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i own a marshall 5212 split channel 50 solid state combo(along with jcm 900 sl-x 50wt stack). what i was wondering is this. the amp is designed to run on 4ohm load. is there a mod that can be done to select the ohmage? i would like to be able to run stock spkrs and 4x12 or two 4x12 and stock(maybe)? right now i run out of the combo from effect send into some pedals and into the sl-x effect return. sounds great at indoor levels. but if i could modify the combo to be able to run on 4,8,16 ohms would rule!
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If the power amp is solid state, it doesn't care what impedance is hooked up to it as long as it is no lower than the rated impedance (i.e., you can't run it with a 2 Ohm load). You will do absolutely no harm to the amp running it on 8 or 16 Ohms. However, you will get reduced power running with higher loads. 1/2 the power for every doubling of the load. So with an 8Ohm cabinet you will only deliver about 25 watts to the speakers. Half power doesn't mean half as loud, you will probably not even notice the volume drop.
A solid state power amp is a constant VOLTAGE device, tube power amps are constant CURRENT devices. So, the solid state amp will deliver the same voltage to the speakers regardless if it is a 4, 8 or 16 Ohm load. Ohm's law will tell you the power delivered to each speaker load (V squared / R).
So, just plug in the 8 or 16 ohm load & have at it. No mods needed. -
oh so cool! i didnt know that. kind of figured as much but its been so long since ive just experimented and it dont pay to play around with vintage equipment and ruin it. thanx so much for your help. now if i can get my echoplex problem solveld(check the effect portion of the forum) ill be a happier camper.Comment
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