A 4 ohm head with an 8 ohm cabinet

[pandamonk]

I was considering picking up a Marshall Valvestate 150 watt guitar head, and using it with my 8 ohm Marshall cabinet. The minimum ohm rating of the head is 4 ohms. I know it's safe to do so, since one fellow at Marshall already told me that's okay, plus in the manual they discuss which jack to use if you are going to be playing an 8 ohm cabinet.

Thing is...what about wattage loss and volume loss? If I use a 4 ohm head on top of an 8 ohm cabinet, is the amp effectively only putting out 75 watts then? And then I will lose some punch and volume?

Is there a reason hybrid amps and all solid-state amps don't have impedance switches like tube amps do?

The loss from 150w to 75w is 3dB. +3dB is a doubling in power, and +10dB a doubling in audible volume. To increase the volume by 10dB, you need 10x the power. To increase 3dB you need 2x the power.

So a small amp outputting just 25w can still give loud results. Just 6dB less than a comparable 100w.

 

[Farview]

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If my SolidState Laney Linebacker 50 reverb (from the 80's) head has 2 speaker outputs rated at 4 Ohm. Still don’t how they are setup exactly, parallel…I’m waiting for a response from Laney.

The combined speaker outputs are 4 ohms. Meaning, you can plug a single 4 ohm cabinet into one of the outputs OR you can plug two 8 ohm cabinets into those two outputs.

The rating on the outputs tells you which tap off the transformer the jacks are hooked to.

There is one 16 ohm jack for a 16 ohm cabinet.

There are two 8 ohm jacks for one 8 ohm cabinet OR two 16 ohm cabinets.

There are two 4 ohm jacks for one 4 ohm cabinet OR two 8 ohm cabinets/

But what if ad an extra mono plug on the cabinet and hook-up two Celestion 12" 8 Ohm in parallel to it?
In other words, one parallel pair per plug. wich gives two 4ohm inputs, right?

Yes. Two 8 ohm loads in parallel will give you a 4 ohm load.

.So then i can plug the two 4 Ohm output of the head in the two 4Ohm input of my cabinet...wich will give me the max I can get from my cabinet.

No. That would be a load of 2 ohms. The outputs on the amp are parallel.