GAS Thoebe preamp: Stereo push buttons?

I just picked up this preamp.
It has 2 stereo push buttons marked stereo A and stereo B

The preamp refers to the left and right channel as A and B.

I am at a loss as to what these buttons do. When both are
pressed it sounds like the system is in mono mode.

anyone out there have a manual ?

craig in ottawa.
If I remember right, Stereo A feeds that channel to both sides in mono mode and Stereo B the other channel. I am not 100% sure, it is now more than 25 years ago, that I tried one. But its easy to find out: Just unplug the input to your left or right channels, play music and see what happens. Either A or B should be dead, the other one should play in mono mode from both of your speakers.
Cheers and happy listening!
What Detlof said is right.
I have another problem with my Thoebe. When playing music with the mute button pressed and volume at minium position, I can hear high freqency comes out ( at around -30dB with music signal > 3kHz ). However, when I release the mute button with volume at minium, only very low music coming out ( -40dB ).
Does any one who owned this preamp have the same phenomenon?


It has been several years since I replaced my Thoebe preamp, but I recall that it had the same phenomenon with the mute button when the volume control was set at minimum: signal level at the preamp outputs would be louder with the mute engaged than with it disengaged.

I have the manual at home, if you want to contact me at