This project is going to take a while since I’m slammed in the shop, but I’m in the process of converting a Bose® 901 Series I Active Equalizer to  a test platform. With sockets for the transistors, and clip connections for the important capacitors, this platform will let me experiment more easily with various different upgrade choices to see which offer the best performance.

Unfortunately, there’s no strict “before” measurement since the vintage caps are dead and this unit isn’t producing any output right now (the overwhelming case on Series I equalizers), but I’ll take some good measurements with the bare minimum components needed to do a successful test as the baseline and see where it goes from there.

Should be interesting!