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)