Use speakers on a Marshall JVM for Marshall head?

darrenw5094

I have a Marshall JVM 410 combo at home. It has 2 12" Celestions. One Vintage and one Heritage. Would it be possible to connect a different Marshall head to the speakers on the JVM combo instead of buying another 2X12 cab? I would not be using the JVM combo pre amp or power amp.

spoonbadger

Yup!.That should be fine. As long as the impedances match (or can be made to match) between the new head and the old speakers. This shouldn't be a problem though,as the vast majority of heads have variable impedance selectors, and you'll almost certainly be able to configure the two speakers into 4, 8 or 16 ohms. Might need a longer speaker cable though .

Btw, JVM400, is that one of the sparkly new marshalls with the small army of knobs?.

Edit: Do not just plug the speakers into the new head unless you understand speaker impedances, or without talking to someone who does, or asking us even.

darrenw5094

spoonbadger wrote: »

Yup!.That should be fine. As long as the impedances match (or can be made to match) between the new head and the old speakers. This shouldn't be a problem though,as the vast majority of heads have variable impedance selectors, and you'll almost certainly be able to configure the two speakers into 4, 8 or 16 ohms. Might need a longer speaker cable though .

Btw, JVM400, is that one of the sparkly new marshalls with the small army of knobs?.

Yup......it's the Marshall JVM410c monster........more knobs than the UK.
There are 5 inputs for speakers. One is the lead going into the 1 x 16 Ohm input.
What would happen if i made a mistake and wrong Ohm input was used ??

Welease

darrenw5094 wrote: »

What would happen if i made a mistake and wrong Ohm input was used ??

You could blow the amp.. so be careful..

Bascially (and check this first out to confirm)

Perfect scenario is plugging a 16 Ohm amp into a 16 Ohm cab (or 8 into 8, 4 into 4).
Workable is a lower Ohm amp into a higher Ohm cab (but it will lower the output volume) i.e. 100w 8 Ohm amp into 16 Ohm cab will give 50w of power
DO NOT put a higher Ohm amp into a lower Ohm cab.. i.e. 16 Ohm amp into 4 Ohm cab.. it won't take enough load off the amp, and will damage it..

But please get what I have said confirmed first before doing anything

darrenw5094

I will have to post up 2 photos tomorrow to be sure as to what i am doing.

The Ohm thang always gets me.

Eoin Madsen

darrenw5094 wrote: »

What would happen if i made a mistake and wrong Ohm input was used ??

Worst-case scenario, throwing power into a miss-match could kill the output transformer (if valve amp) or the power transistors (if solidstate). But more likely, it will work okay and you'll just lose some power and some frequency response while running it incorrectly.

Eoin Madsen

Welease's point is only re: valve amps, btw. Solidstate powerstages are basically the opposite.

I caused a (homemade, I think) solidstate amp to go on fire once (I was moving the speaker and the crappy - also homemade - speaker cable was intermittent). The smoke was kinda blue, and the smell lingered in the venue for weeks. :pac:

Paolo_M

Most valve amps are fairly tolerant of mis-matches up 100%. As the lads said; mis-matches beyond that (eg 16 ohm head into 4 ohm cab) can and do damage to OTs as well as valves.

SS amps handle mis-match very well and can generally tolerate no load quite well. Most SS amps you see have power rating given @ 4, 8 and 16 ohms.
However they absolutley cannot tolerate a shorted output.
SS pretty much tries to deliver what power you ask for. No load is asking for no power, a short is asking for infinite power so they generally go on fire trying to deliver it!!