While in high school, I bought a really cool rack mount amplifier at a garage sale. It was branded Queon, and had lots of inputs – it was great. It was supplemented during my university years with an 8-track player/amp combo, acquired from Value Village. The Queon met its end when a roommates’ cat knocked over a vessel of water that had been rested on top of the amp. The 8-track player/amp combo met its end in a post-university move.
I’m not an audiophile, and have been using PC speakers ever since. They sound OK, but:
- The volume control always seems to fail
- The permanently wired connections seem to fail
- Sometimes, it is nice to listen to the radio
- The bluetooth connectivity of little portable speakers is pretty handy
- DLNA / Airplay / Google Casting functionality is also pretty neat
So what I want is an amp for some bookshelf speakers that have been sitting unused. My ideal amp:
- has a volume control
- has a minimum of 4 inputs (PC, radio, Bluetooth, DLNA or alternative)
- has a remote
- is smaller rather than bigger
As most people are looking for home theater systems, there’s not much around that meets this criteria. I have looked at inexpensive amplifiers from Amazon, such as the Lepai LP-2020, but it only has a single input. I came across a place called Shenzen Audio, which had all sorts of neat audio products, but it’s hard for me to order something >$100 from completely unknown brands. The Teac AI-301DA is what I want, but more than I’m willing to pay – I can sacrifice on audio quality and power.
So, I’m going to put together my own. I’m going to pick an off-the-shelf amplifier module, and connect it to an audio switch, add a micro-controller to control the inputs and volume. I’m even thinking of adding an “auto-input” switch, which tries to auto-switch to the intended input (there must be a reason amps don’t do this – I’ll find out when I try).
I’m sure I just don’t know how to search, but I’m surprised how little I could find about such circuits. The best article I read was “How-To: Make a solid-state A/V switcher” on Engadget, but I wanted to avoid soldering surface mount components. There are many switching chips out there, I found it challenging to pick out a basic one. I also considered just using a mechanical switch, but decided I wanted the option of using a remote.
Finally, I decided to use an older design using a chip called a 4066. A number of forums indicate that the audio quality of designs using this chip is poor, but I tried it out – it sounded fine to my ears. It will be hard to tell for sure until it’s done, but there’s always an opportunity to replace it in future revisions.