AKSA Amp

11/7/01

This page describes my Aspen Kitset Amplifier (AKSA). It has two incarnations--an earlier 55W version and a newer 100W version. Both power amps utilize a dual mono configuration, where each amplifier is a self-contained unit (power transformer, power supply, amp). The AKSA was designed and is marketed by Printed Electronics in Australia. I decided to add functionality by putting in my own volume control, a 20Kohm DACT CT-2 stepped attenuator. The Elma rotary switch feels precise and deliberate in its motion. Sweet.

Here is a picture of the finished product. 

OK, so the volume control is a little off center. My father drilled it. HAHAHA. He drilled it, but it was a combination of hurrying to finish the amp up at around 10pm, me marking the center off by around 1mm, then my father starting the drill bit 1 mm further away from the center mark. At least it works.

I chose the AKSA due to its good reputation. I figured that the 100W version would be more suitable for my needs as I will soon upgrade to lower efficiency speakers (86dB / 1W 1m) For those considering to build the amp, let me tell you a little about myself. I had limited experience with soldering prior to this project. Soldering was required in a physics course I took at college, so even though I didn't have to make millions of solder joints, I am decently handy with the soldering iron. That class was fun, or at least the experimentation was pretty fun. I know the basics of E&M and some stuff about RLC. I forgot most of the stuff about L. I remember more about R and C. I know a little about mains wiring, but mostly I had my father help me with that part to make sure that I wasn't going to kill myself. I know how to follow directions. That is probably the most critical skill required in kitset building, along with concentration and excellent eyesight.

Building your own amp is like knowing what's in sausage. You know every little imperfection, and you worry about the things that you've done (like, did I heat that semiconductor too much?). It is definitely not for the faint of heart. However, it is a very rewarding experience, knowing that you built the dang thing yourself. 

The AKSA is pretty much finished. I will maybe tweak around with shielding of the input signal, and with the chassis wires. There is a little hum at the speakers, even though I am using low-ish efficiency speakers (88dB / 1W 1m).  The amplifier needs some burn-in time, but it has very dynamic, highly resolved, uncolored sound.  

Here are a few pictures of the building process. There unfortunately isn't much detail here. Here is a picture of the amplifier chassis, heatsinks and dual transformers.

Here is a picture towards the end of the project. The transformers were mounted, and the various jacks (speaker, RCA, power) and power switch were also mounted. The chassis feet have also been mounted. The power jack is a little skewed in its mounting. I might fix it in the future. I am kind of peeved, but I am also glad it is in the back panel. Here is a picture, viewed from the backside:

I mounted the PCBs to the side panel/heatsink assembly. As you can see, the screw holes that mount the heatsink to the side panel were drilled pretty much ad hoc. However, they line up pretty well! I used a drill press for this step.

The supplied power supply PCB was made for 30mm caps or less. Unfortunately the capacitors I have, Nichicon KG Gold Tune - Great Supply IV, are slightly above this measurement, even though they are specified as 30mm nominal. Isn't that the way of it? I tried to modify the PCB, but it became too crowded. I had to fabricate my own PCB.

Upgrades that I may consider in the future are better internal wiring, better RCA connectors, maybe some shielding of the AC cords leading into the power supply.

Many thanks to General Semiconductor for sending free samples of their UG10DCT rectifier. You would not believe how hard it is to find this particular rectifier in North America.