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Old 10th January 2008, 10:31 AM   #1
dell is offline dell  Philippines
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Thumbs up 1400w amp in 4 ohms

Good day to all! Any body here has built this amp from ESP Project 117? I am interested with this amp. I want to know if there are design stuff to be added or to be modified. Please share some experiences during building this amp. Please refer to attached file. Thank you.
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Old 10th January 2008, 03:42 PM   #2
wg_ski is offline wg_ski  United States
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I see somebody moved this one while I was working on it....

That amp is intentionally left incomplete so incompetent amp builders wouldn't kill themselves or start fires trying to build it. With a few minor modifications it can be made to work. Q3 and Q6 require base stoppers, and C3a needs to connect from - input to the collector of Q6 (not output node, there is too much phase shift in the output stage). C4 needs to be set by experiment. A few other things are needed to make it sound as good as it can. If you don't know *why*, or don't know what I'm talking about then you don't really need to be working on anything this big yet.

A more complete working amp can be found here


but just having a schematic doesn't guarantee working results or safety. In that same thread, Djk publishes a much simpler design close to the same power level.
Old 11th January 2008, 08:37 AM   #3
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Is This Amplifier Worthwhile Building
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Old 11th January 2008, 09:08 AM   #4
dell is offline dell  Philippines
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Default djk posted amp

The amp posted by djk has no power supply circuit. Would it be the same with the qsc supply- no large value filter capacitor? Can you give me some insights why those amp doesn't need a filter cap? What about voltage regulations? the ripples in the supply isn't a problem?
Old 11th January 2008, 02:27 PM   #5
wg_ski is offline wg_ski  United States
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djk's circuit *is* the QSC amp - with some minor revisions. They do require big filter caps - the series connected pair is BOTH the filter and output coupling caps. They serve both functions simultaneously. At small signal, they're inside the feedback loop and don't affect bass response, but the bigger they are the better power you'll get at clip at 20 Hz.

The one catch with this circuit is that the power supply is FLOATING. You need one for each channel, although commonly it's a separate winding on the same transformer core.
Old 11th January 2008, 05:44 PM   #6
jaycee is offline jaycee  United Kingdom
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If you really, really need this sort of output power, buy a Class D based power amplifier used for PA/stage work. It will be cheaper to buy than build, and to build any Class AB amp for this power level will be dangerous, and generate more heat than you could deal with.

Same comment as on this thread, really
Old 11th January 2008, 07:01 PM   #7
wg_ski is offline wg_ski  United States
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A decent class H PA amplifier still costs around $1000. Class D more than that. And if you want to run 2 ohms in 95 degree weather in full sun you need to buy two. If you're actually up to the challenge of working with dangerous voltages and curents, and are any good at scavenging expensive hardware you *can* build one built like the proverbial brick s-- house for less. Any amp is more expensive to build if you go pay full distributor price for even half the parts. Anyone seriously considering building a multi-kW amp probably already has the transformer(s), heat sinks and caps or can get them cheap. If not, sticker shock would have already discouraged the idea.
Old 13th January 2008, 01:25 AM   #8
dell is offline dell  Philippines
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Default amp

Thank you all! The feeling of being successful in a project is the one i want to achieved... No proplem with heat sinks, I can buy transformer and large heat sinks scrap from a CO2 welding machines here in our shipyard. And for the filter caps many stores here in cebu sell such large value. But my problem is the reliability of the parts here. Many of them are sub standards. You can find it by just looking at it's physical appearance specially the high power bipolar transistors. I dont think where this parts came from, maybe from china? Is there a store in the net that can deliver such items (which is guaranteed original) up to here in cebu?
Old 13th January 2008, 08:05 AM   #9
Eva is offline Eva  Spain
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Avoid Chinese fake transistors, they are not up to the job. Search the forum for threads on counterfeit/fake transistors (google will provide some useful pages too).
I use to feel like the small child in The Emperor's New Clothes tale
Old 13th January 2008, 12:54 PM   #10
djk is offline djk
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If you actually want a working amp, don't even think about the ESP design.

What I would so would be to build the Super Leach and go from two output sets per side to six output sets per side. With the proper transistors and a couple of other minor changes it will run from 135V.

The difference of why this amp will work, and the ESP will not work is the series connected output stage.

Candidates for the Darwin Award should not read this author.

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