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Old 26th January 2004, 01:49 PM   #1
jaybird is offline jaybird  United States
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Question Amp suggestions for @ $400 U.S.

Hello, I was wondering if anyone could recommend the best amp I could build for about $300 u.s.
I would like to have: 250-300 watts in 8ohms to drive my towers. I would spend more if it were truely worth the extra expense.
Any suggestions are welcome.
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Old 26th January 2004, 05:48 PM   #2
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try this sight. Rod is a contributer from time to time and all his designs seem to be well thought out. This is his latest and seems to have help change his mind about MOSFET output stages.

http://www.sound.westhost.com/project101.htm
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Old 27th January 2004, 12:25 PM   #3
jaybird is offline jaybird  United States
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Thanks for the input. Any other suggestions?
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Old 27th January 2004, 02:18 PM   #4
sobazz is offline sobazz  Denmark
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Of course there is the classic Leach ouble Barreled Amplifier. It's capable of delivering 270w into 8ohm.

http://users.ece.gatech.edu/~mleach/superamp/

However, it is a far more difficult amp than Rod Elliot's.
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Old 27th January 2004, 07:59 PM   #5
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Quote:
Originally posted by glowplug
try this sight. Rod is a contributer from time to time and all his designs seem to be well thought out. This is his latest and seems to have help change his mind about MOSFET output stages.

http://www.sound.westhost.com/project101.htm
I can't speak from firsthand experience, but it looks like an overall good design. I do have a few gripes, though. First, you can't get the component values unless you pay the $22USD x2 for the boards plus shipping to wherevever you happen to be. I think this is unusual since all Rod's other designs I've looked at have the component values listed. Obviously, he has a right to make a profit from his design, but not everybody will want to buy the premade boards and ship them halfway around the world.

Also, if you are particularly rough on your amps, this amp design doesn't have any current limiting or short circuit protection (that I can tell), so if you disconnect and reconnect your speakers a lot, you need to be really careful, otherwise your only hope is that your rail fuses blow before your mosfets do. The leach super amp is a bit sturdier, though. It's got a very well-designed output current limiter, that won't bother you under normal operation unless you try to drive a 2-ohm load, and combined with a thermal switch on the heatsink, it's practically indestructable. I don't know how the Rod's mosfet amp compares to it in terms of sound, but it is a decent-sounding amp that is really hard to break.

$300 might be a difficult budget to stay within at that power level, though. You will likely need a transformer that costs more than $100 to power both chanels, some very large heatsinks, and a large chassis to put it in. Those things alone could cost $250+, and then the power supply filtering caps will also cost a fortune unless you can find them surplus.
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Old 27th January 2004, 08:44 PM   #6
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I slightly altered one of rod's designs a while back (the P3a, which in initial configuration was good for almost 100W into 8 ohms) so that it could be run with higher line voltages and have a greatly improved output curent capability, what I ended up with was still fairly close to the original, but with (in theory, I have yet to receive any transformers of build up the boards for the project, but hopefuly that should happen some time soon) an output curent capability of about 8A, and a circuit that should be safe up to 50 or 60 volt rails (which is at least 130W into 8 ohms, posibly more if you know that your speaker load doesn't drop too low to execed the safe output current level). I posted a thread about it here, and if you go towards the later pages you should be able to find the final design I settled on, along with component values and a PCB layout (which I will hopefuly be getting made up properly soon, as long as it works ok when I prototype the boards). Let me know if you want the eagle files, or might be interested in any spare boards in the near future.

Andrew.
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Old 27th January 2004, 08:54 PM   #7
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ATI has amp modules, fully populated and ready to power up, for sale. I think someone here quoted them to $200 list a piece.

That would be, in my view, pretty good value for 200w/ch amp.
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Old 27th January 2004, 09:38 PM   #8
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A dollar a watt seems a little hopefull. 2-3 dollars a watt seems more reasonable. I spent a $100 on a pair of transformers for my 55W amp.

Seal Electronics has some higher output kits available but like previous posts, you need to factor in the cost of transformers, heatsinks, and enclosure which together can amount to $200.

I'd love to check out Rod's P101 but I already have more amps than speakers. I have little interest in PCB design and don't mind paying. I've purchased other PCBs from him so I've actually peeked at the P101 component values.

His site is a great resource.
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Old 27th January 2004, 11:56 PM   #9
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Default try Ampslab

Take a look at Ampslab.

Ampslab

I dont know much about the company, but their kits include what is needed to get started.

Heps
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