linear unregulated PSU for 3e-audio tpa3255

[cbueche]

Hello everyone,

I'm in need of an amplifier for a friend. I want to try class-D, she's looking at limiting her power consumption so class-D seems a natural choice. I have seen the 3e-audio tpa3255, but I'm not sure about the PSU. I have a toroid that are specified at 180VA, 2x12V@8A. I can serialize the windings to get 24V AC, which after full-bridge rectification will provide 32-33V DC.

I'm not sure to understand the spec of the 3e-audio TPA3255-2CH-260W product in regards to power supply, it says "Single supply voltage range 24V~51V(UVP:24V)". I understand I won't get its full power but it's not a problem, the TABAQ I made for her do not need much power anyway. She drives the setup with a bluetooth receiver, and the amp will only have a volume pot between the RCA input and the board.

So my questions

• what is "UVP:24V" ?
• will this amp work fine with ~32V DC
• is the unregulated DC a problem ?

I shall mention that I already have rectifiers and capacitors (10'000 uF, 50V) and even a PCB, so if this PSU is ok I have little costs besides some casing. Can I just add say 4 of these caps and maybe some smaller cap in parallel ?

Thanks for your hints !
Charles

 

[jan.didden]

UVP normally means Under-Voltage Protection, it is the lowest supply it will work on. Lower than that and it will shut off.

The higher the supply voltage, the higher the power that can be delivered but with those speakers, 32VDC should deliver ample loudness. And reliability will be much better than with very high supplies.

Jan

 

[joensd]

32V is plenty enough for the given speaker.
See the datasheet of the TPA3255 p.11.

I had a 3" Tangband and they can´t take lots of power anyway.

That said, use what you´ve got and go for the 3e-board.
I only heard good things about it and sound quality is supposed to be better than the older lower-power variants. (TPA3116,3118 etc.)
Plus, your friend is safe if she should change speakers in the future.

 

[cbueche]

Thank you Jan and "joensd". Now I only need to wait the 3e-audio order to be delivered and plug the thing together. Looking forward to hear my Tabaq on class-D.

 

[CharlieLaub]

I would make sure your (or anyone trying this) linear PS has enough capacitance to handle full power and keep the voltage sag low enough so that it doesn't trip the UVP. If you don't plan to use the amp at high output power this will not be a concern, but I thought I would mention it.

Edit: I see you have four 10kuF caps. Using all four of them should work OK, depending on how close to the UVP limit your PS will operate when unloaded. At 32VDC you should be fine.

 

[cbueche]

Hi Charlie,
thanks for your input. I will do some measurements on a dummy load and see what DC sagging I have, and keep adding capacitors if needed. The power-on pulse might at some point become an issue, maybe I'll use a small Resistor between the diode bridge and first capacitor, with a relay to shorten it after 5-10 sec.