Item: 25W amplifier/speaker with SLA batteries.
I've done a little bit of modding in there. I doubt the warranty is valid any more, lol.
In case you don't want to read the link about my modding, basically, I just added a wire to the power switch of the amp, sending 12V from the battery to a LM2577 DC/DC boost converter set at 12.5V, which powers my mixer. So far, no explosions or short circuits since July 2015.
So here's my deal. Mains voltage is 240V (supposedly, but it's always lower). There's a transformer inside which is outputting almost exactly 12V, and this 12VAC is rectified and fed directly to the SLA battery. There doesn't seem to be any sort of regulating circuit that I can see, at all.
The SLA battery is two 6V 4.5Ah in series. To the best of my (admittedly poor) knowledge, lead acid batteries are supposed to be pretty robust. But that's not the point.
I want to save a tiny bit of weight in the device, and increase its efficiency a little, by taking out the 240V-12V transformer, and replacing it with a 12V SMPS, of which I have several lying around (old external HDD power supplies).
Would you advise against this? I'll have to say I'm not totally up to speed on battery management so please do educate me on the pros and cons here. I am also aware that SMPS can induce interference in the audio circuits. Is there a way around that?
Later on, I'll also look into replacing the battery with something lighter if it's possible, but that's a future concern. After all, the major amount of the weight is the speaker itself.
TL;DR: I have a transformer directly charging a 12V SLA battery for an amplifier/speaker. I want to replace the transformer with a SMPS.