I had a need for a 5V amplifier, and a quick search showed the easiest commonly available module is based upon the PAM8403, and cost about $0.50 per unit.
10 Pcs PAM8403 2X3W Mini Audio Class D Amplifier Board 2 5 5V Input US SHIP M323 | eBay
Having played with these for a few days now, I can safely say, if you only need a few watts, you will not find a better amplifier for under $1.00. The sound is very good, and the board layout is not terrible. However that is not what this thread is about, just a bit of back story.
After being very satisfied with these I looked into other Diodes inc PAM based amplifiers, and discovered the PAM8406 which is pin compatable, supports down to 2R loads at 5W/ch running 5V. That is all well and good, but you might be saying "I don't use any 2R speakers that will run well at 5W", and you would be correct. The real thing about this chip that caught my eye, was the "mode" selection that the PAM8403 does not have. This chip can be operated in Class AB mode!
After inspecting the layout for the $0.50 boards, I found the mode pin (listed as NC for PAM8403), is already tied to ground, so a simple chip swap will give a PAM8406 amp ready to run in Class AB. So that is what I did, and I can report that it is a fairly significant upgrade from the PAM8403, at the cost of a much lower efficiency.
Now, since this chip is such a simple layout, I thought maybe I can do better, which brings me to the real reason for this thread. I have done an initial layout for a PAM stamp, and would like some feedback. I based my layout on the Chinese board, but made several improvements.
1.) Increased input decoupling. Was already fairly good, but can always be better.
2.) Eliminated external 10kR resistor from input, instead relying on input impedence to form the input filter.
3.) Added ground plane everywhere for noise suppression and EMI
4.) Added ferrite bead filter on the output for EMI
5.) Cleaned up the input and output headers (IMO, this is a personal preference thing)
Please note in these photos, the signal input ground should connect to the ground planes surrounding it, I need to fix the copper there. The bottom of the board is a solid ground plane.
Would love to hear the opinion of those with more experience laying out boards, I basically have no clue what I am doing. I will try to get some high res pics of the Chinese board I started with for comparison tomorrow. I can post component values for the passives if anyone wants to know.
10 Pcs PAM8403 2X3W Mini Audio Class D Amplifier Board 2 5 5V Input US SHIP M323 | eBay
Having played with these for a few days now, I can safely say, if you only need a few watts, you will not find a better amplifier for under $1.00. The sound is very good, and the board layout is not terrible. However that is not what this thread is about, just a bit of back story.
After being very satisfied with these I looked into other Diodes inc PAM based amplifiers, and discovered the PAM8406 which is pin compatable, supports down to 2R loads at 5W/ch running 5V. That is all well and good, but you might be saying "I don't use any 2R speakers that will run well at 5W", and you would be correct. The real thing about this chip that caught my eye, was the "mode" selection that the PAM8403 does not have. This chip can be operated in Class AB mode!
After inspecting the layout for the $0.50 boards, I found the mode pin (listed as NC for PAM8403), is already tied to ground, so a simple chip swap will give a PAM8406 amp ready to run in Class AB. So that is what I did, and I can report that it is a fairly significant upgrade from the PAM8403, at the cost of a much lower efficiency.
Now, since this chip is such a simple layout, I thought maybe I can do better, which brings me to the real reason for this thread. I have done an initial layout for a PAM stamp, and would like some feedback. I based my layout on the Chinese board, but made several improvements.
1.) Increased input decoupling. Was already fairly good, but can always be better.
2.) Eliminated external 10kR resistor from input, instead relying on input impedence to form the input filter.
3.) Added ground plane everywhere for noise suppression and EMI
4.) Added ferrite bead filter on the output for EMI
5.) Cleaned up the input and output headers (IMO, this is a personal preference thing)
Please note in these photos, the signal input ground should connect to the ground planes surrounding it, I need to fix the copper there. The bottom of the board is a solid ground plane.
Would love to hear the opinion of those with more experience laying out boards, I basically have no clue what I am doing. I will try to get some high res pics of the Chinese board I started with for comparison tomorrow. I can post component values for the passives if anyone wants to know.