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Re: Copper Chassis-induced current?

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Posted by Allan on April 7, 2002 at 03:29:33

In Reply to: Copper Chassis-induced current? posted by John M on April 6, 2002 at 11:17:38:

Copper is good for chassis, Audio Note uses copper as the chassis of cartridge transformers. Cu reduces the inductance of the whole circuit resulting in a smoother and more open HF.
Aluminium is the second best choice, it is also non-paramagnetic and doesn't cause much increase in inductance, it is also easy to handle(e.g. drill holes). If you need stronger chassis, you may choose Al type 7075. In real life, Al is a bit less warm and less musical than red copper (note that brass is not suitable for chassis).
Steel, though claimed not to be magnetic, still has iron atoms mixed with carbon, steel chassis to some extent, will affect HF and resulting in unnatural sound.
The worst of all is iron, Jadis uses iron as the bottom plate of all its poweramps (they use steel as the main chassis, iron as bottom plate), by replacing or removing the bottom plate, you get a much open and natural sound!
The best chassis I have heard, is one made from one single piece of thick copper, unlike most chassis made by folding up thin metal sheets, this one was drilled into different compartments from one piece of 3-inch thick copper, you can even separate different sections of the circuit into different compartments to reduce interference.
To get over the top, I am thinking of adding a layer of lead into the above mentioned chassis, this may further improve shielding and may help to absorb resonance by sticking two metals with different resonant frequencies together, just like what Symposium equipment platform is doing (they use materials with different densities and resonant frequencies to absorb unwanted resonance). I have not tried this yet.

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