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Old 19th June 2004, 04:27 AM   #1
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Angry is transformerless amp with 170v rails diyable?

I was thinking that instead of spending money on a huge transformer, it would be easier to rectify 120v, which would give +/- 170v rails. Would it be possible to build an amp (a class d would be nice) that will run off of 170v rails? The amp would put out about 15kw max at 2 ohms.
Old 19th June 2004, 04:35 AM   #2
sam9 is offline sam9  United States
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This an extremely dangerous idea. It is likely to kill you sooner or later. Probably sooner.
Old 19th June 2004, 04:40 AM   #3
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i know that its dangerous, but is it diyable?
Old 19th June 2004, 04:52 AM   #4
Tim__x is offline Tim__x  Canada
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Even if it wasn't for the isolation problems, with rails that high you'd be likely to instantly blow circuit breakers and start fires with almost any load. I highly reccomend NOT trying this.
Old 19th June 2004, 04:56 AM   #5
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It's as diyable as ....sticking a rag in your gas tank, lighting it up, and using the light eminating from it to shave by.

It "could" be done..Even if you survived the blast the fine they'd give you for it would far outdo the cost of a transformer, which you can easily recycle from something else free of charge anyway.
Old 19th June 2004, 05:05 AM   #6
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At least you will be having a good time on your way out...

Seriously, it is very dangerous to play with 50VDC, and 170VDC is lethal. When DC bites you, it won't let you go, and good luck at that point!

It does not sound like you know enough to attempt this project if you do not know that an isolation transformer is another MUST to stay reasonably safe. Also, where do you plan to take your 0V from? Earth ground?

Secondly, where do you acquire 15kW speakers? And you are going to need to handle 85A (On a side note: this current comes from where? Your surge-protector and breaker rated at 10A max?) at that voltage to get your 15kW...that is some current right there, and several dozen transistors if you go that route. The heatsinks for those alone will have to dissapate a TON of would need giant ones, class D or not! Lets just say the amp would be 90% efficient (class D) 5kW there is 500W missing...and where do you think that goes? Class AB at below 80% is even worse.

Also, there is the *small * task of designing a class-D (or any) amp of that magnitude.

If you were going to actually build an amp this big you would need so much $$$ that the transformer would be only a small blip on the radar.

Bottom line: don't try it.

Old 19th June 2004, 07:18 AM   #7
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Default Re: is transformerless amp with 170v rails diyable?

Originally posted by xplod1236
it would be easier to rectify 120v, which would give +/- 170v rails.
You might as well just commit suicide... i think the other posters have made it very clear that this is not safe.

This subject is a forbidden one on diyAudio (hence i'm going to close the thread).

I repeat -- this is not safe.


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