TPA3255 Reference Design Class D Amp with PFFB

[Cresnet]

Plott,
Did Sami give an explanation why the SMPS wasn’t 100% assembled?

The reason for sending the PSU & the heatsink separately is that I don't have the heatsinks here.

So, I had to ship the heatsink separately from the factory and the SMPS from the lab.

The assembly job is pretty easy and takes 10 minutes.

Thanks

 

[Plott]

Many thanks Vunce

 

[Plott]

The reason for sending the PSU & the heatsink separately is that I don't have the heatsinks here.

So, I had to ship the heatsink separately from the factory and the SMPS from the lab.

The assembly job is pretty easy and takes 10 minutes.

Thanks

Thanks Sami again! One thing... I did it in 8 minutes 😀

 

[Cresnet]

Curious what you did with the double-sides blue tape that came with the SMPS. Sami tried to describe where to apply it, but his explanation made no sense to me.

Ignore that thermal pad and just attach the thermal switch directly.

 

[xrk971]

Hi X,
could you please check and correct (if needed) the following wiring plan for the psu?

• Main voltage output with the big connectors: to the amp board, it's clear 🙂
• 12 vdc output to the buffer

Yes, always on 12vdc if IEC mains switched on.

• 3.3 vdc output can be used for an LED on the front with a resistor in series

Yes, choose for 1-2mA current. 2mA might be bright.

• AUX (15 vdc) to the amp board - but in your build (and in the picture above) I see a cap on the top of the connector; is it against turn on bump? If so, which value/voltage is needed?

Yes, to prevent turn off thump. Allows opamps to stay on longer than power amp. Use 2200uF 16v.

• How/where to wire the further contacts (STDBY, DCER, DELAY?)
• PSU input is J1, whit the left contact live and the right contact neutral? Middle contact not in use?

The STDBY goes to switch common. n/o on switch goes to switch LED anode using circa 470R resistor. LED cathode goes the STDBY GND.

Delay provides 2 sec delay and then open collector logic to drive your accessories logic like an output SSR. Etc.

DCER is a warning light to show PSU has error and needs to be reset. Use appropriate resistor and LED circa 1k I think.

• J2 has in your build (and in the above too) a jumper - what is it for?

J2 is jumper for 110-120vac mains. If you are 220-240vac remove it! Or it will blow the amp since PSU will make 2x designed voltage (100v!). It will kill the amp.

• Where can I set the input voltage to 240vac?

See above. Do not install J2.

• mains fuse value at 230vac?

I use 5A to allow for inrush.

• Is the turn on button a locking one or just a push button without locking?

Locking one or latching one.

Get 12v, latching selection.
https://a.aliexpress.com/_mPKGbsW

Really not that much 😀
Many thanks in advance

Good luck!

 

[Vunce]

Data Sheet:
SMPS630-SO_2412020.pdf

 

[Plott]

Many thanks X! I'm really looking forward to complete this amp 🙂
Only the push button is not clear, sorry. Should the switch stay closed after turn on, or does it only give an impulse and remains open?

Thanks @Vunce Sami also sent it short time ago. But the explanation of X (based on his experience) is priceless.

 

[Plott]

And just because it looks so great, here the boards 🙂

 

[xrk971]

Many thanks X! I'm really looking forward to complete this amp 🙂
Only the push button is not clear, sorry. Should the switch stay closed after turn on, or does it only give an impulse and remains open?

Thanks @Vunce Sami also sent it short time ago. But the explanation of X (based on his experience) is priceless.

Latching switch. Not momentary. Because the STDBY connection expects a constant connection to keep amp on.

Connect like this but replace the connection where SSR X1 is with solid connection. The drawing shows how to connect a speaker protect SSR in series. If you remove the SSR it still works as power standby switch. Make the resistor 470ohms though.

https://www.diyaudio.com/community/threads/rtr-ssr-speaker-protection-gb5.392399/page-5

 

[Plott]

Thanks X, now it's clear.

 

[Plott]

Hi X,
just a short clarification please: Nelson uses in his amps a 2.5 A mains fuse for 120vac and 1.25 A for 230vac. Does it mean that I need 2.5 A fuse for 230vac, when you are using a 5 A fuse for 120vac?

 

[xrk971]

Honestly, if you want to size it properly, you need to look at your local electrical code. In the US, I think you are technically allowed to use a fuse rated for the max current plus a margin, I seem to recall margin here in US is 25% or something like that. If we assume amp is max 150w per channel and 2 channels so 300w continuous. 300w/220v is 1.4A x 1.25 margin is is about 1.75A fuse. Closest is 2A I think.

But please check with your local electrical code to see what is allowable. You don’t want to have a system that is not safe. The SMPS has a fusible link (soldered in place slow blow fuse) on the PCB as fail safe.

 

[Plott]

Thanks X, it helps!

 

[Plott]

Hi X,

regarding the reset-switch, am I good to go with a switch rated at 24 vdc 0,1 amps?
Thanks in advance.

 

[xrk971]

Yes, it’s low level logic switch. Momentary contact though.

 

[Plott]

Thanks, I thought so too, but wanted to be sure.

 

[Plott]

Hi X,
another switch-question 🙂
The specification of the mains switch is clear, I will use a 250vac/5amps type.
But what's the requirement for the standby switch on the front? Is it also a low level logic switch, and if so, can I use one with 48v/2amps rating?
Many thanks!

 

[Plott]

...or even 36v/1a?

 

[xrk971]

Yes, low level 12v switch capable of 10mA.

 

[Plott]

Thanks X!