[HAL]

Wanted to try out the Orchard Audio Starkrimson Ultra Class D amp modules and decided to purchase a pair of DIY modules from Leo. 

Decided to try out a different SMPS DC power supply, so purchased a pair of Mean Well SMPS for 36VDC @13.8A PFC version units to stack for the +/-36VDC power supply requirement.  This version SMPS has an aluminum case for cooling and shielding.  Yes, this does mean the total SMPS is capable of 1000W power to the amp modules.  This will probably need a soft start circuit added eventually. 

I am terrible at making chassis for projects, so picked up some 16in pizza boxes for the temporary housing.  Used something similar for the LM3886 Chip Amp project awhile ago, but these are better built boxes.  The SMPS are actually lighter than the toroidal transformers I used for the earlier amp linear power supply. 

Testing the SMPS first to make sure stacking is not a problem with small load resistors before connection to the DIY amp modules. 

[mix4fix]

Hal: You are bad as I was in the 90s. For a while, I ran a car sub in a cardboard box.

PS: I hate when things get throw away when they could be recycled. I could have given you an authentix Tony's box.

[HAL]

mixrfix,
Thanks for the thought.

Was using school pencil boxes when I was a kid for projects.   Even one for a Science Fair project and won a prize!

[mix4fix]

Participation trophy!

But, wouldn't it get hot with the box closed?

[HAL]

Only if I do not put holes in the top.  I just leave it open when running.   

[orchardaudio]

What are your thoughts on these vs the non-ultra ones?

[orchardaudio]

P.S.

Use twisted shielded pair wire between the XLR connector and module input. Like this one...
https://www.digikey.com/en/products/detail/belden-inc/9451-008500/7042018

[HAL]

Leo,
Once they are up and running will let you know.

These are still in build as I need a few more parts for testing. 

One person I know called my Chip Amp project in a box lid the Pizza Box amp, so the name stuck for this type of project. 

I have some Mogami Star Quad shielded cable to use when I get new XLR Female chassis connectors.

[HAL]

The two SMPS for +/-36VDC at 16.7A is up and running.  These have fans so they can run both 250W amp modules simultaneously. 

The wiring is 14awg for DC power, so might try remoting the two SMPS in another pizza box for EMI/RFI reduction to the amp wiring.

[orchardaudio]

The two SMPS for +/-36VDC at 16.7A is up and running.  These have fans so they can run both 250W amp modules simultaneously. 

The wiring is 14awg for DC power, so might try remoting the two SMPS in another pizza box for EMI/RFI reduction to the amp wiring.

If those SMSPS have adjust pot see if you can get +/-40 out of them to get a bit more headroom.

[HAL]

Yes, they have an adjustment pot.  Will see what the range is with changes.

About ready to try it with higher current loads, so will see what adjustment range I can get.

[artur9]

I look forward to hearing which brand pizza box sounds the best.   

[uncola]

"might try remoting the two SMPS in another pizza box for EMI/RFI reduction to the amp wiring."

dual chassis amp?  now you've really entered the high end 

[HAL]

The input and output wiring is done in the two channel pizza box.   Easy enough to go dual mono, just add one more pizza box.

Will put a seperator between the channels.

Now for connection to the SMPS to try them out.  Yes they are going in another pizza box. 

[HAL]

Pizza Box Amp +/-36V@16.7A SMPS ready for wiring to the amp modules.  Using 14awg stranded Belden 1309 cables for the DC power.

Will add a capacitor bank to the amp module pizza box to lower the impedance at the amp end and help filter any SMPS noise further.

[whydontumarryit]

This is like the 21st century version of SET.
Will the amps overheat if you close the lid?

BTW, headroom is strictly class ab where triple the rated power is on tap. From a regulated PS, I don't think so, that's why 250W minimum is the cutoff point for class D.

[HAL]

The GaN devices are fine up to 200C, so I doubt that the lid closed will be a big deal.  If so, then put a screen mesh on the top for heat escape.  An IR thermometer will tell.

Only if the load is 8 ohms would it be 250W.  It will double to 500W into 4 Ohms and 2 Ohm stable, so yes, the headroom is needed for two amps running 4 Ohm or lower loads.

[orchardaudio]

The GaN devices are fine up to 200C, so I doubt that the lid closed will be a big deal.  If so, then put a screen mesh on the top for heat escape.  An IR thermometer will tell.

Only if the load is 8 ohms would it be 250W.  It will double to 500W into 4 Ohms and 2 Ohm stable, so yes, the headroom is needed for two amps running 4 Ohm or lower loads.

The overtemperature protection kicks in at ~80C. Even though the GaN devices can handle higher temperatures there are many parts close to them that cannot.

[whydontumarryit]

The overtemperature protection kicks in at ~80C. Even though the GaN devices can handle higher temperatures there are many parts close to them that cannot.

80c sounds okay before thermal protection kicks in. 200c for even a moment being something that sounds reasonable is why this attraction to the business of hi-end (expert) audio escapes me.

[HAL]

The overtemperature protection kicks in at ~80C. Even though the GaN devices can handle higher temperatures there are many parts close to them that cannot.

So 80C is 176F for the other parts and I understand as even good electrolytics are 105C rated for some number of hours.  The heatsink is on the bottom of the pc board, so will vent the top and bottom for air flow. 

Would rather deal with that then having to deal with SET heat output to other posted mentions.  No need for extra air conditioning to deal with the heat loads.