Hi everyone. I want to build my first own Subwoofer for home cinema and music. I plan to use a TPA3255 for it and chose a "Hertz S 300 S4" (https://hertz-audio.com/product/car-audio-subwoofers-uno-s300s4/) (I know it is a car subwoofer, but thats the one I already had).
My question now though is: How to design the Power Supply? For low frequencies and this chassis I need some power so toroidal transformer are large, heavy and expensive. That's why I chose a switching power supply. The next thing would now to add a filter and for toroidal transformers you would need to filter 100/120Hz very much. But the switching noise of the switching supply would be at i.e. 80kHz or more right? Even if that is not filtered at all, the chassis wouldn't be able to play that frequencies PLUS nobody would be able to hear it anyway. So what filter should I build? No filtering or just the internal filter of the switching supply seems wrong. Maybe there is no way around powering some load and measure the frequency spectrum to see where the noise is and filter that? Or just use a low-pass like it would be a toroidal transformer and that blocks everything above as well?
I get why switching power supplies aren't very popular in audio environments but for a subwoofer which only plays below 150 Hz or less? Why would you not use a switching power supply?
I'd be happy for every helping anwser.
greetings from Germany,
Michael
My question now though is: How to design the Power Supply? For low frequencies and this chassis I need some power so toroidal transformer are large, heavy and expensive. That's why I chose a switching power supply. The next thing would now to add a filter and for toroidal transformers you would need to filter 100/120Hz very much. But the switching noise of the switching supply would be at i.e. 80kHz or more right? Even if that is not filtered at all, the chassis wouldn't be able to play that frequencies PLUS nobody would be able to hear it anyway. So what filter should I build? No filtering or just the internal filter of the switching supply seems wrong. Maybe there is no way around powering some load and measure the frequency spectrum to see where the noise is and filter that? Or just use a low-pass like it would be a toroidal transformer and that blocks everything above as well?
I get why switching power supplies aren't very popular in audio environments but for a subwoofer which only plays below 150 Hz or less? Why would you not use a switching power supply?
I'd be happy for every helping anwser.
greetings from Germany,
Michael
Is this for a touring band? No, you say "home".
For a mere 250W load, I would totally use a big iron 50/60Hz transformer. When younger I hauled 750W of tube amps every weekend, square irons.
For a mere 250W load, I would totally use a big iron 50/60Hz transformer. When younger I hauled 750W of tube amps every weekend, square irons.
You can design a linear, iron transformer supply.
You can not design a switching type on, but of course you can buy a suitable one ready made.
So make your choice.
You can not design a switching type on, but of course you can buy a suitable one ready made.
So make your choice.
There is an issue with class-D amps, ie they dump power back and forth between the + and - supply, which can cause the supply voltage to surge. But of course, this is not a problem with single supplies like those used with bridged (BTL) amps. Even if it has a split supply, it may be assumed that the dumping is symmetrical for a BTL amp, so it is not a problem. Aside from that, a big storage capacitor allows huge current peaks above the current limits of a PWM supply. Noise should not be a problem but there is no guarantee that a cheap PWM supply is grounded and shielded properly, or that the user will connect the proper grounding. In a SMPS, the safety ground is not just a safety ground. It is also a common mode zero-volt noise reference for the input filter, so an earth ground is not optional. The Y-caps in an ungrounded line filter put half the line voltage on the system ground. SWPS are popular in professional products, but these pitfalls make them unpopular with amateurs.