Why cant I use SMPS for TPA3255?

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wonderfulaudio

Member
Joined 2018
#1
Hi,

I just bought two pieces of Aiyima 07 TPA3255 amplifiers and also bought 48V SMPS for them. But later learnt that the manufacturer advises not to use SMPS for it but use power adapter instead. Well, first of all, what's the difference between them, technically both are SMPS only?
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Thanks and Regards,
WonderfulAudio
 
#3
With any class D amp you don't want intermodulation with other high frequency oscillators such as a SMPS's oscillator - if any IM product ends up in the audio band and not sufficiently filtered out it will be audible... Its smart to run SMPS and class D oscillators synchronously, just as multiple class-D's in the same box should be synchronized or chosen carefully so that no IM products fall below 20kHz...
 
#6
I suspect that the manufacturer of the amplifier is simply concerned about fire safety. As I recall, the amplifier does not have a power supply fuse because the current limiting function was transferred to the power supply. If you use an industrial power supply of 20A or 40A, then the current protection on the power supply side changes greatly, and the amplifier can simply catch fire when a microcircuit or capacitor breaks down.
 
#7
"Industrial" SMPS don't have to meet the same emissions specs as for home use power supplies. Maybe a medical grade SMPS from Meanwell or something like that could tried. Also, some physical separation and or shielding between the power supply and the amplifier might help. One could try it and see.

Otherwise, regulated 48v, 7A linear power supplies are not necessarily cheap, small size, nor necessarily light weight. Maybe an unregulated linear 48v supply with some added linear regulation on heat sinks could used. Or, maybe a used bench supply from ebay?
 
#8
The power supplies that everyone uses with these amplifiers are SMPS. I have no idea what the manufacturer is talking about. Even the power adapters they provide are SMPS and sometimes using GaN transistors for greater efficiency. You only use GaN transistors in SMPS so that's proof enough that the bricks they provide are SMPS.

The TPA32xx amplifiers use large amounts of feedback in a closed loop configuration with better implementations using post filter feedback. This makes the amplifiers pretty insensitive to what power supply they are used with and you'd need something of heroically bad performance to reduce the performance of the amplifier in any meaningful way.
 
#10
jean-paul said:
You could ask yourself if you really need that bizarre high output power. Even with deafening volume you will not use more than a few Watts.
Click to expand...
As I said I need 200W+200W RMS for dual subs. During short moments of sub peaks they will definitely be required to supply about this power, maybe not always as music does not have continuous bass but intermittent only
Warm Regards,
WonderfulAudio
 
#11
The 48V supply would definitely give you more headroom when compared to the 36V supply. If you want to fully capitalise on this headroom, the current rating of the 48V supply should be proportionally higher, since impedance is constant. However, if you're on a budget, adding a large bank of bus capacitors would certainly help during short loud bursts of sound, like dinosaurs or thunder.
 
#12
Not many SMPS tolerate a bank of capacitors. I have some experience with very high power 48V DC systems. High DC currents can be pretty destructive when something goes wrong. Does not like DC jack connectors either but sturdy high current connectors. It maybe is a good idea to use a high power 48V 10A SMPS (one without overshoot) and the amplifier hardwired in 1 larger well ventilated casing like once was standard.
 
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