The variable EQ preamplifier for reproduction of 78rpm shellac and also vinyl mono records is finished.
I also just got my new Scheu turntable set up with a mono cartridge and 78rpm platter speed to test it.
The preamp has separate controls for Bass Turnover frequency and Treble Roll Off as described in part 2.
The inside of the preamp:
The different EQ networks sit on the right side right behind the faceplate. Signal tubes in the middle and power supply in the back.
I am now enjoying some beautiful 78rpm records. The mono cartridge is brand new and still needs some break in, but the sound from those Shellack discs is already amazing.
I will go more into details about the entire 78 rpm setup in part 4 after adjustment of the turntable and break in of the new cartridge are complete. Some of the EQ settings also need some fine adjustment.