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.
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.
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.
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.
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.
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.
(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.
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.
henry zhang said:
Gainclone is a DIY copy of Gaincard amplifier. Study these sites:
http://www.geocities.com/rjm003.geo/rjmaudio/diy_gc.html
http://www.dogbreath.de/Chipamps/GainCardCopy/GainCardCopy.html
http://www.pedjarogic.com/gc/index.html
http://myweb.tiscali.co.uk/nuukspot/decdun/gaincloneindex.html
Have fun !
Hi
I'm buiding an MFD case for my 7293 right now.
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?
I'm buiding an MFD case for my 7293 right now.
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?
Aluminium foil will work, better still cut up one of those foil trays used for cooking roasts etc, it will be much more substantial.
No matter what you use, the important thing is to ground the metal liner to your star grounding point on the amp, to do this you will need to attach some thin wire to the metal foil and solder the other end to the grounding point.
You can't of course solder to the aluminium. but if you take a multistrand length of wire you can splay the individual strands out then tape it to the foil, or if the foil is glued to the case just run a nut and bolt through the case with the wire trapped under the head and a flat washer.
MDF is actually pretty good stuff, it can be finished in an amazing variety of ways that can look really neat if done well, in fact if your clever with wood stains and decorative painting techniques and lacquer it can be made to look like some very exotic timbers.
No matter what you use, the important thing is to ground the metal liner to your star grounding point on the amp, to do this you will need to attach some thin wire to the metal foil and solder the other end to the grounding point.
You can't of course solder to the aluminium. but if you take a multistrand length of wire you can splay the individual strands out then tape it to the foil, or if the foil is glued to the case just run a nut and bolt through the case with the wire trapped under the head and a flat washer.
MDF is actually pretty good stuff, it can be finished in an amazing variety of ways that can look really neat if done well, in fact if your clever with wood stains and decorative painting techniques and lacquer it can be made to look like some very exotic timbers.
Bassterror said:
Shielding is always better than filtering. Filtering is a last resort when shielding doesn't work. Once RFI is on your lines, you have a variety of messes to clean up. Keeping it off your lines is the first goal. It's not always possible, so there are a lot of methods for filtering. High pass filters help, particularly in the form of ferrite beads.
I work with RF for a living, so I've spent many hours chasing RF and trying to filter it off different lines... The best result is always to find out where it's getting in and shield it.
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