Ohm Problem



Hi there, I have a 100W Marshall 67' Major head, and I am into getting a 2X12 cab today, now I have an option of getting a cab of two original Greenbacks, thou the cab impendence is 16Ohm, and the output resistance of the head is 8Ohm. If I connect them both, would it do any harm to each?


Thanks a lot, though mine is set on 100W (the 200W is while using Kt88 I believe). It does have the 4/8/16 selector, though I think you have to solder it from the inside, and yet I am not to much capable with these stuff

Thanks again

John Phillips

[Lara Croft]

Ah hahhh...

[/Lara Croft]


... so you're running it on EL34s?

And it's hard-wired for 8 ohms...

And you wan to run a 16-ohm 50W cabinet...

So there is a very easy solution: pull two of the power tubes (inner pair or outer pair). This will immediately give you the correct impedance match and a maximum power output around 50W. You don't need to rebias either, assuming it's correctly set at the moment. I'd still be a bit careful, since it still may peak above that with those huge transformers basically running near idle, but it will at least be safe to play it at a fair volume.


Thank you so much, you have really been a great help to my problem, this place makes it way more fun dealing with equipment!

Thanks again.


Alright, so I've pulled out two of the EL34 power tubes, but does it matter which ones I've pulled? Also, I someone here has got this amp, do you know what does the black circle on the back panal is usefull for (the one with the 4/8/16 Ohm) ?

And last thing, John, I would be really glad if you could tell me how pulling out two power tubes affects on the impendence, well I understend it drops the output W to half, but, why would it risen up the impendence?

Thanks a lot again

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