Multi-tap transformers & speaker loads

I’ve been asked this question several times in as many days so it seems like a good time to discuss the question.  I’ve previously mentioned how the proper speaker load is important as well as matched speaker impedances in a multiple speaker configuration, so we don’t need to cover that again.  This is directed towards amps that have individual speaker output jacks for their various speaker impedance options.  There are more transformers being offered now with two or three different impedance options, and for this discussion we’ll use the 5E3 D-Lux for an example as I do carry some tweed Deluxe output transformers with 4/8/16 ohm output taps. Although there is room for all three output jacks on the chassis I’m usually just asked for the 4 & 8 ohm taps. So the basic question that’s asked is if I have both a 4 ohm & an 8 ohm output jack, can I plug a 4 ohm speaker into the 4 ohm output & then also plug an 8 ohm speaker into the 8 ohm output.

The simple answer is that it’s not recommended as it places an odd load on the output transformer.  Once again, the 4 ohm speaker offers the least resistance so that’s where the majority of the signal will be going as well.  So between the unusual strain it places on the output transformer and the fact that you probably wouldn’t be happy with the result anyway, it’s better to stay within the design limits of the output transformer.

The 4 ohm output would be used if you had a 4 ohm speaker load like a favorite speaker that you can’t live without but it’s a 4 ohm unit.  Another scenario would be an 8 ohm internal speaker & an 8 ohm extension cab, and then you’d want to use a 1/4″ female speaker jack wired off the internal speaker.  If you were just using an 8 ohm internal speaker then you’d want to plug into the 8 ohm output.

2 thoughts on “Multi-tap transformers & speaker loads

  1. I am currently using a 16ohm 412 cab that can be set to 8ohms and run in stereo. If I bought one of your Mutt amps and wanted the higher wattage transformer, how would I run it off of that cabinet? I am fond of the cab. It is a Peavey with a metal grill in the front with 4 12″ Sheffield speakers. I got the cabinet cheap and for some reason, those speakers sound great. I am not in a position to repurchase all new speakers yet, and I don’t want to rewire the cabinet. What would you be able to do with that information?


    • Hi TJ,
      That’s a good question, and one that a lot of us have asked at one time or another. I agree that buying new speakers would be expensive, and then the cab may not be the right impedance for other amps that you want to use as well. Re-wiring the speakers could be an option but once again it may limit your ability to use the cab with other amps that you my want to use. So the simple solution in a case like yours would be a multi-tap output transformer that lets you choose between 4/8/16 ohm outputs. On some amps you may have the room to add an impedance selector switch while on others you may only have space for one or two output jacks wired to specific impedances. The multi-tap output transformers do cost a bit more than a single impedance unit, but they allow you to use a variety of cabinets so it can be a good investment.

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