Construction date: September 8, 2013 – October 5,2013
Time to build: 12 hours
New update 4/21/2014
I have recently added a Bluetooth to the amp internally. The model I chose was a RN-52 Bluetooth 3.0 module as it looked to be the easiest to integrate and needed minimal programming. In this application I did not even need to change the firmware. I also installed a input selector switch, fixed up the internal ground, added a power switch and power LED to finish off the amp. I can’t seem to find a picture at the moment to show you but the Bluetooth needed a isolated power supply. I chose a Recom isolated dc-dc converter for the job and it worked like charm. The ground feedback loop was eliminated and it was nothing but pure sound from the amp.
Some of the new features include:
- 3 way input this includes RCA, Internal Bluetooth and 3.5 headset jack
- A star ground
- A power switch with green power led
- A internally isolated HiFi Bluetooth module
- Very clean power filtering is provided by hand selected Muse capacitors in many areas of the amp.
During testing of the internal Bluetooth
I have now completed building the speaker boxes and the enclosure though I still need to mount some terminals in the box but other then that its working, future improvements may include a USB input and a input select switch.
My work office sometimes is a bit to grey. That is the best way to put it so I though I would build a speaker system for it and if they don’t like me having it there I can always put it downstairs in my new lab. Below are some pictures of the the progress so far. I have made the amp section from a chip amp kit. I have modified the components slightly by replacing a few of the capacitors with audiophile grade ones. I have also used silver solder for all of the construction and I plan on getting a case to put the amp in. The transformer is from eBay and the aluminum heat-sink was found at a local computer store scrap box. The LM386 analog ships are mounted to the heat-sink with Allen key model car screws and nuts and a thermal compound. There is also a ceramic pad between the chips and the heat-sink.
Here is a link to the kit I used: http://chipamp.com/lm1875-amplifier-kit/
Be careful if you are new to kits as these only come as boards and components for the amps, you still need to wire in a transformer, volume control, find a case and wire up external connection plugs.
I wanted to also build some matching speakers for the system so I bought two Tang Band W4-1320SJ 4″ Bamboo Cone Drivers and a pair of nice fabric tweeters for a more high range sparkle. Currently I’m having my brother and law build the speaker boxes out of 5/8 inch birch plywood. I plan to have them finished with hand rubbed oil for a more natural look. The speaker boxes contain a internal baffle and are ported for better bass response. I will post a picture of the speaker boxes as soon as I have them. A picture of a 3d model of the cabinets is below.