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Old 3rd June 2006, 02:25 AM   #41
dfdye is offline dfdye  United States
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One component I forgot to mention: RG should be a low value 1/2W resistor, either 0R or 1R. If you would rather take the signal ground directly to your chassis star ground, you can simply run an additional ground wire from the RG hole closest to the LM4702 chip (which is the signal star ground on the PCB) to your ground. Since the signal ground and power grounds will now be separated, I don't think you should have any problems.

I haven't had any problems using a 1R resistor for RG, but if you experience any hum this would be my first suggestion.

David
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Old 9th June 2006, 02:06 AM   #42
AJT is offline AJT  Philippines
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David,

got my boards today, thanks a lot. do you have chips and parts you can sell me?
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Old 9th June 2006, 06:18 PM   #43
dfdye is offline dfdye  United States
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I'm working on it. I think there might be a group buy on parts in the near future.
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Old 10th June 2006, 03:06 AM   #44
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Got my boards. I'm in on group buy whenever.
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Old 14th June 2006, 03:06 PM   #45
dfdye is offline dfdye  United States
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Brett, and others:

I am putting together a few brief comments and suggestions regarding the board and I should be done sometime this weekend. I'll put in some suggestions as to my favorite component configurations and a simple darlington output stage. Most of what I have been playing with lately has been based off of the new information from the National AN-1490 application note. Most of the suggestions they have in the note are easily implimented in these boards, but a couple of things aren't too obvious, so I want to make sure everything works before I tell others to try things!
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Old 14th June 2006, 07:28 PM   #46
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read the app note, but i do not agree with the groundplane thing, i have built lots of leach super amps with ground plane boards and never had issues with it.
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Old 14th June 2006, 07:47 PM   #47
dfdye is offline dfdye  United States
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My logic on the ground plane was pretty specific: I wanted the signal grounds in a star configuration connected to a power ground plane via a resistor to avoid any hum while keeping the benefits of a ground plane. In my testing I haven't noticed anything goofy in terms of hum or anything. I still haven't done critical tests, but nothing has shown up on the scope.

David
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Old 14th June 2006, 09:08 PM   #48
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Default Star ground

I'm certainly no guru and no next to nothing about electronics, but I have always used a 1ohm and a 100nf cap from signal to power ground and never had any noise problems. I think it's really imortant just to make it that little bit more difficult for any dirty power to go through into any of the audio section.

Brett
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Old 14th June 2006, 09:26 PM   #49
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I don't see power transistors there... Why ? It will cause again neverendig stream of questions, how you can make it ....
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Old 14th June 2006, 09:42 PM   #50
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Default Boards

David

Thanks for that link. It's good for plebs such as myself and interesting reading about grounding issues.

I think the biggets issue for me is also output stage as I'm no wiz. So this will be the scary point.

And also a good idea to have a group buy maybe. As for some of us it may be very difficult to obtain power transistors needed to get this puppy up and running.

And also, thanks for all the work you have put in so far. This project was on the brink of dying until you gave it a new lease of life



Cheers

Brett
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