Ohms & solid state(hybrid) heads

[Rich#6]

I have a marshall vs100, a marshall 1966B 2x12 8ohms and a line 6 that is 4x12 and says mono 4ohms(has 2 plugs and says 8ohms if both used). If I use both cabinets will it damage the head? I know if I use 2 different ohms cabinets with a tube head it will fry it correct?

[DonP]

With most SS amps, the less ohms in the speaker load, the less resistance to power and the more power that will flow. In order to know what the VS100 can handle, I'd need to know what is is rated for.

For example, with the Marshall Micro Stacks they use 2 x 16 ohm cabs = 8 ohms to the amp. I have another set of cabs with V10 speakers that are 2 x 8 ohms = 4ohms to the amp. The Micro Stack has a note on the back that a 2 ohm load may damage it, so I would not use 2 4 ohm cabs.

It doesn't matter if you use a mixture of cabinets with different ohms, what matters is are you giving the amp enough ohms to keep it from running away and burning itself up.

If you don't know how to calculate the ohms from the speaker cabs, connect the tips of the cabs together, connect the shields of the cabs together, then get an ohm reading from the tip to the shield with a DMM.

[Rich#6]

the min. on the vs100 is 4 ohms. so I have an 8 and a 4 would that be 6ohms?

[Hellbat]

It depends how the cabinets are wired. In series the load would be 12 ohms. In parallel it would be 2.67 ohms.

[Rich#6]

It depends how the cabinets are wired. In series the load would be 12 ohms. In parallel it would be 2.67 ohms.

How do I find that out?

[Hellbat]

Well, there's the part of the formula that I'm not sure about hehe...

I would see if it's indicated on the cabinet labeling as to whether that pass through connection is wired series or parallel. Or if it's documented on the manufacturer website.

[MetalMedal II]

It depends how the cabinets are wired. In series the load would be 12 ohms. In parallel it would be 2.67 ohms.

If u have 2 outputs on the amp and hook them both to the mono cabs, I'm pretty sure that will be 2.6 ohm and you'll fry the amp, regardless if it's tube or SS. U can always go into a higher ohm speaker rating but going to a lower will be trouble.

[DonP]

I think I remember the formula for caculating parallel ohms being (R1 * R2 * R3....) / (R1 + R2 + R3....) so for the example above (8 * 4) / (8 + 4) = 2.66666667

[Franx]

You could rewire the Line6 cab for 16 ohms mono. Use something like the Marshall socket plate, so you can switch to 4 ohms if you need them;
connected parallel with the 8 ohm 1966B cab you will get ~ 5,3 ohms. Almost perfect for the VS100 !