mark iv extensions

[fatoni]

can you run one cab via the 4 ohm output and another via 8 ohm, or is the 8 ohm just for mono?

 

[jerseydrew]

tell us what ohms your cabs are first.

 

[fatoni]

4 and 8

 

[MrMarkIII]

Any/all of those speaker outputs are mono. Any way you can re-wire the 4 ohm cab, or run the cabs in series? Running a 4 and 8 ohm cab in parallel is gonna get down to 2.6 ohms, a bit low. Not fatal, perhaps, but your power tubes will wear out faster.

 

[MrMarkIII]

Any/all of those speaker outputs are mono. Any way you can re-wire the 4 ohm cab, or run the cabs in series? Running a 4 and 8 ohm cab in parallel is gonna get down to 2.6 ohms, a bit low. Not fatal, perhaps, but your power tubes will wear out faster.

 

[fatoni]

if they are all mono why do they give you two 4 ohm outputs?

 

[mrd]

For running two 8 ohm cabs together.

When you run your cabs in parallel, there's a little formula for figuring out the total load on the amp. Take all the cabs you're using, multiply their ohm ratings and divide that number by the ohm ratings added together.

You have 8 and 4.

8 x 4 = 32 for the first number
8 + 4 = 12

32 divided by 12 is 2.6666... which is what MrMarkIII got.

The two 4 ohm taps are for running two 8 ohm cabs together.

8 x 8 = 64
8 + 8 = 16

64 over 16 = 4, IE: the amp expects a 4 ohm load.