New LM4702 Build

[redjr]

Hi all -

I'm getting ready to build my first amp build based on the LM4702 chip using pre-assembled modules. At this point I'm not sure of the final design, but the amp may morph into more than just a power amp. I'm thinking of possibly including a pre and DAC modules as well. The whole shebang!

I've started to gather all the parts I need, including a big, hefty toroidal xformer. I'm now starting to look at chassis' and enclosures and hence my question.

The size of the case I'm looking at needs to be about 16 x 12 x 4. I'd like the case to have both top and bottom plates removable for ease of access, drilling and wiring hookup flexibility. I'd also like the bottom plate to be a little thicker than the rest of the enclosure for added sturdiness and strength. At this point I feel I can't be too picky with what I find that comes close, but I suspect aluminum is easier to work with. In the end I do want a case that looks smart, well designed with a bit of eye-candy to boot.

I don't have the equipment to construct my own enclosure so therefore need a third-part solution. Since most of you all are a lot more seasoned with building amps... My question is, where is the best place to start looking for the type of enclosure I'm after? I've seen a few possibilities on the Hammond site and a few on eBay, but still nothing that fits the bill as I envision it.

Can you guys provide some additional links to other sites that offer a variety of chassis' and enclosures for DIY projects. Much thanks.

[redjr]

In helping me decide what exact size chassis I need, I cut a piece of cardboard to use as a template for the bottom plate. The attached picture shows a 16" x 12" (cut to scale) piece with a tentative layout of the modules. There's plenty of room using this size, and extra space for additional modules should I decide to expand this project. A 16" x 16" size would give me plenty of room! Par-Metal does have what appears to be a nice, basic case, with no bling, wood sides, or anything else. ;(

I was going to try and balance the weight of the chassis with the module placement, but it's clear to me the toroid will win the day unless I mount it in the middle. That doesn't make the best and most efficient use of the space though. Balance may not be practically possible.

Any thoughts on special consideration to other layout configurations? Are there any general rules-of-thumb for layout?

[GloBug]

Here are some aluminum chassis. Chinese supplier, no affiliation use at your own risk.
http://www.vt4c.com/shop/program/mai..._id=2&hit_cat=

Keep the power caps close to the main amp board.
You can stick the toroid at the front, this seems odd but it keeps the rest of the wiring to the jacks neat and short.

Have fun, don't be too anal, or you will be like me playing tunes from a breadboard a month from now. Although the cardboard would be easy to drill.

[bcmbob]

redjr - since you live in the U.S. take a run through the electronics sections of your local Salvation Army and Goodwill outlets. Some have found good items to gut and use the chassis without a lot of drilling and bending.

Also, remember most cities have small metal shops that will put a couple 90 degree bends on a small sheet from Home Depot for just a few bucks. Check the Yellow Pages.

[redjr]

Originally Posted by GloBug

Here are some aluminum chassis. Chinese supplier, no affiliation use at your own risk.
Audio Catalog

Keep the power caps close to the main amp board.
You can stick the toroid at the front, this seems odd but it keeps the rest of the wiring to the jacks neat and short.

Have fun, don't be too anal, or you will be like me playing tunes from a breadboard a month from now. Although the cardboard would be easy to drill.

Yeah, I have a tendency to be anal! With this template I wanted to get a sense of the size I need based on my components/modules before I buy. I just like to have a plan - even with my DIY projects. It may take longer, but in the end, I'll have fewer surprises along the way, and the result more predictable. I've kinda zeroed in on a Par-Metal enclosure and now just need to decide on the size. Their cases seem very workable - although somewhat bland and industrial looking. I'd really like some integrated wood side panels. Only thing - which is not a show stopper - is there's no removable bottom plate. In the picture, those caps on the PSU module are 10,000mfd each, so I should have enough filtering.

Hopefully, I won't be using cardboard as my bottom plate!

[redjr]

Originally Posted by bcmbob

redjr - since you live in the U.S. take a run through the electronics sections of your local Salvation Army and Goodwill outlets. Some have found good items to gut and use the chassis without a lot of drilling and bending.

Also, remember most cities have small metal shops that will put a couple 90 degree bends on a small sheet from Home Depot for just a few bucks. Check the Yellow Pages.

I thot about finding an old carcus from an amp or something - even looked through my limited supply, but couldn't find anything suitable. And the thot of going to a metal shop did cross my mind. Great suggestion.

[redjr]

Originally Posted by GloBug

Here are some aluminum chassis. Chinese supplier, no affiliation use at your own risk.
Audio Catalog....

Thanks for the link. I'll take a look and see what they have.

[jimchan]

Hi red

I saw a very nice chassis layout that would work well for Low power DIY amps, but no pictures, sorry...

A thick alu chassis bottom plate that acts as the heat sink, so output devices directly attached. Transformer and pcbs also mounted on bottom plate.

4 sides in wood with nice finish, screwed to the bottom plate, glued at the edges. Wood top, glued to the sides. Servicing from the top.

Cooling was fine, darling ton pair output devices.

[redjr]

jim -

Cool. Sounds nice. I looked at some wood chassis, but they seem to get expensive pretty quick too. As I said in my other post, I'm committed to the Par-Metal enclosure now. I bought an assembled AB module that already has the heat-sink integrated with it and done very nicely and compact too. It would just not be feasible to remove it and put it on another (HS). You can see it from the pictures I posted earlier. I'll post a 'before' picture of the case when it gets here.

Even with the Par-Metal case, I'll either be putting the amp module inside, or make a design decision to hang the HS out the back. The latter will require some significant case mods if I go that route. And I don't have any sheet metal cutting, or bending tool either. I just won't know until the chassis gets here to see what I'm up against. Should be here next week. While I've been waiting I've been in the process of buying the necessary hardware/electronic parts I'll need for this build and others down the road. I'm just getting back into this hobby after about 30 yrs. so I needed to stock up on a few things. When I sit down and ready to put something together, I like to have most of what I need ready to go. Having said that, I'm almost always running to RatShack or HomeDepot for something!

[redjr]

Update. Well, I finally got my enclosure from Par-Metal last week. Took a little prodding with them, but they finally came through. Overall I'm happy, but a little disappointed that the internal front panel and rear deck are different heights! Not by much, but 1/16" makes a big difference when now the heat sink won't fit where I had planned on putting it. Ugh! This is not visually obvious when the case is together, so I plan on living with it. I originally thought I would mount the amp PCB/HS in a vertical orientation over the bottom and top vents for passive cooling. This would have allowed for more room inside too - not that it was needed.

Now I have to go to plan 'B'. I've decided to mount the amp module in a horizontal orientation on stand-offs with the HS facing up. This still leaves plenty of room underneath and above the module for hookup and cooling purposes. This seems like an unusual arrangement, but should work fine. Since heat radiates and rises shouldn't be an issue. While tapping one of the 3mm holes for the stand-offs I broke a tap. Those suckers are hard when you go and try to hand file them down. Now a little drop of oil in the hole before tapping helps.

I've included a few pictures of the bare case, intended module layout and amp module with stand-offs. Nothing has been secured down yet. Still plenty of drilling to do, waiting the arrival of the IEC connector, etc. Stay tuned...