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Old 10th January 2008, 05:02 PM   #71
luka is offline luka  Slovenia
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Hi

In mute it should hold up...And if you will test it in car, start with engine off, then on, but with lights on. This amp looks and means business nice job...

PS: that is a lot of wire , do you happen to know how much that was, length?
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Old 10th January 2008, 05:13 PM   #72
djQUAN is offline djQUAN  Philippines
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I hope it holds up. I'm having second thoughts if I would remove a turn off the trafo to drop the voltage a bit.

the voltage goes up to +/-68V when there is no load and input is about 14.5V just before the overvoltage trips and shuts the supply down.


how much wire? the amp now weighs a lot.

each primary is about 14" long, the secondary is about 9feet. those are estimates BTW. never thought about measuring them before winding. hehe
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Old 10th January 2008, 05:18 PM   #73
luka is offline luka  Slovenia
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I think if you will do full test, do it with lights on, if worried still, take one turn off, but I think if you have another amp, voltage won't be that high to kill chip... Up to +/-70V you can go: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.
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Old 10th January 2008, 05:27 PM   #74
djQUAN is offline djQUAN  Philippines
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I have two other amps one for the front speakers and another for the rears. so that might take care of the voltage.

only soldering the fets to the amp8 board and wiring them together is all that's left and then testing if it will run.


I was thinking of first testing it to its limits (input voltage only. I don't have a high current 12V supply) at the bench first.

run it up to max till the SMPS shuts down and see how it deals with restarting after a fault then install in car for power testing. hopefully I don't let the magic smoke out.
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Old 10th January 2008, 05:34 PM   #75
luka is offline luka  Slovenia
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Yes test it to its limits first, amp should mute if you have overvoltage set lower then 68v. I think everything will go as planed...

Please make video when you will test it in car, allway like to see DIY stuff brake things like speakers
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Old 10th January 2008, 07:49 PM   #76
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Hey, I don't mean to take this offtopic, but i also want to build an amp8 but for home use.

a 1000va toroid will be extremely heavy, so how hard would it be to make a SPMS like you have done, but that runs from 240v instead of 12v?

Would it simply be a case of having 20 times less windings on one of the toroids?
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Old 10th January 2008, 08:02 PM   #77
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nope. you will have to redesign the whole circuit.

I have built several SMPS's for car use but haven't had the guts to make an offline SMPS yet.

the risk of burning your house down or killing someone is possible when you don't have enough experience with those things.
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Old 10th January 2008, 09:58 PM   #78
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Quote:
Originally posted by djQUAN
nope. you will have to redesign the whole circuit.

I have built several SMPS's for car use but haven't had the guts to make an offline SMPS yet.

the risk of burning your house down or killing someone is possible when you don't have enough experience with those things.
Gotcha, I guess there's not really as much risk when running things from 12v as there is from 240v.

I don't really know much at all about doing your own SMPS, so I may just go with a toroid for now, and build or buy an SMPS later on.

Also, have you thought about putting a few high current schottkey diodes on yer PSU rails? each one should knock 0.5v or 0.7v off the rails which would result in less chance of ever giveing the AMP8 70+v. Just have say 5 in series for 2.5v drop.

EDIT: Just one more quick question, would it be very difficult to build a 25v psu that runs from 12v car battery? I would need around 10a of output current, so run an amp9 at full power in my car... If you know of any good links or info on where to start that would be great. I don't mind winding own toroids as I have loads and loads of solid copper wire.
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Old 11th January 2008, 06:00 AM   #79
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I have thought about the diode trick but there is not much room to work with.

a small SMPS for amp9 is easy. there is a schematic in the power supply design forum somewhere. try to PM 'N-Channel' as he has made several of those converters already.
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Old 11th January 2008, 08:46 AM   #80
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it's playing music!!!!!

here's how my workshop floor looks like right now.
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how the fets are mounted
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it's alive!!!!
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some waveforms:
gate drive 5v/div
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primary waveforms:
took that with the ground lead connected to chassis. don't know if that was causing the spikes. the heatsink stays cool. 10v/div
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after the half bridge:
20v/div
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the thing on the bench:
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and then it blew!!! It was playing then I heard a very loud pop then the safety bulb in series with the supply glowed.

Click the image to open in full size.

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a metal flake must have gotten under the kapton tape.


the old chassis and boards:
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