I am not a fan of talking on the phone, but I love talking to my brothers. We are separated by about 1,071 miles of I-95 which limits our opportunities to hang out. One of the many things we have in common is a love of video games. Recently, we all started playing games online together which allows us to spend a few hours screwing around and the distance, seemingly, disappears. It is like we are sitting in the same room talking and playing video games. I love it.
I do have one little problem, though, the USB headphone/mic combo that I picked up to use with my PS3 just doesn’t get loud enough. This is not just my complaint, but one that I have seen in plenty of reviews online. I knew the fix was simple, so I set out to make a headphone amp.
My requirements are pretty simple:
- low power - I want to be able to power it with readily available batteries.
- good sound
- more volume than I have now.
After some research I settled on the TDA2822M headphone amp ic by STMicroelectronics. This ic was designed as a low power ( 1.8 - 15 Vdc ) dual channel audio amplifier used in portable cassette players and car radios which makes it the perfect solution for my needs.
Here is the example circuit as included in the datasheet:
This test circuit works, however it is fixed gain ( and loud at that ) so I added a 50k stereo potentiometer ( audio taper ) before the input to the ic. While this works great, it does introduce radio signals in its current state, especially when I touch the potentiometers housing. When I solder the final version to a pcb and put it in a case I will likely add some copper shielding to the case to block the radio signals.
Here is the circuit with the addition of the potentiometer:
I have breadboarded the circuit and used it a few times while playing with great success. Because the mini jacks that I am using have an odd pinout, positionally, I had to make a little breakout board for them. The same goes for the potentiometer, otherwise the two channels of the pot would have been summed together on the breadboard.
So, how did the circuit do when compared to the requirements that I had:
- lower power? - I am running off of 2 AA batteries ( 3 Vdc ). Check!
- good sound? - sounds great. Check!
- more volume? - at 3 V this has almost too much volume. Check!
I would call that a success which means I can take the circuit to the next stage - permanence! I hope to spend a little time soldering up a version that can be used while I take my time designing the pcb and sending it off to get etched at a fabrication house.
I’d really like to make a kit out of this so others can have as much fun as I did.