The Telefunken Echomixer is a interesting German mono mixer from the year 1961. A great vintage piece with old discrete comoponents (old transistors, no tubes). It is a Mixer + an amazing spring reverberator. the first A channel is dry, and on B and C you can select the spring reverb amount between the two lower sliders.
Overdriving the input sounds also nice. I did this with a Roland TR-606. In the video I also play a Korg MS-20 through the Echomixer.
The Echomixer has only DIN jacks (they look like MIDI jacks).
It was used by Klaus Schulze.