Ultimate case design - best materials?

Besides being free from vibration and providing shielding, I don't think the case should impact the sound quality of the circuit inside. Cold-rolled steel is an excellent metal for shielding but harder to work than aluminum. Copper tape lining the inside can also provide shielding.

Locating the power supply away from the small signal electronics is a good idea.

If we're talking ultimate here... I guess you could line the inside with mu-metal too.

yes, copper foil really isnt going to shield much of anything that you would be trying to shield from in a case like interference from the transformers or whatever. copper foil is only effective for shielding from a fairly specific band of low level interference. you need much more dense materials to provide that sort of damping. mumetal would do better.

Stop drinking the kool-aid, maybe?

What you make the case of has less effect on "sound quality" than what you use to insulate the wiring inside the case, which has less effect on "sound quality" than what the wires are made of, which has less effect on "sound quality" than what the solder is made of, which has less effect on "sound quality" than what famous audio celebrity designed your circuit, which has less effect on "sound quality" than how "burned in" your opamps are, which has less effect on "sound quality" than having followed good assembly and construction standards, which has less effect on "sound quality" than having a circuit that's well laid-out, which has less effect on "sound quality" than using a well-designed circuit...

I could go on, but I think you get the idea.

Not to be especially antagonistic, but I'm willing to bet your DAC will perform no differently - audibly, measurably, as scried in steaming fresh chicken entrails by a Voudoun priestess - in a case made from 2mm aluminum, or in a Pringles can... and the Pringles can will be a lot easier to work with.

Now that I've expressed my personal opinion, let's cut to the audiophile-approved answer: For the absolute best sound quality possible, use 32mm thick oxygen-free cryogenically-treated magnalium, with a 50um titanium-oxide coating, lined with 3.8mm of mu-metal, a 10mm layer of lead, and an oxygen-free copper faraday cage, each successive layer isolated by alternating layers at least 3mm thick of solid teflon and hard vacuum, isolated by sulfur-free natural latex rubber shockmounts/insulators. To reduce standing waves, all holes in the panels should be chamfered at between 30 and 32 degrees, and everything should be held in place with stainless steel M10 bolts no more than 1-3/4" in length. The case should be supported with spikes investment cast of tarnish-resistant palladium sterling silver, resting on natural ivory supports hand-machined by Tibetian monks. Also, you should put the power supply in a separate, identical enclosure, and keep the two enclosures at least 1/4KM apart, oriented at exactly 90-degree angles.

Good luck. :P

well damping isnt insignificant, but i'm mostly in agreement. I only mentioned the mumetal as shielding, as copper foil would be a total waste of time if thats your aim IMO. at least mumetal would actualy do the job (if it needs doing) and foil will not

I am so, so sorry that is too long to go in a signture block.

I've toyed with the idea of building an enclosure of granite, or other similarly robust rock. If you pick up the right inclusions in the rock, you even get shielding for free. Vibration damping? Check. Pretty? Check. Durable? Check. Fireproof? was born of fire.

Now, it's a real pain to work, and stupidly heavy, but you said ultimate right?

for heavy bass, Osmium is the ultimate. Don't rub the oxidation off the case with exposed skin though.
ultimate treble extension is Lithium. You have to listen in an inert environment though. Lithium case in a helium atmosphere can get sibiliant.
Smoothest liquid sound comes from a Mercury case but you have to listen below -40 F. Watch the class A bias.

I've had the same idea. There's a granite showroom right by my house, I'm sure that they have plenty of scraps.

I think your conclusions are reasonable apart from the lump of steel in the base. Fine for adding some mass if you want to, but some would suggest keeping away from ferrous materials is a good idea on grounds of SQ. Indeed if you are unlucky you might find that the steel plate spreads hum from your mains transformer to the rest of the circuitry.

From what little I know screening is a black art. You might wish to keep stuff away (such as the magnetic transformer field and the digital RF hash) from the analogue sections as well as keep this stuff out of other audio equipment or even local radio sets. From my radio amateur days I recall there there are 2 types of interference; electromagnetic and electrostatic, and they both require different ways of shielding. One to enclose and one to deflect. The low frequency electromagnetic stuff is typically generated by mains transformers and can indeed be effectively dealt with by putting the transformer in a mumetal box or can. The idea being that the magnetic field emitted by the transformer circulates within the mumetal and does not escape into the outside world. It works the other way round to keep noise out of microphone transformers and other sensitive circuitry. Any ferrous metal will also do this, but to a lesser extent. High frequency noise (in the 10,000’s of Hz) can be effectively shielded / deflected by copper (or any conductive) sheet or foil that completely encloses circuitry and is electrically connected to earth.

Mumetal though (which I also think was once known as ‘Radiometal’) is both expensive and has to be heat treated after fabrication to get the full effect of it properties. One would normally go to a specialist fabricator with heat treatment furnaces to get screens made and they would supply the metal as part of the deal. It is not normally sold on its own as it is not much better than mild steel without heat treatment. But because of the cost of fabrication etc mumetal these days is only found in professional and military electronics. We used to buy foil for prototyping work but it was not that useful. Also once heat treated you need to avoid bashing it as this will destroy its screening properties.

I’m with Nemo de Monet, though I prefer unobtainium to his magnalium.

I think you misunderstood my recommendation regarding copper tape - it's for shielding the inside of the enclosure from RF on the outside of the enclosure, *not* shielding the inside of the enclosure from the transformer that's also inside the enclosure. I don't see how any case design could inherently shield from interior low frequency fields, unless it included something like an sealable chamber made of cold-rolled steel (or mu metal if you want to hurt your wallet).

Just get a transformer that is shielded, you do not need to shield it. And you do not need to shield the rest of the PSU.