@Samsonio I found a potential solution from the Yongzhuxing website:
https://www.yongzhuxing.com/goods.php?id=296
"If some power amplifier boards have poor noise suppression, it is easy to cause static noise. The solution is actually very simple. Add a dummy load between the output +VCC and the ground, such as a high-power cement resistor. The specific amount of improvement is determined by the experiment, because different boards will be different. The maximum operating voltage of the matching power amplifier board must be lower than 90% of the maximum output voltage of the switching power supply. Then, when the switching power supply is at the highest voltage output, the waveform is the cleanest when it is static." (translated via Chrome from Chinese)
This raises two questions:
- What would be a good starting value for the dummy resistor?
- I'm considering buying one of these 600W PFC/LLC power supplies myself to use with my Aiyima A07 Pro (Class D amp, max 48V). However, I'm confused about the recommended output voltage of the power supply.
According to the hint, your amp's max voltage should stay below 90% of the PSU's maximum output voltage. But then I found a guide on the same site (
https://www.yongzhuxing.com/article.php?id=155) that seems to suggest lower voltages for amplifiers. For example, they recommend 28-36V PSU for a TDA8954 amp (±42V), explaining that:
"It is recommended to choose 28-36V. In fact, it can be fine-tuned to about 40V. It is not recommended to choose 36-50V, because the switching power supply will be frequently shut down when lightly loaded, and a dummy load needs to be added!" (translated via Chrome from Chinese)
This seems to contradict the previous hint, even though the guide is linked in the hint. The explanation in the guide, however, makes more sense than the recommendation in the hint. So, I'm wondering if this could be a translation error.
Conclusion:
I'm leaning toward a 36V PSU for my Aiyima, even though it's rated for 48V. What do you think?
Lastly, I found two different versions of the 600W PFC/LLC single-voltage power supplies:
Does anyone know if there’s any difference between them aside from the dimensions?
Unless I misunderstand, his issue has no relation to the "poor noise suppression" solution the manufacturer references. They are referencing a ripple & noise level (probably excessively high) that is affecting an amp board with inherently poor PSSR.
Every once in a while you get a power supply that does not "play nice" with a particular amp module, it happens. I recently had a conversation with a manufacturer about a top of the line Meanwell supply that had a small issue with a superb high end amp module. Cheap/crappy power supplies on the other hand have a habit of doing strange things like this gentlemen is reporting.
edit:
looking into it further it seems this manufacturer is also warning you about a required MINIMUM load for the unit to operate correctly. Normally a supplies white paper will list a required minimum load expressed as a percentage of the rated maximum load. If you run it UNDER this amount bad things will happen..
a made up example:
a brand ABC supply 600W rated max power output, a 5% minimum load rating = 30W
using a single 3eAudio 2 ch module, idle power is about 6.1W (quiescent power)
you will have an issue! So they are advising adding a load resistor to reach the required min load (uuummmm no thank you, I will never add unwanted heat into a small amp case, just buy the right damn power supply please)
It may not turn on, it may falter in the output voltage regulation, it may do something else unpleasant.
I can not find any proper spec papers for these Youngzhuxing supplies and the warnings and suggestions they provide give me no confidence in the product design.
the 90% voltage suggestion from them is idiotic, if you can run at 48V, the amp module will probably spec out at around 50V max input to the board, so use a quality 48V REGULATED supply or you will lower the amps maximum power output substantially. I do not play around with cheap power supplies ever as I require quality and reliability/long life.
FYI a good regulated 48V supply will maintain +-1% of stated voltage to max power output so between 47.5V to 48.5V. Nice!
I have now used about 12 Mornsun supplies flawlessly with the 3e amps; lof350, lof450, lof550 and lof750. I think I used the 750W on 3 modules with no issues. I will be testing 3 Orchard Audio starkrimson modules this week (about $475 each) with the lof350 & lof550 supplies as well.
the 2 power supplies noted above from Aliexpress are 2 different form factors 184 x 88mm and 130 x 88mm, no other info is really given.
As always remember that these 600W supplies are likely 200-300W max continuous output, anything above that requires fan cooling
I can find no real documentation for these supplies