Pizza Box v2.0 Class D amp project

[HAL]

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

Attachments

[brombo]

You may want to look at these cabinets -

https://www.amazon.com/Zulkit-Electronic-Enclosures-Enclosure-Preventive/dp/B08BS243RC/ref=pd_bxgy_vft_none_sccl_2/139-0457158-0358626?pd_rd_w=2dHLB&content-id=amzn1.sym.26a5c67f-1a30-486b-bb90-b523ad38d5a0&pf_rd_p=26a5c67f-1a30-486b-bb90-b523ad38d5a0&pf_rd_r=5CXQYK7DFNQAY21K1SRS&pd_rd_wg=1X3uE&pd_rd_r=7530b91e-cd55-4d5f-90d9-b3c9d632429a&pd_rd_i=B08BS243RC&th=1

[tomp]

Rich: Here is the schematic of the soft start I have been using for 25 years. Some of the components may have been replaced by newer versions, but the concept is still the same. It first checks the line voltage to make sure it is not too low or high and then starts a phase control circuit to gradually increase the phase angle and thus the power. Once at full phase angle, the phase control circuit is bypassed and turned off to eliminate switching noise.

Attachments

AC Soft Start.pdf

(54.38 KiB) Downloaded 549 times

[HAL]

Rich: Here is the schematic of the soft start I have been using for 25 years. Some of the components may have been replaced by newer versions, but the concept is still the same. It first checks the line voltage to make sure it is not too low or high and then starts a phase control circuit to gradually increase the phase angle and thus the power. Once at full phase angle, the phase control circuit is bypassed and turned off to eliminate switching noise.

Tom,
Was going to look at this soon. I am sure it will need it.

Did find some GaN FET's to use as a sub for the Power MOSFET. Have two here to try in the circuit. About the same price and lower losses in the device. Heatsink will be tiny as they can run up to 200C and very efficient.

[HAL]

You may want to look at these cabinets -

https://www.amazon.com/Zulkit-Electronic-Enclosures-Enclosure-Preventive/dp/B08BS243RC/ref=pd_bxgy_vft_none_sccl_2/139-0457158-0358626?pd_rd_w=2dHLB&content-id=amzn1.sym.26a5c67f-1a30-486b-bb90-b523ad38d5a0&pf_rd_p=26a5c67f-1a30-486b-bb90-b523ad38d5a0&pf_rd_r=5CXQYK7DFNQAY21K1SRS&pd_rd_wg=1X3uE&pd_rd_r=7530b91e-cd55-4d5f-90d9-b3c9d632429a&pd_rd_i=B08BS243RC&th=1

Thanks! Will take a look.

[DaveR]

I'm using power supplies I purchased from hifimediy.com. I can't speak to all they offer, but the ones I'm using have built in soft start, two 12 VDC auxiliary outputs for low voltage stuff and a low voltage low current contact closure terminals to turn them on and off.

[SoundMods]

Rich: Here is the schematic of the soft start I have been using for 25 years. Some of the components may have been replaced by newer versions, but the concept is still the same. It first checks the line voltage to make sure it is not too low or high and then starts a phase control circuit to gradually increase the phase angle and thus the power. Once at full phase angle, the phase control circuit is bypassed and turned off to eliminate switching noise.

YIKES! Could it be anymore complex?! How about a time-delay relay and a series resistor? The K.I.S.S. method does have merit.

[tomp]

Yes, I have built some soft starts with a resistor and relay and they worked OK. Simple and cheap. The advantage of what I showed is that you are not dependent on resistor/load combination. You can use any loads and the current limiting is the same. I run almost all my stuff through it. Another advantage is the whole system will drop out if there is a significant surge or sag in the line voltage protecting all the devices. There is also a section with no soft start for some of the digital devices where the displays will not come on if the voltage ramps up slowly. So yes it is complicated but I only had to build it one time and have used it wtih many different devices. It also has run flawlessly for 25 years. So I consider it worth it.

[HAL]

Tom,
I think I will adapt your soft start circuit and use an Arduino uC for the control and timing. At $20 and easy programming would be an interesting project. Easy to drive power MOSFET's for relay control directly from the 8 channel digital output with a pull up resistor. Already used one I reprogrammed as a DAC volume controller.

Already have the software development system on the laptop, so for a really hot day this summer will be time to investigate.

Not happening soon. Just had the rear of the house regraded after 29 years as it was sinking toward the house. That side foundation drain replacement did not solve the water problem, so this is fix #2. Last looks like needing an active sump pump system as none was ever installed for that room 2ft below grade during the house build. Phone calls to get a sump pump install estimates have begun. UGH!

[tomp]

Rich:

Design went the way it did because in 1998, Arduino was not around. If I were 20 years younger I would learn all the programming you know and do many things differently including a truly smart controller for load shedding with my whole house generator. There are some amazing latching relays out there for not a lot of money. You could build in priorities for loads, measure total loads and individual contributions for the major loads, and if loads were shed you could calculate the effect of adding back a high priority load taking into account start up surges. Using latching relays, no power would be drawn for the majority of the time when you were not on generator. The "smart" transfer switches that Generac sells are really incredibly stupid and also use power contactors for accessory loads where the coils have to be energized all the time until an outage. That is a terrible waste of power.