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Old 18th October 2006, 02:11 AM   #1
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Default Point to point LM4780?

Hi everyone,

I have a couple of 4780 chips just laying around and plan to build an amp out of them. I am thinking of doing a p2p build since the pins are too close for me to make a pcb and I don't know how to get a pcb for this chip. I'll run them in parallel so one chip per channel.

Has anyone tried a p2p build with this chips? How many amps is the recommended tranny?

I also need to ask this... are they any good/better than the tried and tested 3875?

Many Thanks
JojoD
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Old 18th October 2006, 02:16 AM   #2
Leolabs is offline Leolabs  Malaysia
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http://www.mhennessy2.f9.co.uk/microamp/index.htm
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Old 18th October 2006, 02:20 AM   #3
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LM4780 p2p is pretty simple:

Click the image to open in full size.
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Old 18th October 2006, 02:34 AM   #4
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Leolabs and Peter,

Now that's what I'm talking about!

One thing is certain though... I must never, never, never make a mistake of cutting the wrong pin of the chip.

How's the sound?

Thanks
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Old 18th October 2006, 02:37 AM   #5
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Leolabs,

The project on the link used a 120VA torroid right?
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Old 18th October 2006, 06:20 PM   #6
Minion is offline Minion  Canada
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Default Re: Point to point LM4780?

Quote:
Originally posted by JojoD818
I am thinking of doing a p2p build since the pins are too close for me to make a pcb and I don't know how to get a pcb for this chip.

Why can"t you make a PCB?? The pins are no closer than any other IC, actually they are quite a Bit farter spaced than say a 8 pin DIP and I make PCB"s with 8,14,16 Pin Dip IC"s all the time without any problems at all.....

I just etched a Simple Chip amp PCB for a LM3886 which is just as small or smaller than a LM4780 and there weren"t any problems at all .....

Maybe it is the method you use for makeing PCB"s?? I just use a PCB Drawing Program to design the Circuit Board, I then take a Screen shot of the Design and then Trace it out in MS Paint with Black lines and Dots and then copy it out on Photo paper and then transfer the design to PCB useing an iron and then Etch the PCB in 2 parts Hydrochloric Acid and 1 Part Muriotic acid and in 5 minutes I have a perfect PCB......


If you really want to try point to point then Just use a Piece of Perf Board and do the Point to Point wireing underneath the Perf board......


Cheers
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Old 18th October 2006, 07:56 PM   #7
reever is offline reever  United States
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You need to look at those chips a little closer. The spacing on the 4780 is much tighter than the 3886 or the 3875.....

Also many more pins on the 4780
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Old 18th October 2006, 08:07 PM   #8
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Default Re: Re: Point to point LM4780?

Quote:
Originally posted by Minion


Maybe it is the method you use for makeing PCB"s?? I just use a PCB Drawing Program to design the Circuit Board, I then take a Screen shot of the Design and then Trace it out in MS Paint with Black lines and Dots and then copy it out on Photo paper and then transfer the design to PCB useing an iron and then Etch the PCB in 2 parts Hydrochloric Acid and 1 Part Muriotic acid and in 5 minutes I have a perfect PCB......


If you really want to try point to point then Just use a Piece of Perf Board and do the Point to Point wireing underneath the Perf board......


Cheers
You really should get a freware version of eagle, it is MUCH less hassle than what you describe to print your PCB layout. Secondly...Hydrochloric Acid and Muriatic acid are the exact same thing and will not etch a copper PCB...alone. I think that you meant a 2:1 mixture of Hydrogen Peroxide and muriatic acid (HCl). Just watch the fumes and the heat the reaction produces.

I agree that that the 4780 can easily be done on a DIY PCB (I have done it myself several times). The hardest part of using a PCB for the 4780 is the awful supply routing. I certainly admire the elegant simplicity of Mark Hennessey's and Peter's P2P efforts. If I were to build another one of these amps I wold likely forgoe the PCB and follow Mark's layout.

G.
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Old 19th October 2006, 02:45 AM   #9
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Quote:
Originally posted by JojoD818
Leolabs,

The project on the link used a 120VA torroid right?
For me,at least 250VA is required.
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Old 20th October 2006, 03:27 AM   #10
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Quote:
Originally posted by Leolabs


For me,at least 250VA is required.

Ok, thanks a lot for the advice.
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