I have a radio very similar to the one listed here:http://www.ebay.com/itm/King-Hinners-Si ... 2569e81f28
I noticed that when I plug the speaker into the terminal on the left, the radio runs on all 5 tubes, but it only runs of 4 tubes when it is plugged into the middle. When I plug it in all the way on the right, only three tubes light up. What is the purpose of the 3 audio terminals? Is my radio operating correctly?