Hi there!! I was wondering how i could send a 40hz signal to my svt-vr without an oscilloscope, and how to check the output signal with my multi-meter. http://ampeg.com/pdf/SVTVR.pdf And by the way: I just got NOS General electric 12AX7 for my preamp. Do you think it is necessary to put such good tubes in the driver section? Thx for you help guys!!!