I've got a beautiful JMP 2203 top from 1979, and I'm now waiting for my brand new 1960AHW cabinet to arrive. The problem is that the cab is 16 ohms, and it's only possible to select 4 or 8 ohms output on the switch on the back of my amp. The switch actually have 5 possible positions, but only 4 and 8 ohms are printed on the switch. It also has got a seperate label on the back that specifies 4 or 8 ohms.
I read somewhere that the Canadian amps didn't have 16 ohm output because of some Canadian rules, but my amp is originally sold in Scandinavia (Sweden), as one can see on the label on the back of the amp. Is there a "hidden" 16 ohm posibillity when I set the switch to the position after 8 ohm? Will I have to rewire my new cab to 4 ohms before I can use it? Any help will be much apreciated...
? manual says usually marked 4,8,16 ohm if not labeled call marshall to verify situtaion . they r very helpful . us east coast time they are open 4am to noon . i would definfinety just contact them before wasted time and money +44(0)1908 375411. yoor one cabinet should be pluged into a 16 as u suggest . if u had 2 16 ohm cabs into 8ohm speaker outputs it wuld be correct in tube amp . good luck .
From a solid state and electronics perspective, running a 16 ohm load (speaker) from a 4 to 8 ohm head unit is only going to limit the volume or power you can output. Generally speaking, you only run into trouble when you run a load (speaker) that is lower than what the head unit is rated for.
I.e. you would get into trouble running a 4 ohm load (speader) from an 8 or 16 ohm head unit.
Now tube amplifiers should be the same, but I do not have nearly as much experience with tube electronics as I do solid state.
Thanks for your reply. As I understand it mismatching impedance on a tube amp is far more critical than on a solid state amp. I've read that a mismatch one step up (8 ohm cab on a 4 ohm amp output or 16 ohm cab on a 8 ohm amp output) should be safe, but that was especially concerning Mesa amps. Please correct me if I'm wrong, but from what I've read Marshall's are more fragile when it comes to mismatching.
I'm looking into the option of modifying my amp so it can handle a 16 ohm load. If that's not possible I guess I'll have to rewire the cab...
Although I have 20+ yrs experience as an electronics engineer, I cannot accurate say how the Marshall amp will respond. My advice here unfortunately is fairly general in these regards. Best if one of the Marshall engineers can respond to your mismatching question.
Best of luck. Cheers!
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