Peter Redmer, of Caffeinated Pixels, is one happy little wirehead. For Christmas this year, his dad, an electrical engineer, built him a tube amp and a set of speakers for his iPod. Here’s dad on the specs:
Amplifier: In order to keep the design small, I am using a hybrid design for the amplifier. A push-pull driver using a OP275 dual opamp is used to drive a pair of 5902 output tubes for each channel. A small amount of negative feedback is employed to control distortion and level the frequency response. The amplifier produces about 1.25 watts per channel. The overall gain of the amplifier is set to be used with the output from a portable MP3 player. The volume control on the MP3 player is used to set the output level.
Speakers: The system also needed a pair of small speakers to go along with the amplifier. A two inch full range driver was available from HiVi. I put the numbers into BassBox Pro and worked out a design. I ended up with a ported box of about .035cubic feet in size. The speakers have a low frequency point of about 120HZ. They sound much better than most desktop computer setups. A subwoofer would be a great addition, but that’s a project for another day!
One cannot underestimate the value of a thoughtfully handmade gift like this, whether hi-tech or low. My wife had a dulcimer that her father made for her one year when she was a teen. She cherished that thing more than just about any other possession. You can tell how thrilled Peter is by his father’s gift.
One of these days, I swear I’m going to break down and build a tube amp like this myself. Has anyone here built a small amp like this for portable audio?