Rebuild of my first Class D Amplifier - Plz Help

[nelson_mendes]

Hello everyone,

This is my first post on the diyAudio forum so I think it would be nice of mu behalf if I present myself to all of you.

My name is Nelson Fernandes, I'm 27 and I'm Portuguese.
I'm finishing the Master in Electrical and Computers Engineering, field of Automation and Energy. A year ago, due to my activity on ebay I've opened my eyes to the Audiophile area by buying a TA2024 Sure Electronics board. I just loved the sound of it and even modified it with some of the advices at JustBlair's webpage and build a digital volume control for it, based on the Kookabura project.

So here's a photo of what was my first Class D Amplifier:

An externally hosted image should be here but it was not working when we last tested it.

You can see that it's very small and all of it's space is, on my opinion, well used.
The bad news is that it's no longer among us... Thanks to my mother, her cleaning mob and my ingenuity when I built the variable power supply that feeds the amplifier.

I'm pretty much desperate to ear again music while working, resting and sleeping with the quality that I was used to and I'm in process to rebuild it but I'm uncertain of what to do, and for that I need some expertize help.

I don't want to spend much money, since it's part of the spirit of this hobby for me. Also I'm very busy on a daily base and I wouldn't like to spend productive time on this. I could simply buy the same board and modify it again, but the Sure's board it's tricky and I think for the same money I can get better.

The Argen Helder TA2024 MKII is a possibility, but I don't know if I can get one already with 2.2uF input capacitors. This board is better to modify and that's what leans me towards to it.

The board that burned, after the changes I've made measured 97x66x18mm so anything more complete would be necessarily bigger and much bigger is not a choice... The box is completely done, the space for the digital volume control is reserved... I really would like to rebuild all inside the same box because the hole thing has already a sentimental value for me.

I looked for some TA2020 options and I don't know if the extra power on 8 Ohm speakers compensates the extra work that would be necessary to modify it and place it inside the box.
They are:
NEW Tripath DIY Audio TA2024 PCB Stereo Amplifier Board - eBay (item 330503446727 end time Dec-04-10 23:40:28 PST)

New MKIII Tripath TA2020 PCB 25watt Class-T amplifier - eBay (item 330502483959 end time Dec-02-10 21:00:13 PST)

More power than the TA2020 is a bit out of question because I have the audio set inside my room and it's not very spacious. Maybe for a next project when I have my house and a nice living room...

So, resuming... Small room, 8 Ohm - 80 W - 2 way - 91db speakers, digital volume control usage, small pcb to use the same little box...

What are your advices on this? Argen Helder MKII or anything else?


Thank you so much for your time and attention.


Best Regards from Portugal,

Nelson

 

[nelson_mendes]

Today I thought more and maybe is better to buy a low power finished product.
Also I should use the old box to put there a voltage protection to the amplifier (PIC based) in order to never burn an amplifier again with voltage excess.

So, I'm using this thread to ask you what is, in on your opinion, the best buy on low power class D amplifiers. This is valid for generic boards without much to modify and boxed products with the following requirements:
- Input with RCA plugs.
- Space inside for somehow place a pcb with 64x39x25mm (the digital volume control)

For the board option, I'm undecided between Argen Helder TA2020 MKIII and this one:
TA2020 Class T Audio Amplifier 20W T-AMP NEW - eBay (item 260689690861 end time Dec-08-10 00:47:02 PST)
anyone has it?

For the interested ones, I leave you a photo of my digital volume control:

An externally hosted image should be here but it was not working when we last tested it.

It uses a PIC12F683, PGA2311, OPA4228 and a little SMPS for +5/-5V.
It works great and with this I won't ear the pot noise when it gets old, so I think it's a good idea to maintain it on the project... Anyone agrees?

Thanks again for your time and I'll look forward to see your answers...
Don't be shy to say I'm doing all wrong... Believe me when I say your opinion will be always appreciated and I'm here to learn my first steps on this great hobby!

Best Regards,

Nelson
​

 

[superR]

I assume that you use a pot to send a voltage between 0 and 5 Vdc to the pic and translate that value to a SPI signal for the PGA2311?
I would be interested in the schematics of the volume control and the code of the pic. If you would share those, please do!

 

[nigelwright7557]

I assume that you use a pot to send a voltage between 0 and 5 Vdc to the pic and translate that value to a SPI signal for the PGA2311?
I would be interested in the schematics of the volume control and the code of the pic. If you would share those, please do!

I just used the cheapest PIC and used 2 I/O pins to check the output voltage via potential dividers. The i/o threshold of PIC is about 2 volts.
If i sensed a high voltage or low voltage for more than 500ms I assume a fault and turn off the output relay.

 

[superR]

But do you use it to drive the PGA chip as well or does an external device do that?

 

[nigelwright7557]

But do you use it to drive the PGA chip as well or does an external device do that?

What does the PGA chip do ?

I forgot to add in my last post the PIC also holds off the relay for 3 seconds on power up.

 

[Lingwendil]

Any chance you'd be willing to share your code? I'm building a circuit using the same volume chip and a PIC16F684 or PIC12F68 PIC chip.

 

[superR]

That would be like sending my local tvguide to the us. It is specific to my programmer and therefore unusable for non arduino's. And by the way, it's a mess so shouldn't be used as an example. As soon as you figure out how to send SPI signals with your PIC, you're set!

 

[superR]

Never mind, I thought you were writing to me Different thread