The speaker output of a tube amp is designed to be matched to one (or several) specific load(s). An 8 ohms speaker output is supposed to be connected to an 8 ohms speaker or load box. In some situations, however, you may not be able to match the impedance of the load to the impedance of the speaker output – for example – if you have a 8 ohms speaker or load box and an amp with only a 16 ohms output. Connecting the two leads to an impedance mismatch.

This mismatch may or may not be a problem, it actually heavily depends on the amp’s design, and the way you use it. It is generally accepted that a small mismatch is not a problem if you play the amp at a low level, but this isn’t a general rule. As a result, we can’t guarantee that a mismatch will always work for you. It’s always best to go for the right impedance if possible.

That being said, if you want or need to mismatch the impedance of the amp and load, we recommend the following:

  • Only go for small mismatches – the “one step away” rule: 2 vs 4, 4 vs 8, 8 vs 16. But not 2 vs 8 or 16, 4 vs 16.

  • Play your amp at a low level, at least at first. Monitor the behavior of the amp, the tone coming out of it, the color of the output tubes. If anything seems wrong, stop playing. In short, follow even more carefully the Recommendation on the proper use of a loadbox with a tube amplifier you’ll find in the user manual of your Torpedo product (here, for example, for the Torpedo Captor).

  • On a related topic, read here about what a low level might be for your amp.

Transistor amps are designed differently, and usually have a “minimum load” rating rather than expecting an exact impedance match. This means you can use any speaker or load box with an impedance equal or greater than this rating. A speaker output rated “8 ohms min” can safely be used with 8 or 16 ohms loads.

4 thoughts on “Mismatching the impedance of your amp and load box?

  1. Ben Robinson says:

    I assume it does not matter what impedance the speaker cab is? i.e. provided the amp and Captor X match impedance – i.e. 16ohm amp output into 16ohm Captor X – I can add a 8ohm speaker cab to the Captor X if I choose? I have an 8ohm cab and one of my amps is 16ohm only output, and I currently use a Mass Weber set to 16ohm to bridge this difference.

    • Jason Wilding says:

      The impedance of the cabinet does not matter if the attenuator is engaged (Volume Level on LOW or halfway position). If the Volume Level switch is on FULL, the cabinet’s impedance is the impedance taken into account.

  2. Eliah says:

    I’m owner of the Marshall JCM410C 100W and I wish to use one of the Two notes Captor; honestly I borrowed version of 4 Ohm and now I don’t know is is allowed to connect it between head speaker output and build-in speakers? If yes, how to solve it and enjoy cranked JVM at bedroom atmosphere? Thanks.

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