Electronic – Simple Audio Amp for FPGA audio to PC

audiofpga

I'm working on an FPGA implementation of a retro '80s computer (see http://fpgabee.toptensoftware.com) and am trying to setup some 8-bit audio support. I'm using a sigma-delta DAC and a R/C low-pass filter.

What I currently have is a 3.3 V pin from the FPGA driving a circuit.

If I connect a pair of iPhone headphones I can hear the audio, it's sounds quite good although the volume is a little low.

What I'd like to do however is connect this to my PC for recording or to pass-through to my speakers. I tried connecting the above circuit directly to both line-in and microphone sockets on my sound card but the results were terrible. Nothing audible on the line-in, and very low volume and lots of noise on the microphone socket.

So I'm looking for is a simple circuit (I presume a amp of sorts) that will let me get a clean signal into the PC. I'm not talking about hi-fi quality stuff here – this is 8-bit audio driving a very simple dac.

Best Answer

If you are looking for a simple audio interface with volume control, you can do a quick search on internet for such, but if you want recommendation based on personal experience, I would suggest LM4811, which is a simple, low cost and easy to use headphone amplifier from TI. Typical connection diagram for LM4811

http://www.ti.com/product/lm4811

If you work for a company, you can register at TI and ask for a couple of samples. They are not easy to solder, but you may ask someone for help to get it on a test board.