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Old 23rd July 2006, 03:51 AM   #1
Leolabs is offline Leolabs  Malaysia
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Question shield or not shield???

I have seen lots of Gainclone,with metal,wooden,plastic.........boxes.So does a Gainclone actually need shielding or not???
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Old 23rd July 2006, 04:40 AM   #2
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mine was in a plastic box, and a radio sounded on my speakers quite loud. i had to shield the box with some metal sheets to solve this problem. use a metal box.
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Old 23rd July 2006, 06:30 AM   #3
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it depends where you live as well, i had an unsheileded that sounded great but occasionally taxis are near the funeral home that is close by. when they are there it got some loud interferance.

when i used a metal box i never hear it.
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Old 24th July 2006, 09:25 AM   #4
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What's "Gainclone"?Thanks for any help!
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Old 24th July 2006, 09:37 AM   #5
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Heres an idea and one I have actually implemented, lots of metal boxes look pretty horrible and clearly a nice timber job can be much nicer.
So..
Build a box around your boards/p2p circuit using copper PCB board and then run a ground from the enclosure to the star earth point on the amp. This will kill interference issues and will also help to make the amp more unconditionally stable if you want to use lower gain designs etc.

Of course you must use good quality sheilded cables as well.

It will also help stop interference from the power cables within the case, though this would no doubt be very subtle. Overall although a lot of gainclones seem to work well as far as their owners are concerned but my experience is that attention to lots of little details including really good shielding makes for a much better sound and less troubles long term.

At the end of the day you could then use any outer box type you want and the PCD board solders together pretty easily and is quite cheap for the amount you will need.
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Old 26th July 2006, 04:03 PM   #6
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I built power supply and amp all in one box. I planned on shielding the amp from the supply, but just out of curiousity, I tested with and without, and there was definitely noise coming from my supply. So if you have the supply near the amp, definitely shield that.

I am about a 1/4 mile from some AM transmitters. I found that out after building my amp. There is definitely AM noise all over my board. However, with a source connected, speakers connected, and the normal AC and DC grounds handled properly, it doesn't come through when music is playing. It is, however, contributing to noise when no source is connected.

The enclosure is made from some spare MDF I had floating around.

So there is definitely the risk of noise, but even in my case, where I know the noise is there, it is not audibly affecting the music.
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Old 26th July 2006, 05:24 PM   #7
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I played with laminating aluminum to wood for a while. Seems to work well for RF shielding (I too live across from radio towers).

The example above is walnut with aluminum flashing (comes on a long roll from a home center) applied with contact cement. I then cut the wood (and aluminum) to size on the table saw/router/whatever.
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Old 26th July 2006, 10:46 PM   #8
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(So there is definitely the risk of noise, but even in my case, where I know the noise is there, it is not audibly affecting the music.)

I feel that while the noise may not be audible, it will/may be mixing with the content of the music and causing low level degradation of the sound quality, perhaps a grainy presentation to the treble or mushy bass or just a lack of crystal clarity, so in the end it is best to avoid it if possible, it may also make the amp more likely to oscillate under some circumstances.

Of course earthing is critical with many circuits and my experience with clones is that good earthing can make a huge difference to overall sound quality as does proper sheilding.
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Old 27th July 2006, 08:26 AM   #9
juma is offline juma  Serbia
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Quote:
Originally posted by henry zhang
What's "Gainclone"?Thanks for any help!
Gainclone is a DIY copy of Gaincard amplifier. Study these sites:

http://www.geocities.com/rjm003.geo/...io/diy_gc.html
http://www.dogbreath.de/Chipamps/Gai...nCardCopy.html
http://www.pedjarogic.com/gc/index.html
http://myweb.tiscali.co.uk/nuukspot/...loneindex.html

Have fun !
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Old 27th July 2006, 08:57 AM   #10
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Hi

I'm buiding an MFD case for my 7293 right now.

Quote:
lots of metal boxes look pretty horrible and clearly a nice timber job can be much nicer
That were my thoughts too. MDF is easy to handle, an with some experience from loudspeaker prokects, you can get a very nice finish.


I wonder if RF interference cant't be eliminated with a simple high-pass-filter?

Have you tried alumineum foil from the kitchen?
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