Saturday, July 14, 2007

Preamp for Wind Harp

I built a preamp circuit for use with the wind harp. The amplifier uses a J-fet transistor to connect to a magnetic pickup without loading down the pickup too much. The rest of the circuit brings up the gain enough to drive a set of Amplified PC Speakers.

Bread boarded circuit while in the design phase. That mess really works!

The preamp can also be plugged into the microphone input on a PC. Dual coil design is next to test out as a method to buck out hum. Right now, I'm just using a single coil with a magnet as the pickup. The circuit is still a "work in progress" and has not been finalized. I will post the final tweeks when done.

You can download a pdf of the schematic HERE

I also made a Youtube video of the waveform. View it HERE
The video shows a predominate frequency at about 440 hz and low frequency ripple from hum and vibration of the mount. When a truck drives by it will increase. More work on the preamp can be done to remove this.

You can listen to the harp "Live", if I have Windows Media Encoder on. Just open Windows Media Player, click "File","URL" then copy and paste this URL:

I used a freeware oscilloscope/FFT program to view the signal. Get it HERE

The author of Watson's eBlog has been very helpful in my design of the preamp. He also has an excellent design of a preamp of his own for bringing the sounds of the outdoors inside. The site can be found HERE

No comments: