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Old 4th May 2012, 06:33 PM   #41
AndrewT is offline AndrewT  Scotland
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Keep the Safety Earth (the PE connection to Chassis) separate from the MAG.
They do completely different jobs and are not required to be coincident.
There may be a small advantage to keeping well spaced apart.

If you decide to add a Disconnecting Network (the inverse parallel Power diode link from MAG to Chassis) then they MUST be separate.
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Old 4th May 2012, 06:39 PM   #42
redjr is offline redjr  United States
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I understand the safety issue of the PE wire getting 'accidentally' disconnected. However, what are the odds and real chance of that ever happening in a typical home audio environment? I mean really. At some point, the cover will go on and it will sit on my cabinet for years to come in a stress-free place where nothing is going to shake or work free.

Don't get me wrong. I'm not trying to minimize the importance of the safety element of DIYing. But at some point we can overkill our projects.

In retrospect, I should have secured that wire with it's own nut. That would have made it doubly secure and prevented it from being accidentally removed. However, I did heed Andrews advice and used a much shorter lead and secured it to the back panel. But now I don't have much of a star grounding strategy anymore and the amp is super quiet.
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Old 4th May 2012, 06:48 PM   #43
AndrewT is offline AndrewT  Scotland
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Your MAG looks very "star like" !

The Safety Earth has nothing to do with the Audio.
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Old 4th May 2012, 08:43 PM   #44
redjr is offline redjr  United States
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Quote:
Originally Posted by AndrewT View Post
Your MAG looks very "star like" !
Not now it doesn't. That was an earlier image but since then some needed mods were in order in reduce some hum I was experiencing. A couple of those green wires have been removed. As I mentioned earlier, based on your observation, I moved the PE wire to the rear panel. The amp seems to be very, very quiet now. It was a combination of other input wiring that I changed and the grounding rework that led to the improvements in hum reduction.
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Old 5th June 2012, 12:47 AM   #45
FrankW is offline FrankW  United States
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I'm about ready to power up my LM4702 board and would rather do it without connecting the board outputs to my output transistors first. If I have a workmanship error, I'd rather not smoke my FETs. Does anyone know if the LM4702 is OK with power applied but no load ?

Thanks!
Frank
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Old 5th June 2012, 12:20 PM   #46
macboy is offline macboy  Canada
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Quote:
Originally Posted by FrankW View Post
I'm about ready to power up my LM4702 board and would rather do it without connecting the board outputs to my output transistors first. If I have a workmanship error, I'd rather not smoke my FETs. Does anyone know if the LM4702 is OK with power applied but no load ?

Thanks!
Frank
Take a look at the Test Circuit on page 10 of the datasheet and see if that answers your question.
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Old 5th June 2012, 03:07 PM   #47
FrankW is offline FrankW  United States
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Hi, Macboy,

Thanks - I must have looked at that half a dozen times before and not realized the outputs are tied together for bring-up. Also, thanks for the instant advice!

Cheers,
Frank
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Old 2nd October 2012, 01:55 PM   #48
layws is offline layws  Taiwan
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My DIY project use LM4702 and seaken STD03N and STD03P
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Old 11th October 2012, 09:45 AM   #49
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I want to make an amplifier of 240w rms by using LM4702 (+/-75v supply) for public address purpose. Kindly help me
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Old 11th October 2012, 11:07 AM   #50
AndrewT is offline AndrewT  Scotland
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look at the datasheet and application notes from National.
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