#4
Beitrag
von braunfreund » 29.05.2013, 20:50
Hi Woytek,
the SK61 is equipped with two different amplifiers: one for full range band (bass/mid/high with EL84 output tube and one only for mid and high range with the smaller EL95 output tube.
By connecting a second loudspeaker to the other channel, stereo reproduction could be made. The bass frequencies were transmitted only over one channel since it was claimed that they cannot be located in the room (similar to today's subwoofer/ 2x mid/ high speaker systems). A curious solution from the early days of stereo.
The switch at the back is named "Seitenwahl", that means "side selector". Depending on how the SK61 is placed at the left or right side of the room (and the additional speaker , of course, at the other side), it could be selected by the switch which of both speakers gets the fullrange signal. But, as a side effect, the two channels from the record player can also be reversed, that means the record's right channel comes out of the left speaker.
The (first stereo) model before, SK6, has two EL95 output tubes, but the remaining components around are made so that also only one channel transmits the fullrange sound. I have tried to modify the other channel so that it also transmits fullrange (changing some capacitors and inserting the bigger output transformer from an SK5). But this would not work well, the amplifiers then tended to oscillations and, for whatever reason, did not sound equal. So this was not the right solution.
In the SK61, Braun brought back the EL84 output stage to get the more powerful sound (4 watts) as at the older mono versions. The second channel was reduced to an "auxiliary" channel with only 2 watts.
So, you would not get equal fullrange transmission on both channels as with a "real" stereo system. The excursion to stereophony was not successful, and the following version SK55 was a mono system again similar to the old SK5.
Best regards,
Lutz
