When I was looking for a power supply for my BT20A Pro I reached out to Fosi Audio.
Carl responded to me via mail:
"... In terms of power output, both the 48V / 4.4A and 36V / 5.9A variants should provide similar results for your amplifier.
However, there are some factors to consider when choosing between the two options.
The 36V variant may be better for the longevity of the parts used in the amplifier, as it will put less stress on the components due to the lower voltage. However, this may come at the cost of slightly reduced performance. The 48V variant may provide slightly better performance, but could potentially cause more wear and tear on the amplifier components over time.
Ultimately, the decision between the two options will depend on your priorities. If you prioritize longevity and reliability, the 36V variant may be the better choice. If you prioritize performance, the 48V variant may be the better option. ..."
Since I wanted to have a passively cooled power supply and the 200W are sufficient for me, I chose the LRS 36V. Currently I use it for my BT30 Pro (two speakers + passive sub) that accepts max. 36V.
They, fosi Audio, gave you a generic answer to your question. The answer I gave in my post was for specific use cases, taking into account of the OP's speaker impedance.
So, in reality, the fact is, 4 ohms nominal speakers typically may have impedance dip to below 3 ohm, even 2.5, 2 ohms.. So in that case, the 36 V 5.9 A would likely perform better. I gave a slightly more technical answer, because this is a science centric forum, otherwise I would stick with Watts and avoid talking in terms of voltage and current altogether lol..
Power = V^2/|Z|, but also = I^2*|Z|
Assuming an 8 ohm resistive load, 48 V, 4.4 A will give you about 211 W.
whereas the 36 V 5.9 A will give you about 212 W
So in terms of W, they are the same, but again, W is not a good way to look at it, the fact is, 4 ohm nominal speakers with dips to below 3 A, could demand much higher current than 8 ohm nominal speakers, all else being equal, so the 36 V 5.9 A power supply is the preferred one. Your choice..
The 36 V will potential perform better in sound quality, and put less stress on the amp, the 48 V one would lose on both counts. However, the opposite
could be true for 8 ohm nominal speakers depending on how close your actual demand is, to the rated output. If you only push to say 30% of the rated output, then just flip the coin, or still take the 36 V one is you are concerned about the little better longevity of the amp.
