Monthly Archives: December 2014

Transconductance Preamp v2

My First Preamp has proofed its quality now for over a year. As I now plan to upgrade my record player with an integrated one, I worked on a improved and simplified version of my first prototype.

I already had the idea for this when my first version wasn’t even built, but I needed some time for basic design evaluation and performance simulation.

The most important change was to get rid of the bipolar supply voltage and a fast self-biasing upon startup while maintaining a low cutoff frequency. Waiting for more than 30 seconds until it gets operational while generating a loud “Plob” was not okay. Luckily I had an brilliant idea how to bypass this problem.

Of course it will again have an High-Z Current output that must be terminated with the proper 620 Ohms.

Here is the simplified schematic for Version 2 of my Transconductance Preamp:

Preamp Unipolar

Over the Xmas holidays I had enough time to solder the new prototype, it fits nicely into a corner of my Pioneer Record Player: