It isn't a soo good idea to use two different SMPS in series, especally if they are two different ones. They will regulate each other out at some point and since they are in series, the current is the same through both which means the current is limited by the weaker one and you add the noise of both. The heat dissipation is also an issue with them mounted that close to each other.
My countermeasures: to use almost similar current rated SMPS as follows, 15V,5A and 19V, 4.8A. These SMPS are made by same manufacturer and current rating difference is only 0.2A.
I added a 120microH troidal coil which can suppress more than 60dB switching noise from SMPS (see circuit schematic).
Because of Class-D amp, power consumption is depend on sound output power. The SMPS do not generate big heat dissipation in my usual listening environment.
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The fact it's the same manufacturer doesn't make a difference. The problem is, you don't know if they behave identically under load or other circumstances. What will happen if one flukes out? You're doubling the points of failure. The 19V/4,8A one has to deliver 91,2W, the 15V/5A 72W at full current. The enclosure of them looks very similar and it can be assumed the heat dissipation abilitiy doesn't differ by much, which means the thermal stress of the 19V one will be higher than the 15V one.
I've seen it. It's not only about the normal noise, most of these Laptop SMPS' do also clicking noises which will likely still be audible and very annoying (at least for me), you're doubling the times they happen. Well, try it, maybe it works for you, I'd go for a single (and probably different) SMPS though.
Well, that might change and be honest, will you remember that if you're throwing a spontanous party? But if you don't use that much power, you can use one PS, the IC starts to work at 18V.
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