a better way? If your thinking it's a waste of money, It might cost about $10,000-$12,000, some people would spend that much on a 2x60W tube-based system with 1% THD.

[paulb]

Originally posted by Kilowatt
...I once read a supposedly true story about some guys who got some JATO bottles ... and put one of them on the back of a car body welded to an old rail car from an abandoned mine and fired it off. They actually would have rode in it if it hadn't crashed during their preliminary unmanned test.

The way I heard the story is somebody killed themself doing it. This story started the whole Darwin awards thing.
Whether Kilowatt builds this thing or not, it could be an interesting design to follow. I'm not sure why you folks are so upset he's considering this. We've cautioned him about the safety issue.
And Kilowatt - just don't take anybody with you when you go.