Why does my tube amp

The harder you push your amp the shorter the life of the power tubes.

Lower impedance + lower efficiency = shorter tube life.

Another thing to consider that there really isn't a good justification for low impedance if sound quality is your goal. **All** amplifiers, tube, SS and class D, have lower distortion driving higher impedances. If a tube amp has an output transformer (and most do, ours don't) then you will have wider bandwidth driving higher impedances as well.

Tubes, unlike transistors, can deal with higher impedances without loss of power. And you will find that the setup is less sensitive to speaker cables, as well as the output section of the amp (tubes and output transformer) are more likely to run cooler. So if you want to get the most out of your tube investment dollar, use a speaker with higher impedance- 8 or 16 ohms.

Great point, Ralph. Also, using a Speltz Zero autoformer can make a low impedance speaker look like a higher impedance. I'm loving the Zeros on my Infinity RSIIbs. No downside that I can hear at all, in fact the entire frequency range from low bass to airy highs sounds better with them.

Thanks Ralph, i should have talked to you a lot of $$ ago.