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more CM4 fun stuff. -3d laser printing for temp control.

This was the result of about 12 months work to get the 3D printed box optimised and get CPU temps under control.


The CM4 was installed on the best quality Swiss made board.
(we had one fail for no good reason - losing all HDMI output)

I already expressed doubts when purchased as to how it could be possible to keep the CPU temps down without forced (noisy) cooling fans.
Using it for High end audio makes it that a no-no.

Using a sierra modem for 4G/LTE as well as wifi on the rear bound m.2 made the entire unit prone to RFI which was audible.

I lined this case with some aluminium foil, bought a UFL pigtail for the wifi and moved it outboard on SME connectors.

The Sierra M.2 modem also produced strong rfi so I had to buy the delicate little MHF/IPEX4 pigtails which turn out to be a "pig" to install...some are better quality than others - so wrecked a few of those.
The 2 x 4g antenna are also moved outside the main Tofu board area.

The box was originally a Geerling 3d-laser idea, strongly modified to make it bigger and much better.

The original smaller heatsink couldn't cope particularly in hot summer weather +40C. When running HD video and audio out temps without a fan would allow about 10 - 15 mins before overheating.

I got the proper heatsink which now is so big lots more things had to moved around and the vents redesigned to clear the gpio extension riser...

It was absolutely clear the 12V fan - run on 5V to decrease speed/noise was doing not a lot to keep heat in control once ambient temps rose, and that was partially caused by the GPIO riser getting in the way.

I could keep temps down to below 42-48C flat out, but this was still not good enough, and it had to be compact.

After the installation of the better heatsink - (this company have excellent service) temps dropped again to in the high 30s under load but with still peaks around 40C


here it is installed with the latest addition

- explanation to follow:-
here is the DAC board installed directly on top of the CPU.

The idea is to make the smallest most compact best performance DAC (Ian Canada's dual sabre) possible.

As you see the DAC compromises most efforts to keep things cool.

I modelled a sort of funnel from the fan using duct tape, old baco alloy foil and a alloy plate to stiffen in order to come up with a prototype we could copy, then took it down to my friends in Lyon to print it.

The result was a really fiddly thing for them for which they have to make a support/former and which makes putting the nuts and bolts into the case quite a struggle.

Re-placing the outlet vents and optimising the airstream - lower noise and these wonderful results.

A CPU temperature as I write this post of 29-31C

Original ideas were posted here but suffered the usual nonsense and dissing.* (mostly from a loud mouthed cret..n who qualified himself with more than 9000 posts to commentate on everybody and anything he has absolutely no knowledge about!)


The audio output of the DAC is fed into a pair of rather rare sowter transformers (ex-studio console).

All that had to be mounted on top of an extra alloy slab connnected to the I/V board then grounded to remove all hum and parasitic noises.

This is by far and away the most compact "REAL DEAL" that could ever be done, and the resulting audio is superb.
I think better than the recommended Lundahl LL1544A,

(and I venture to say likely far better FR than the way overpriced/overlarge Bisikek ones)

Edits: 02/04/24 02/04/24

This post is made possible by the generous support of people like you and our sponsors:
  Atma-Sphere Music Systems, Inc.  

Topic - more CM4 fun stuff. -3d laser printing for temp control. - ivan_terrible 02:53:30 02/04/24 (0)


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