Ohm Problem

L

lester

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?
 
L

lester

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

Member
Messages
13,040
[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.
 
L

lester

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.
 
L

lester

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
Lester
 




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