Tone generator and Audio millivoltmeter

Rörvoltmeter = Vacuum Tube Voltmeter Sinusvågsgenerator = Sine Wave Generator

This was made from two different articles but I decided to build them into one cabinet. It is now more than 40 years since I put it together.

The Decade Tone Generator designed by my friend Jon Idestam-Almquist. From an article in "Radio & Television" April, 1965.

The Vacuum Tube Voltmeter, also designed by Jon Idestam-Almquist From an article in "Radio & Television" March, 1963.

The voltmeters original appearance...

...and its interior.

Inside my version...

...close-up of the switches with components for frequency selection.

The voltmeter part...

Bottom view with all nice old resistors and capacitors.

The THD is just below 0,1 % (< -60 dB)