Marshall head rated at 4ohms

[itchyscratchy]

Can a Mrashall head rated at 4 ohms at a 100 watts can it be connected to a 8 ohm and 16 ohm cabinet at the same time? 1 output on the amp would be for the 8 ohm cab. and the other output would be for the 16 ohm cab. will this be ok? or would it be bad because its not the same ohmage? any advice would help.

[Tom Phillips]

Itchy,
It can. But... you have not said what you are trying to achieve. Or which Marshall head. One of the robust models with a big iron output transformer or one of the 100 Watt models with an OT the size of a 50 W amp? You also have not supplied any information about the speaker cabinets other than the impedance rating.

Having said that I can give you some facts about the operating conditions with the 8 and 16 Ohm cabinets connected in parallel to a 100W amplifier with a 4 Ohm output impedance.

1. The resulting load on the amp will be 5.33 Ohms
2. The amp will put out a little less power than it would with a correctly matched load. Let’s assume that the output power drops to ~75 Watts
3. The power would not be shared equally by the speaker cabinets.
   The 8 Ohm cabinet will see 50 Watts
   The 16 Ohm cabinet will see 25 Watts

There are other variables that could be discussed but they won’t significantly change the outcome. I personally don’t think that the mismatch between the 4Ω amp and the 5.33Ω load will cause a problem for a well designed amp in good condition. However, I’m sure there are people out there who will say that it will be bad.

HTH,
Tom

[J M Fahey]

Even more important: is it a Tube head or an SS one?
I can't automatically assume it's either one or the other.

[itchyscratchy]

It's a Marshall g100r cd solid state. The one cab. is a Marshall 8 ohm 4x12 and the other is a homemade cab with 2- 8 ohm speakers wired in series witch makes it a 16 ohm cab. So what your saying is the output on the amp ( with 2 outputs ) is a 100 watts with a 4 ohm load. Would it be the same for the other output with a 4 ohm load 100 watts? Would that mean it's putting 200 watts out?

[Tom Phillips]

Even more important: is it a Tube head or an SS one?
I can't automatically assume it's either one or the other.

Very good point. I wrongly just assumed a tube amp.

It's a Marshall g100r cd solid state. The one cab. is a Marshall 8 ohm 4x12 and the other is a homemade cab with 2- 8 ohm speakers wired in series witch makes it a 16 ohm cab. So what your saying is the output on the amp ( with 2 outputs ) is a 100 watts with a 4 ohm load. Would it be the same for the other output with a 4 ohm load 100 watts? Would that mean it's putting 200 watts out?

Your amp will only has one 100W power section and both speaker jacks are connected in parallel so you will not get 200W total.
It won’t hurt your amp to hook up both your cabs. Just try it and give a listen test. The power output will still be less than 100W and the power sharing will still be unequal between the cabs. Make sure that the cabs are in phase.

Have Fun,
Tom

[itchyscratchy]

So I have to hook up 2- 8 ohm cabs to get the 100 watts. Now is that 2-8 ohm cabs hooked together or 1-8 ohm per output?

[Ronsonic]

Can a Mrashall head rated at 4 ohms at a 100 watts can it be connected to a 8 ohm and 16 ohm cabinet at the same time? 1 output on the amp would be for the 8 ohm cab. and the other output would be for the 16 ohm cab. will this be ok? or would it be bad because its not the same ohmage? any advice would help.

I saw this was a SS amp later in the thread.

Yes, this will work fine. More power will go to the 8 ohm cab than the 16. If that's okay with you, it's okay with the gear.

[Tom Phillips]

So I have to hook up 2- 8 ohm cabs to get the 100 watts. Now is that 2-8 ohm cabs hooked together or 1-8 ohm per output?

Connect one 8 Ohm cab to each jack to end up with a 4 Ohm total load

[itchyscratchy]

I thank you guys with the info you gave me.