making a glass case?

[Armaegis]

So I had this idea of maybe making the case for my next amp transparent to show off the guts inside. A clear plastic or plexiglass would probably be the sensible option, but glass has such a nice shimmer to it... but how difficult is it to work with glass? Some preliminary reading online shows you need diamond bits and such, but for something more complex like those top plates is this perhaps more trouble than its worth?

[Grainger49]

You can get glass cut to order at a glass supply house.  They will finish the edges and cut holes to your specifications.  It might not be cheap to make a glass top plate.

[ssssly]

Glass is very resonant and will hold a static charge. I have never tried it, but I would think that with transformers attached to it that it could end up injecting unwanted noise into the system.

There is some rather inert plexi out there though. And while it doesn't look the same as glass, well polished plexi has its own distinct beauty.

[Jim R.]

Sounds like a cool idea, but I would worry about the lack of a ground plane, and perhaps even more about potential microphonic problems.  Of course it's all just gussing :-).

-- Jim

[Armaegis]

Glass is very resonant and will hold a static charge. I have never tried it, but I would think that with transformers attached to it that it could end up injecting unwanted noise into the system.

There is some rather inert plexi out there though. And while it doesn't look the same as glass, well polished plexi has its own distinct beauty.

Could you tell me which types would be better than others? Just browsing my local hardware store for brands/types...
Plaskolite plastic
Lexan polycarbonate
Optix clear acrylic
Duraplex high impact acrylc
Fabback acrylic sheet mirror

Sounds like a cool idea, but I would worry about the lack of a ground plane, and perhaps even more about potential microphonic problems.  Of course it's all just gussing :-).

-- Jim

Could I make do with some more bus wire/star ground?

[Paul Joppa]

The ground plane provides shielding, which is not exactly the same as grounding. If you need shielding, then without a conductive box or ground plane you'd have to individually shield all the important wires - i.e. use coax for hookup wire, with the shields grounded at the star ground. It's never easy to know which wires are the important ones!

Of course, depending on the amp's gain and the RF signal environment you may not need shielding. But it's hard to know in advance.

[ssssly]

Have used Lexan polycarbonate and a high impact acrylic (don't remember the brand) to make turntable plinths and liked them both about the same. I ended up going with the Lexan one simply because it felt better to me. A bit less brittle and more tactile feeling. They both sounded the same to me though. And neither seemed very prone to static charge build up.

Both were black though, not clear. Don't know if that makes a difference. Have heard claims that it does but never tested it. I chose black simply for the aesthetics.

[RayP]

I've been using polycarbonate for a number of years now and I really like it.

First it's cheap and you can get useful sizes at Home Depot.

Second it's easy to drill and cut. Don't bother with acrylic. Step drills work very well to create holes for sockets.

Third, since it comes with a protective covering on both sides you can mark out where you plan to drill, cut etc.

Fourth, I don't cut myself on sharp edges as much as I do with aluminium.

Fifth, it helps to be able to see through the top plate when you construct things. Of course this would apply to glass or acrylic as well.

Sixth, it's very strong, almost unbreakable.

The downsides are

First, provides no shielding as Paul says.

Second, tends to collect dust quickly.

Third goes either way, you are proud to show off your impeccable wiring or you are ashamed to show off your rats nest.

In your case if you are really determined to use glass, build it first with polycarbonate. If it works out well, then repeat it exactly in glass using your poly as a template.

ray

[VoltSecond]

Ideas:

1. For shielding, make the bottom a metal plate if you can go solid.  This will hide the dust build up under the amp as it ages and it probably can provide enough shielding.  I've put aluminum foil under an ESD mat to make a simple noise shield on my test bench and is better than no shield at all and is all you need for preamps and power amps.  This is similar to just putting an aluminum plate on a wood chassis.  You could slide a few mirrors over the plate for decoration.

2. If you want semi transparent, can you live with painted galvanized hardware cloth (Home Depot) for shielding and the case?  1/4 inch hardware cloth provides shielding if you are in the far field (say > ~1/2 inch or more away from it.)   Bias the hardware cloth at a 45 degree tilt for an interesting look.  No glass cutting required. A CO2 duster can clean it out.  Make a 1/2 wide wooden frame to hide the edges of the hardware cloth.  Use a small metal plate to hold the power cord and switches.

3. You could also go like Tony did at VSAC.  Just elevate the top aluminum plate, add a few lights and put a mirror under it to see the guts through the mirror.

[Paul Joppa]

Just another note. You guys do know that plastic melts more easily than glass or metal, right?  :^)

[RayP]

Yes, plastic melts but so far it hasn't happened. I suspect in my case I make so many mistakes and have so many extra holes that the heat escapes pretty easily. By the way, that's another advantage, you don't see the holes so easily.

From Wikipedia - Polycarbonate has a glass transition temperature of about 150

[Armaegis]

Hmm, how about a conductive glass...
http://www.rhunt.f9.co.uk/Experiments/Conductive_Glass/Conductive_Glass_Page1.htm