ilarranaga
New Member
- Joined
- May 17, 2011
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Hi guys,
I bought a JCM900 (4100) amp and a JCM900-1960A cab both together and both used (secondhand) 2 years ago. The man who sold me the amp and the cab told me to use "from this jack in the amp to this jack in the cab with the switches like this". He was doing it in that way for around 10 years. I did not think more about it and just followed his instructions.
I never understood why I should plug the cable in this way so I decided to learn about it. To do that I read the thread "Marshall Amp Forum > The Amps > Marshall Amps > Speaker Load on a JCM900 4100 Hi-Gain".
Well, here starts the question.
I realized that I was using the 4 ohms input in the cab with the switch in mono. I realized that I had the switch in the amp in (4) 16 ohms and that this actually should be 16 ohms since my amp is a head. This is what I understood in the thread that I had mentioned.
So... mismatch!! Very bad!! I am using the 16 ohms output in my amp to a 4 ohms input in my cab. But they are working in this way around 12 years and the amp is still there, it works.
This fact made me to think that perharps the amps was modified to offer a 4 ohms output changing the cables on the OT as is showed in the thread I mentioned. But NO!! It seems to be configured as a 16 ohms output.
Maybe the cab was re-cabled and the 4ohms input was working as 16ohms... NEITHER!! I measured the impedance with a multimeter and is around 4 ohms (around 5,5 ohms to be more accurate, but the multimeter is not the best...).
I am really concerned about this problem...
Am I really using a wrong 16ohms-4ohms configuration?
If that is the case, why is the amp still alive after 12 years?
Can I measure with a polimeter or is it any way to know for sure if my amp is offering a 16 ohms or a 4 ohms output?
Thanks a lot!
I bought a JCM900 (4100) amp and a JCM900-1960A cab both together and both used (secondhand) 2 years ago. The man who sold me the amp and the cab told me to use "from this jack in the amp to this jack in the cab with the switches like this". He was doing it in that way for around 10 years. I did not think more about it and just followed his instructions.
I never understood why I should plug the cable in this way so I decided to learn about it. To do that I read the thread "Marshall Amp Forum > The Amps > Marshall Amps > Speaker Load on a JCM900 4100 Hi-Gain".
Well, here starts the question.
I realized that I was using the 4 ohms input in the cab with the switch in mono. I realized that I had the switch in the amp in (4) 16 ohms and that this actually should be 16 ohms since my amp is a head. This is what I understood in the thread that I had mentioned.
So... mismatch!! Very bad!! I am using the 16 ohms output in my amp to a 4 ohms input in my cab. But they are working in this way around 12 years and the amp is still there, it works.
This fact made me to think that perharps the amps was modified to offer a 4 ohms output changing the cables on the OT as is showed in the thread I mentioned. But NO!! It seems to be configured as a 16 ohms output.
Maybe the cab was re-cabled and the 4ohms input was working as 16ohms... NEITHER!! I measured the impedance with a multimeter and is around 4 ohms (around 5,5 ohms to be more accurate, but the multimeter is not the best...).
I am really concerned about this problem...
Am I really using a wrong 16ohms-4ohms configuration?
If that is the case, why is the amp still alive after 12 years?
Can I measure with a polimeter or is it any way to know for sure if my amp is offering a 16 ohms or a 4 ohms output?
Thanks a lot!