the load on the Captor is the same as the Torpedo Live. The one in the Torpedo is different because it is a switchable 4/8/16 Ohms load.
if your amp only has a 4 Ohms output it's always best to try and match that with the cabinet/load. It's usually no big deal to use a 8 Ohms load on a 4 Ohms output, but it may change the way the amp works and sounds.
Comparing what we do to other loadboxes on the market, well, I'd say the principle is pretty much always the same, we just try to design them so they do not tint the amp character too much, and we count on the digital simulation to take care of that aspect. Some people will find them transparent and it's cool, other will find them transparent and it's bad. ^^
Another aspect which is pretty much never discussed, is that we implemented since day one a security system that will protect both the torpedo and the amp in case of overheating. That should help you try to push the system to the limits without worrying about taking too much risk. This being said, remember that most (recent) amps are not really designed to run full blast for too long.
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