Effects of metal enclosures on circuits

Richard,

I think you mean "hydrophobic", not "anhydrous".

Anhydrous simply means "contains no water". Hydrophobic means water repellant.

Chris

 

Thanks for the correction.

 

No sweat. Actually, an anhydrous material would probaby have the exact opposite of the effect you are (I think) seeking. Most anhydrous materials are strongly hydrophilic and readily absorb and retain water. I presume it is the reduction in conductivity you allege has an effect on sound quality?

Chris

 

I am just throwing a carrot in front of the donkey.

 

Alternatives to metal casings have been around for a very long time

consider Ceramics & of course Phenolic Resin .. Bakelite


http://www.bakelitmuseum.de/home/home1024e.htm

 

Bakelite is a beautiful material: it can polish up really nicely.

I have an old wireless . . .

 

I have on several occasions when building diy components had pre-amps or phonostage main boards out of their cases, (usually Naim style sleeves). And I've never once found that they were quieter out of the case.

Phonostages in particular seem to benefit from being cased within a good box with a continuous ground, always being quieter, with less noise, both perceived and measured.

I'd assume that the effects on a pre-amp would be orders of magnitude smaller due to the much higher signal levels involved.

I'd be interested to see any data to the contrary from anyone who builds plastic cases. I don't doubt they Dennis and Richard believe it to be better I'd just like some 'proof'.

 

this could also dovetail into all those discussions about magnetics and cd's ...interesting point here as there mostly alumnium foil

oh dear all hose people who said you couldn't demagnetizes a cd as aluminium was not magnetic !

 

Er, even if the cd foil was pure iron, what earthly difference would it make to the ability of the laser to read the pits if the disc was highly magnetised?

Chris

 

It's not, or at least not ferromagnetic. As such you cannot de-magnetise (or even magnetise) it.

Paramagnetism is a different property.

 

You can't resist can you, any opportunity to play games and diss. I produce acrylic cases!

 

How about an agreed compromise? You are both correct. Let's not let this potentially interesting thread descend into the usual stramasch.

How about using the accepted abreviation for the material you use, Richard? PMMA?

Chris

 

I produce acrylic cases - full stop, I am not in the slightest bit interested in joining a dissing match with SQ, as has happened probably a few hundred times in the last four years. You would think he would be bored with it by now. It finished the last thread on this subject in exactlly the same way, and if he carries on with it I am out of here to.

 

I am presuming that with products biased into class A, or better put amps that get very hot (valve amps, mosfet amps etc) then this type of case work is a non-starter?

 

Ok, I did try...

Chris

 

Yes you are right, it will warp.

 

Richard, might I suggest that you give the victim angle a rest and simply accept that you are not going to make people change the way they refer to materials just to fit in with some curious misconception that you hold that people think poorly of 'plastics'.

You seem to be unwilling to move on, or even make the vaguest attempt to actually discuss the pros and cons of your chosen materials selection, I can only assume that you are actually unable to do so due to a lack or materials of electronics knowledge in this area. If the best you can do is state ' it just sounds better' then you really haven't got very much to add, have you?

Your assessment of my motives is about as far from the truth as you could possibly get. I assumed because you had chosen t post in this thread, that perhaps you were willing to enter into a discussion, but it's obvious that you are simply fixated with your persecution complex and unable to move on.

 

So as now it has been officially recognised as a piss-take by Rob any more posts calling my cases plastic that are not removed will mean I am out of the thread.

 

So back to Bottlenecks post.

Acrylic has a surprisingly good heat dissipation ability, which is very usefull as it means heatsinks can be mounted directly to it. This is fine up to about 80c but after that the acrylic starts to become more mobile and expands which gives a ripple effect. This wouldn't be very attractive even on the base plate so class A solid state amps would be pushing it unless a fan is incorporated as well.

With valve amps, well I think no real problem. It is a question of how hot the valve base becomes and how thick the acrylic. Acrylic is now available in 20mm plate thickness and that can dissipate a lot of heat, so a 20mm chassis would be safe (far safer that metal as it is a an insulator up to over 10kv, so no addition insulation would be required for underside wiring. I think it would be a very good material and if someone wants to try it I will put that person on to my supplier to have a plate made. Now hole cutting is a problem and specialised bits are required for acrylic of that thickness or you will constantly be jamming the drill. The supplier is fully CNC equiped so any arangements of holes or slots are cut easily.

I think you should try one Bottleneck, it would make a very attractive solution. The mirror qualities of the acrylic would reflect the valves and their heaters beautifully.

 

It would be an interesting and different aesthetic.

Brian cherry at diyhifisupply (a brand I like) has started manufacturing valve amps in bamboo.

I must dig up his explanation around this unusual choice of case. It may be similar to your own reasons for moving away from metal.

How do you find acrylic strength? I had a gyrodec years ago and I cracked the lid. Is it the same sort of stuff?