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Old 1st November 2008, 08:56 PM   #1
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Default simple and interesting.possible ????

http://www.electronics-lab.com/proje...053/index.html
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Old 1st November 2008, 09:28 PM   #2
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Default Re: simple and interesting.possible ????

Quote:
Originally posted by sakis
http://www.electronics-lab.com/proje...053/index.html
Impossible physically:

Quote:
POWER :
Maximum Output power @ 8ohms : 300watt
Absolute max power supply voltage :38V to 40V
Recommended power supply voltage :30V to 35V
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Old 1st November 2008, 09:28 PM   #3
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400uF in series with the loudspeaker????
That's going to have TERRIBLE bass performance.

I dunno why the cap is there: besides that part, the circuit is cloned 100% from National's application note.

And it's not going to give 300W/Ch on a 30/0/30 transformer - more like 120-150W/ch.
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Old 2nd November 2008, 12:22 AM   #4
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30-0-30 will give something like 70W into 8 ohms

That circuit has a lot of problems... Looks like the designer had no idea what (s)he was doing.

2N3055 for vbe multiplier??? That's insane!
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Old 2nd November 2008, 08:16 AM   #5
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Default ok ok

my point of view also ....

i think that its a joke .... but let us for a minute try to see some other prospect ....

lets suppose that we increase rails ....how much will be possible ....

and then add a proper vbe multiplier ( complete circuit )

and then borrow the qsc idea ( all transitors mounted to ground and speaker lead comes from CT and psu caps and so on and on

are we getting somewhere ????
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Old 2nd November 2008, 08:42 AM   #6
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Default I was playing with those chips those days


You can see into Youtube many things published showing strange behavior.... noises.... off set fluctuations....movies showing this are there.

They are very sensitive, also unstable and hard to built without face unstabilities... board is critical, distances must be very small...parts position critical too.

They sound good... depending the audio source, the music style and speaker they sound very good but not safe, not reliable, not stable in my point of view.

So..the better could be the circuit surrounding them..knowing those LM4702 represents two LM4701 inside same case, they are not something safe to be used.

The output condenser is small and the power amplifier biasing is not very good.... they are not kidding, just they are trying to offer something plays loud...very loud!....maybe audiophile quality is not the main focus...main target.

About LM4701 (same circuit inside LM4702) here into youtube:

http://www.youtube.com/watch?v=F5tr4gHsNkU

regards,

Carlos
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Old 2nd November 2008, 10:46 AM   #7
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I think it's definitely someone who doesnt know wtf they are doing! That chip has been tried by various people in the Chip Amp forum and they've had great success with it, though.
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Old 3rd November 2008, 08:08 AM   #8
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Default Can you be more precise about the one does not know


what was doing.

Mr. Jaycee.

As you have perceived this...why don't you do it better?.... say... in the case of bad made design, do it better and offer to us the corrections needed.

If not well tested, them produce better testing to us...be positive, do something can be usefull.... criticisms may be interesting, but has lack of result...do not help us ..will not make the designer better or the evaluator better.

Teach us how to do it better...or to evaluate it better... help us to leave the ignorance behind... give us a chance to evolute!

As you may know things we do not know... why not to share with us?

regards,

Carlos
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Old 3rd November 2008, 08:51 AM   #9
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Default THANKS

UNCLE "VALVOULA" CHARLY .....

i licked very much this xpression ha ha ha

yes this is the idea about

as many times said by me and probably others this might be a simple cheap approach with qualities similar expected ....

mercedes is a car but also hyundai is a car ....

may be after all should exist some permenet thread about simple to make cheap with related quality audio

since quality amps exist more than many in this forum


i recall in one post was mentioned one amp that psu and circuit was calculated in this way so in case of output shortcircuit not enough current was ther to cause outs to short ......very weird approach ....but yet was done by a relativelly good designer
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Old 3rd November 2008, 08:20 PM   #10
jaycee is offline jaycee  United Kingdom
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destroyer x, i did not mean any design with this chip that you have done, i meant the design of whoever did the electronics-lab.com thing - sorry for the confusion

I've read and seen the problems you had with the chip. If you don't mind me asking, what transistors did you use at the output? I'm just curious now as I did think about building an amp based around one, but had difficulty sourcing them and also didnt like the idea of not being able to replace them if/when it blew up in 5 years time or so. Instead I'll probably make something not to dissimilar from your own DX Precision amp
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