Sunn Stagemaster

[luffy747]

I was recently gifted an old Sunn Stagemaster head. On the back it is labeled 250 Watts max and 2.5 Amps. The speaker outs have no Ohm rating. I can't seem to find much online about these amps. Does anyone have any idea what Ohm rating it is? Any other information about the amp would also be appreciated.

Images of the amp are included below.

[loudthud]

250 Watts is the power consumption from the mains. The power output is 120 Watts. The minimum recommended load impedance is 4 ohms.

[luffy747]

Thanks for the info! Please excuse my ignorance (I'm terrible at this Ohms thing), but does that mean that I should only use a 4 Ohm cab with it or would anything with 4 or more Ohms (since 4 is the minimum) be safe. If so what exactly would be the difference between using a 4, 8, or 16 Ohm cab?

[loudthud]

6, 8 or 16 ohm loads would work fine because they are above the minimum. The power delivered by the amp will be less than 120 Watts however. Typically the power goes down by half each time you double the impedance so figure about 60W and 8 ohms and 30W at 16 ohms. If you connect more than one cabinet you have to know the combined impedance that the amp is required to drive.

Two 8 ohm cabinets represint a 4 ohm load to the amp.
Two 16 ohm cabinets repersent an 8 ohm load to the amp.
Four 16 ohm cabinets represent a 4 ohm load to the amp.
One 8 ohm and one 16 ohm cabinet (or three 16 ohm cabinets) represent a 5.33 ohm load to the amp.

That covers most situations.