Greetings Sunn Fans!
I have a technical question regarding the feedback circuit for my Sunn Studio PA head. The original output transformer secondary had a single winding with taps for 4, 8 and 16 ohms with the speaker jacks wired to the 4 and 8 ohm taps with switching jacks to use the 8 ohm tap with one speaker and the 4 ohm tap with two speakers (two 8 ohm speakers in parallel). The feedback network was wired to the 16 ohm tap. The output transformer was blown so I installed a Hammond 1650N. The secondary of the new Hammond transformer has two windings, one at 4 ohms and the other at 8 ohms with a 4 ohm tap. Hammond provides three schematics that allow you to connect the secondary leads in different configurations to provide either a 4, 8 or 16 ohm output, however you must pick just one because of the two separate secondary windings. I've wired the transformer for 4 ohms and the two output jacks in parallel (eliminating the switching function) so that I have an impedance match with two 8 ohm speaker cabinets (the original Sunn Studio PA cabs). There is an impedance mis-match if a single 8 ohm cab is used, but better to have a higher impedance than lower. So, my question is.......is there a way to connect the existing feedback network to the new transformer when I don't have a 16 ohm tap? Change some of the resistor values in the feedback network?
I know I could wire the secondary at 16 ohms with the output jacks in series for two 8 ohm cabs. But if one cab is used I'd have a lower impedance mis-match, working the output tubes and transformer much harder. Thoughts???
Thanks for your help!
Ryan
