Name:    Glenn Smith
Email:   smitty@smithga.com  
Subject: speaker wiring question
Thread:  246
Time:    Wed, 7 Nov 2001 11:44:43 UTC

Howdy,


I read all the earlier posts on this topic. It got me curious as when I purchased my amp the switch was in the 8 ohm position (which should only apply when an extension cab is used).


A little thinking produced the only logic that the 2 12" speakers are 8 ohm each, wired in parallel for 4 ohms. If you add an extension cab wired the same, you get 8 ohms (thus the notice on the plate saying the jacks are wired in series). It all made sense.


Except . . . (there is always one of those). Except, my switch was in the 8 ohm position. Now there is no way this amp has been running for 20 years in the wrong setting. Or is there?


I whipped out the meter and started tracing wires. What had happened is some previous owner of my 212-75 had changed the speakers from being wired in parallel to being wired in series. From the aging on the insulation, I would estimate it was done many, many years ago.


Only the speakers were changed. The jacks are still wired in series and the transformer looks to be original. Thus, this modification has made it so the amp is actually running a 16 ohm load at all times and adding a speaker extension is out of the question (unless increasing the load imbalance is a good thing).


Now the question: What would the benefits be of changing this wiring? I've kicked this around in my head for a while and just can't make it add up. By the way, the workmanship is clean, this wasn't the work of some hack.


Any thoughts?


Take care,


Glenn