Can I use MANY MANY low power devices for 1 HIGH power amp? - Page 2 - diyAudio
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Old 30th January 2003, 01:13 AM   #11
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When a given generation of engineers that relied on a certain class of active device because there were none better, are all finally dead and gone, then those active devices have a big conference and decide to improve their sound because now people are only going to be playing with them and having fun. When people treat active devices seriously and lives etc. depend on them, active devices recognise this and act very proper and conservatively. So they sound very ordinary. But they like having fun and when they know their serious days are over they let their hair down and change their personality and help us to enjoy ourselves hifi-wise. Maybe germanium transistors have come of age? Same goes for old cars (excluding VW Beetles of course).
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Old 30th January 2003, 01:27 AM   #12
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riiiigggghhhhttt... anyway, I think I will NOT sure many many devices, too much trouble.. I am thinking of making either the Silicon Chip Ultra Low distortion 2 X 100watt stereo amp (which gives 100watts into 8ohms) or the 200watt mosfet amplifier module (which gives 150watts into 8 ohms) The 100watt one is in the Novermber 2001 Silicon Chip magazine (if you have it Circlotron) and the 150watt one is in the August 2001 mag. Both KITS are sold by Altronics. I am able to get the PCB design for the 100watt one, but not for the 150watt..

Here are the specs on both amps, are these any good?

Ultra Low Distortion 100W Stereo Amplifier Kit
Specifications:
Output power: 100W @ 8 Ohm
Signal to noise ratio: 109dB A weighted
Distortion: 0.002%
Frequency range: 20Hz-20KHz ±0.5dB
Dimensions: 422W x 400D x 88H
Weight: 12kg

200W MOSFET Amplifier Module
Specifications
Dimensions 300W x 82H x 225D
Output power 140W RMS into 8 Ohms, 200W RMS into 4 Ohms
Signal to noise more than 100dB below rated output
Distortion 0.007% @ 200W

So, which one should I waste my money on? If I was to design my own PCB for the 200watt MOSFET amp, chances are the design wouldn't be as good, and would result in noise... But I do have a PCB layout for it.... so I could do it just the same..
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Old 30th January 2003, 09:24 AM   #13
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Fine examples of designing for low spec.

Impressive though the specs are, these amps sound just like any other mass produced or kit power amp of the eighties. I've heard them all, and they are unsatisfying.......

Cheers,

Hugh
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Old 30th January 2003, 10:16 AM   #14
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Are you saying that the 200watt MOSFET amp will sound no better than a pair of bridged LM3886 ICs?? HERE IS THE SCHEMATIC!!!
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Old 30th January 2003, 10:42 AM   #15
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Given the transistor choices I would build a Hadley with doubled 2N3055 for the outputs.

http://home.kimo.com.tw/skychutw/Circuits/Hadley622.pdf
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Old 30th January 2003, 10:45 AM   #16
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LOL.. I have given up on the MANY MANY transistors idea, decided it was just as expensive, and impracticle.... I hate having to mount just one device... I say NO THANX to 20... lol
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Old 30th January 2003, 10:47 AM   #17
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I think Dr Meier's idea is cool but otherwise I can't see any reason to be thinking of paralleling amps like he does. Save little money first and buy appropriate transistors.
Yes, it´s a crazy idea but he´s gone for it!
He must have a good deal with National Semiconductor.
I actually don´t have the knowledge to judge that but i doubt it´s an effective solution to get a good sounding amplifier.
And the trouble you probably end up in combining all those high-speed devices...
I just can´t believe he managed to make the PCB design work without oscillations.
At least he saved the money for the heatsinks

Jens
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Old 30th January 2003, 11:10 AM   #18
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Okay, I would LIKE to make the 200watt MOSFET amp... tell me why I shouldn't, and give me other options.... Okay, I think I found a big enough reason why not to make it.. THE COST OF THE MOSFETS!!!! Well, I can probably get them cheaper (haven't looked) BUT $15 EACH!!! thats $120 JUST for MOSFETS in a stereo amp..... PLUS about $150 for the 2 transformers, $40 for the heatsinks.... THATS $310!!!! AND I STILL NEED THE AMPLIFIERS FOR THE TWEETERS!!!!! bahh, I think I will finish my speakers, then put them in storage.. WHY ARE THINGS SO EXPENSIVE!!!! Perhaps I should just bridge LM3886s or somthing similar.. BUT ITS NOT THE SAME!!!
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Old 30th January 2003, 06:09 PM   #19
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what about using MANY MANY high power devices for 1 low power amp?
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Old 30th January 2003, 06:18 PM   #20
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Quote:
Originally posted by SkinnyBoy
Okay, I would LIKE to make the 200watt MOSFET amp... tell me why I shouldn't, and give me other options.... Okay, I think I found a big enough reason why not to make it.. THE COST OF THE MOSFETS!!!! Well, I can probably get them cheaper (haven't looked) BUT $15 EACH!!! thats $120 JUST for MOSFETS in a stereo amp..... PLUS about $150 for the 2 transformers, $40 for the heatsinks.... THATS $310!!!! AND I STILL NEED THE AMPLIFIERS FOR THE TWEETERS!!!!! bahh, I think I will finish my speakers, then put them in storage.. WHY ARE THINGS SO EXPENSIVE!!!! Perhaps I should just bridge LM3886s or somthing similar.. BUT ITS NOT THE SAME!!!
Cool now! How many pairs do you really need and what type?

You need one or two pairs per channel and 15$ each seems much. You need 180-200 Volts, 10-15 A, 100-150 W, Rdson unimportant. If you lower your demand to 100 W = -3 dB! Think about that!
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