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Old 20th May 2002, 10:14 PM   #1
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Default Big Honkin' Amp Design - Help Me! (Nelson?)

I have two transformers for 12V 40A power supplies, and they're just sitting there.

Here's my thought - hook them back-to-back for an amp with ~120v rails (120V-12V-12V-120V). But, this is quite a bit higher than anything I've ever worked with.

Now, the questions:
- I really like the Zen designs, but which would be best for something like this?
- Which output FET's would be be best (and how many)?
- What would the power output be (and rail voltage, so that power supply caps can be chosen)?
- What other precautions would there be, when working with these large voltages?
- What kind of mechanical design? (The xfrmrs are 25lbs each)

Thanks!
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Old 20th May 2002, 11:30 PM   #2
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I don't understand how you hook them up back-to-back
to get 120 V rails.
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Old 20th May 2002, 11:48 PM   #3
JoeBob is offline JoeBob  Canada
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I think he means use one to bring it down to 12V, then the next one in reverse to bring it back up to 120V. At least thats what it sounds like. Now why he'd want to do such a thing is beyond me...
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Old 21st May 2002, 12:03 AM   #4
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There have been several threads on monster amps. Start poking at the search button until you fall into one.
Personally, given transformers like that, I'd start running a bridged circuit (lower rails, lotsa bias). In fact, I'd love to get my hands on something like that for a pair of Aleph-X amps...

Grey
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Old 21st May 2002, 01:54 AM   #5
PassFan is offline PassFan  United States
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Default You've got to be kidding

You realize that you have the same voltage in as you do out. Transformers are used to change one voltage to another voltage. If you want 120volts just use the wall.
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Old 21st May 2002, 01:59 AM   #6
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Passfan
transformerless amp...

Thers a little kilowatt in you?
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Old 21st May 2002, 02:25 AM   #7
PassFan is offline PassFan  United States
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Now I'm not an advocate of that but to each his own. Looking at his diagram (120-12 -12 -120) just struck me as the obvious. I thought it was kind of funny, and I don't say that to be poking fun at anyone. Maybe he was going for some Isolation with that. I don't know. Is Kilowatt still alive? If he is I bet he's running really cool round about now.
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Old 21st May 2002, 09:14 AM   #8
djk is offline djk
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If the transformers are from a 12V 40A regulated supply they will be about 28VCT.Wire the two secondaries in series and you will have 56VCT.Rectified and filtered this will be +/- 40VDC.A bridge amp off this supply will be 400W/4R.
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Old 21st May 2002, 10:25 AM   #9
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Exclamation Using transformerless supply

Hi Passfan/Skippy,
<B>NEVER</B> I repeat <B>NEVER</B> use a audio circuit directly connected to the walloutlet. This is asking for disaster!!!
Your power amplfier will be lethal!
See Horowitz and Hill, the Art of Electronics $ 6.12.
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Old 21st May 2002, 11:04 AM   #10
djk is offline djk
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"NEVER I repeat NEVER use a audio circuit directly connected to the walloutlet. This is asking for disaster!!!
Your power amplfier will be lethal! " I tried telling that to JasonL and the others at 'Switching amplifier', but they all seem bent on earning the Darwin Award with that Popular Electronics death wish. I hope their life insurance policy is paid up.
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