Hello everybody. I've been reading this forum whenever it came up in a Google search, and it seems to always have the most knowledgeable members.
I am planning to build a class D amp for a sub I am building, and I want it to be as cheap and powerful as possible. Therefore, I am planning on foregoing the power transformer and simply rectifying the wall voltage and using 120V for the supply rails. I will have a lower voltage power supply of course to power the IR IC's.
I haven't tried doing a class D project before so I will probably be on here a lot as my design progresses.
I recently ordered four Power Acoustik 10" 800 watt RMS subs from amazon.com:
http://www.amazon.com/Power-Acousti..._2?ie=UTF8&s=automotive&qid=1223090994&sr=8-2
I think they are an incredible deal, especially due to the low shipping ($9) but it worked, they did ship them for that price. The resonant frequency of the speaker is a little high, but when $160 gets you 3200 watts RMS of speakers shipped to your door, I can't complain. Oddly, they say they have been on amazon.com for several years, but I can't find reviews of this speaker anywhere on the internet.
I figure if I make an amp that runs on 120V, I should have speakers I can plug directly into the wall. There are a few YouTube videos of people doing that, but they are deliberately trying to blow their speakers. I figure, however, that if I wire up these speakers as an 8 ohm total load, 120V RMS should put out 1800W RMS. These speakers can handle 3200W RMS total, and therefore should take it no problem.
I kind of feel like there will be more voltage there though. With a full bridge layout, does the speaker just see a max of the supply voltage in alternating current form, or is it twice the max? A full bridge is constantly reversing the supply rails to the speaker. If I use a 120V supply rail, can the speaker potentially see 240V RMS? I guess I don't really understand how a half bridge works; to me it seems like kind of a stupid idea.
So my questions are: Did I do my calculations correct? Can you apply Ohm's Law to alternating current like that, or is it an integration problem? Also, is designing a Class D amplifier with no power transformer a retarded idea, or an awesome idea? And, with a full bridge layout, is the speaker really seeing 120V RMS, or 240V?
Thanks for your help.
μH
I am planning to build a class D amp for a sub I am building, and I want it to be as cheap and powerful as possible. Therefore, I am planning on foregoing the power transformer and simply rectifying the wall voltage and using 120V for the supply rails. I will have a lower voltage power supply of course to power the IR IC's.
I haven't tried doing a class D project before so I will probably be on here a lot as my design progresses.
I recently ordered four Power Acoustik 10" 800 watt RMS subs from amazon.com:
http://www.amazon.com/Power-Acousti..._2?ie=UTF8&s=automotive&qid=1223090994&sr=8-2
I think they are an incredible deal, especially due to the low shipping ($9) but it worked, they did ship them for that price. The resonant frequency of the speaker is a little high, but when $160 gets you 3200 watts RMS of speakers shipped to your door, I can't complain. Oddly, they say they have been on amazon.com for several years, but I can't find reviews of this speaker anywhere on the internet.
I figure if I make an amp that runs on 120V, I should have speakers I can plug directly into the wall. There are a few YouTube videos of people doing that, but they are deliberately trying to blow their speakers. I figure, however, that if I wire up these speakers as an 8 ohm total load, 120V RMS should put out 1800W RMS. These speakers can handle 3200W RMS total, and therefore should take it no problem.
I kind of feel like there will be more voltage there though. With a full bridge layout, does the speaker just see a max of the supply voltage in alternating current form, or is it twice the max? A full bridge is constantly reversing the supply rails to the speaker. If I use a 120V supply rail, can the speaker potentially see 240V RMS? I guess I don't really understand how a half bridge works; to me it seems like kind of a stupid idea.
So my questions are: Did I do my calculations correct? Can you apply Ohm's Law to alternating current like that, or is it an integration problem? Also, is designing a Class D amplifier with no power transformer a retarded idea, or an awesome idea? And, with a full bridge layout, is the speaker really seeing 120V RMS, or 240V?
Thanks for your help.
μH
Inductor128 said:
This is potentially lethal and a "forbidden" subject on this forum. This thread will probably be closed.
From one Portlander to another, DON'T!
Atleast use an isolation transformer to isolate you from the mains wiring. What you propose is *very* dangerous.
Atleast use an isolation transformer to isolate you from the mains wiring. What you propose is *very* dangerous.
I've done this with tube amps (220V mains). NOT A GOOD IDEA. 
All I killed was my CD player, but it could have been me or my kid. Stay away.
All I killed was my CD player, but it could have been me or my kid. Stay away.
Hi, Inductor128,
This is a very dangerous and lethal practice. Please don't even try it.
This thread will be closed now.
This is a very dangerous and lethal practice. Please don't even try it.
This thread will be closed now.
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