[Magsy]

I'm possibly in, depends on the style. I don't much like the one depicted on the site, maybe in black with less holes cut in it...

 

[BrokenEnglish]

europeans might consider those marvelous galaxy cases of audiokit.it... at least... i would do so..

 

[BradJudy]

For reference, here's a pic of a larger (16x8x2) ParMetals series 20 in anodized black (note that the faceplate is a custom FPE one, not the stock one):

It looks pretty nice, but the anodizing doesn't seem that durable. It scratches more easily than other anodized aluminum items I own.

Some venting holes will be required since the MMM puts out some heat.

 

[Nisbeth]

Quote:

Originally Posted by BrokenEnglish europeans might consider those marvelous galaxy cases of audiokit.it... at least... i would do so.. [/IMG]

Those a good cases, but it's quite annoying that there's only two heights 40 and 80 mm. 40 mm is a bit to thin and 80 mm is much more than necessary. If they were to make a 60 mm high version I would have about 10 different projects for them in various sizes

/U.

 

[z2trillion]

I'd definately be interested in at least 3 of the par metals cases. Hopefully, we can all decide on dimensions. I would prefer it to be wider than it is deep, but I guess we'll have to see what other people want.

 

[uzziah]

Quote:

Originally Posted by amb OK, while we're on the subject of enclosures, and since the boards are expected within days now, I think it's fine time to check for interest in a Par Metal 20-series custom-sized case group buy. As I mentioned in a previous post, Par Metal can make any custom size you want, but it's pricey in single quantities. I asked them about a 6" wide x 2" high x 8" deep case, and the quote was something like $70. However, that price drops to the mid-$30 range for a quantity of ten or more, which is quite reasonable. If there is enough interest, and people could agree to a common specification (size, color, finish, etc), then I suggest someone should step up and coordinate this. I am too busy to conduct this myself, so I am asking for a volunteer. Maybe a separate thread for this is appropriate?

so the par-metal idea would be that we would decide on a CUSTOM size case for the m3 and then groupbuy that custom size. yes?

 

[amb]

Quote:

Originally Posted by uzziah so the par-metal idea would be that we would decide on a CUSTOM size case for the m3 and then groupbuy that custom size. yes?

Yes. The idea is to make the price of the custom sized cases reasonable with the group buy. Since only ten is enough to get the price down, I guess it's possible to have a couple of (size/color/finish) combinations if we could get enough quantity together for each one.

By the way, the 2" high case has an available internal height of 1.85" after subtracting the thickness of the top and bottom panels. It will fit a board with the 1.5" heat sinks, but just barely. See diagram:

You'd have to use short (0.125") spacers to mount the board and put an insulating plastic sheet below the board to safeguard the heat sink screws and parts pins from touching the bottom, and that gives only 0.145" clearance above the heatsink to the top cover. Also, the volume/bassboost pots will have their centers below the centerline of the front panel by 0.205". There isn't enough pin length on the Alps blue velvet to raise them to the center. But then my home-built case also has the pots below the centerline and it looks fine...

 

[primer]

0.145" doesn't leave much room for miscalculation.

 

[BradJudy]

As long as it would be a custom size, does increasing the height really add much cost? It seems like another 0.25-0.5 inch would make it easier to work with.

 

[uzziah]

Quote:

Originally Posted by amb Yes. The idea is to make the price of the custom sized cases reasonable with the group buy. Since only ten is enough to get the price down, I guess it's possible to have a couple of (size/color/finish) combinations if we could get enough quantity together for each one. By the way, the 2" high case has an available internal height of 1.85" after subtracting the thickness of the top and bottom panels. It will fit a board with the 1.5" heat sinks, but just barely. See diagram: You'd have to use short (0.125") spacers to mount the board and put an insulating plastic sheet below the board to safeguard the heat sink screws and parts pins from touching the bottom, and that gives only 0.145" clearance above the heatsink to the top cover. Also, the volume/bassboost pots will have their centers below the centerline of the front panel by 0.205". There isn't enough pin length on the Alps blue velvet to raise them to the center. But then my home-built case also has the pots below the centerline and it looks fine...

in my mind, the thermal dynamics of the heatsink being closer to the lid would actually be a good thing. conduct the heat more directly from the hs to the case and thus radiating to outside air. does that makes sense? though i understand the concern for a tight fit, it seems good to me.

 

[morsel]

Or you could use 1" heat sinks, which is OK as long as you don't jack up the bias too high.

 

[amb]

Quote:

Originally Posted by morsel Or you could use 1" heat sinks, which is OK as long as you don't jack up the bias too high.

For performance reasons I would advise against 1" heat sinks unless there is absolutely no alternative. Such a small heat sink would necessitate operating with reduced bias. The MOSFETs will not be operating in its most linear region with too little bias. The global negative feedback will correct this, but it's best to rely on negative feedback to fix things as little as possible.

 

[silvervarg]

Quote:

the heatsink being closer to the lid would actually be a good thing. conduct the heat more directly from the hs to the case and thus radiating to outside air.

The major concern is if heatsinks touch the case (e.g. when case is pressed down). Unless you use insulation the heatsinks are live, so if they touch the case we can have a major shortcircuit.

In general you want to have air slots so air can escape through the chassi, preferable just above the heatsinks. The distance from heatsink to top of case is not very important.

 

[uzziah]

Quote:

Originally Posted by silvervarg The major concern is if heatsinks touch the case (e.g. when case is pressed down). Unless you use insulation the heatsinks are live, so if they touch the case we can have a major shortcircuit. In general you want to have air slots so air can escape through the chassi, preferable just above the heatsinks. The distance from heatsink to top of case is not very important.

good point. thanks for the clarification. i suppose using a plastic lid, whether full, or cut out such as amb's would negate the possibility of short circuit? of course, it would be more $, especially if it's cut, and if it's not, it wouldn't conduct heat well AT ALL, and i think that would be very bad. i like amb's lid, except i'd be concerned with lots of dust getting in over time. no fans, but i'd imagine it could start looking pretty dirty inside. yes? exagerating?

 

[amb]

If the tops of the heat sinks are close to the (metal) top cover, you should use TO-220 heat sink mounting kits for the MOSFETs, that will isolate them.

Yes, a cutout like mine will cause dust accumulation inside. I built the case primarily with "show" in mind, hence the clear acrylic top, but it's not the most practical solution. I cover the amp with a piece of cloth when not in use to keep the dust out.