Modulus-86 Build

[ineedaname]

So I am working on a pair of full range speakers, and needed an amp to drive them. I seen the Modulus-86 amp that Tom built a while back, and decided to try it out. I ordered 2 boards from him, and all the parts to populate them, and I have to say I am glad I chose these amps.

So now I have the amps built, and they are just sitting on the table out in the open.. So I started working on a case, and that's what this thread will mainly focus on.

I decided to use some plywood from my local hardware store as the case material, using the heatsinks as the sides. I originally planned on building 2 cases, one for the amp, and one for the power supply.. however I have decided to put everything in one case to simplify things.

The front panel uses 12mm plywood, and the rear panel uses 9mm plywood. I am going to try to find a metal panel for the bottom, but I dont have many options around here for that kind of thing. The top will be made using some more 9mm plywood, and the bottom will be too if I cant find a metal panel.

I plan on staining the front panel a redish purplish some kind of color, haven't found something that screams at me just yet. The rst of the amp will probably be painted black. I am also going to try and get the heatsinks anodized and dyed black.

Still working on the internal layout a bit, but I should have that done by the end of the night. My biggest concern I have using the plywood is that noise will be able to enter the amp, so I have to find a way to prevent that.. any idea guys?? Any suggestions for anything else are welcome

 

[tomchr]

Online Metals in Seattle is a good option for the metal bits needed for a chassis. Their shipping rates are very reasonable. An alternative would be to find a scrap metal place. It's more work to get the bits you need and you'll need to do some prep to make it look nice, but I've gone that route as well.

Online Metal Store | Small Quantity Metal Orders | Metal Cutting, Sales & Shipping | Buy Steel, Aluminum, Copper, Brass, Stainless | Metal Product Guides at OnlineMetals.com

~Tom

 

[ineedaname]

Thanks for the link! Its looking like I will have to order a sheet, and that place is cheaper than the one I found. I just need to figure out how to shield the inside of the case from noise now. I have everything else figured out..

 

[ineedaname]

Okay so this is the layout I am planning, I am worried about the transformer being so close to the amps though.. How much is this going to effect performance if its that close?

 

[tomchr]

Another option would be to move the transformer to the rear panel so all the 60 Hz wiring is as short as possible. Then route the input wiring from the rear panel along the heat sinks to the input connector on the PCB (J2).

~Tom

 

[tomchr]

For future posters: Please note that there's a rather lengthy Modulus-86 Build Thread in the ChipAmps forum (Modulus-86 build thread). I monitor that thread on a daily basis.

Tom

 

[AndrewT]

Okay so this is the layout I am planning, I am worried about the transformer being so close to the amps though.. How much is this going to effect performance if its that close?

I don't expect the transformer location to be a problem.
You will need to measure the Hum+Noise at the outputs when you complete your "on the bench" assembly. This will give you a baseline against which to compare the final assembly.
In my final assembly inside a metal enclosure I have never found the final to be quieter than the strung along the bench test assembly.
Often it takes quite a few hours of moving things around and checking that the wiring really is the same as the test version, to bring the noise levels down to acceptable.

You may find that the radiated field from the toroid is uneven and that rotating the toroid around it's mounting bolt can sometimes attenuate the interference. You need to measure to find that improvement.

I often operate my stereo using uncased test bench style assemblies (sometimes for many weeks). I rarely find any interference affecting my music/audio.