'73 marshall ohm

Hey i have a 1973 marshall 100w superlead and i was wondering how many ohms it uses.. cause i have an 8 ohm cab i made over the summer and i thought itd be nice to have the fullstack going, but the amp doesnt say anywhere on it how many ohms, niether does the real cab which is a 73 1960b cab. i was wondering if anyone knew

...just hook it up.

An easy way to think of it is a 4ohm speaker will double the wattage on your amp, but it works the amp harder. Generally an 8ohm speaker will work on just about anything. It's only when you start getting into 2ohm speakers that you have to worry about your amp being stable enough to handle it.

Originally Posted by: schmangeAn easy way to think of it is a 4ohm speaker will double the wattage on your amp, but it works the amp harder. Generally an 8ohm speaker will work on just about anything. It's only when you start getting into 2ohm speakers that you have to worry about your amp being stable enough to handle it.

[font=trebuchet ms]NOOOOOOooooooo! :eek:

Tube amps destroy themselves when the load impedance doesn't match the output impedance! That's why they have output matching transformers.

You can get a ballpark estimate of your 1960b cab by plugging a cable into it and measuring the other end of the cable with an Ohm-meter. This DC resistance value will be a bit lower than the AC impedance, but it should be useful. An 8 Ohm cab will measure about 5 - 6 Ohms on a meter. A 16 Ohm cab will be double that much: about 10 - 12 Ohms. A 4 Ohm cab will measure something like 3 Ohms.

You can also post at the Plexi Palace forum where there are likely to be several people with the same rig as yours.[/font]

I guess it doesn't work the same way for guitar amps as it does for home audio eh?
I can run down to 2ohm speakers on my Luxman with no problem.
Actually, I can put a pencil lead between the speaker leads and all it does is get red hot.

[font=trebuchet ms]Is your Luxman tube or transistor? Transistor amps only get unhappy if the load impedance is too low. Impedance mismatches (either high or low) on a tube output stage cause much higher losses in the tubes and the transformer. That translates into heat. That pencil lead may not be the only thing getting hot.[/font]

so it sounds like im going to radioshack?
yeah i hooked up my 8ohm to my crate15w 4 ohm and it sorta crapped out.. it would work fine for like 10 minutes then the volume would reduce and it suck

I own an older marshall and some of the older 1960 cabs are 16ohm BUT use caution because in a band setting too much is too much onstage volume
the old ones sound great with a power brake and a two twelve cab with a ribbon mic rock on....jeff :cool: