Hi-Fidelity Amplifier

TW Labs HFA-01 - 30 Watts RMS x 2 Channel
Custom Built Hi-Fidelity Audio Amplifier

A Surprising Amplifier in a Small Chassis

One day I was out working in my lab and the computer speakers I had been using as a sound system died.  I was already unhappy with the sound quality and poor acoustic power of the store bought speakers so I decided I would build myself an amplifier to go with a pair of JBL Control 28 surface-mount speakers I had kicking around.  

The end result is the Tumbleweed Labs HFA-01 is a 30 Watt x 2 Hi-Fi amplifier that was 100% custom built from A/C power input to speaker output.  

The case work was salvaged from an old 5.25" external SCSI drive case I scored from RE-PC in Seattle for $7.  The front panel, rear panel and power supply spool and circuit boards were all cut on my Fireball V90 CNC router.  

The design is based on the ST TDA2050 IC (spec sheet) and I must say, the results are pretty spectacular for such a small form-factor chip.  The toroidal transformer and large caps used in the power supply provide plenty of headroom so the amplifier stays strong in the low-end even during particularly "punchy" segments of music.  

Check out the detailed photos below.  I've also included a section where you can download the drawing files, parts list and spec sheets for the parts I used to build the project.  Enjoy!

The front panel is cut from 3/16" A-Grade plywood.  I used an Ultraviolet LED for an indicator light.  I find them less harsh than blue LEDs and they look cool and different from other indicators.  LED, mounting boss and volume knob were sourced from my local Radio Shack.  The stereo potentiometer is al Alps brand which I got from Alphatronics in Tukwila, WA.  

The SCSI case has some nice ventilation built in.  

Here you see the rear panels.  They are also cut from 3/16" plywood and I cut them specifically to cover some holes in the rear of the chassis that would have been used for hard drive connections.  It was really nice that the power input, fuse holder and mains power switch were already built right into the case.  The amp uses a standard IEC power cable.  I lucked out with the two holes in the top of the rear plate and the panel-mount RCA connectors bolted right into them.  RCAs and speakers lugs were sourced from Alphatronics. 

Here you can see the toroidal transformer and power caps.  You also see a side profile of the spool I made to hold the transformer to the chassis.  As a finishing touch I put a couple of blue LEDs inside the case so that while it's operating you can peek in at the internal components.  

Here you see the main wiring harness.  I used a Molex type connector to bus the volume control and indicator light wiring to the front of the cover.  This way if the amp needs to be serviced you can simply unplug the harness and remove the cover.  

Here you get a nice look at the brains of the peration; the TDA2050 chips.  This amplifier operates in stereo but is actually what is known as a dual mono-block amp; meaning there are two totally separate amplifier circuits.  I salvaged this heat-sink from a dead Crown amp I scored from work.  

There is a lot going on in this photo.  You can see in detail the amplifiers and power supply stage.  The two black squares are bridge rectifiers which convert the A/C current to D/C.  They were also salvaged from the Crown amp.  The board you see above the rectifiers is a large filter stage to reduce noise from the power source.  

All boards were mounted with PC motherboard standoffs.  Self-adhesive zip tie holders and terminal blocks are really helpful for this type of project. 

Here's a great view.  Ain't she sexy!?

Lastly I took a perspective shot.  Overall I'm really happy with the way this project turned out.  I took the time to put a lot of love into the layout of the chassis and quality of the build.  This amplifier sounds great and will be with me for years to come. 

 

Thanks for looking at the TW Labs HFA-01!
Tumbleweed