Why does my tube amp

The interface between the amp and speaker is what makes for a good combination. Its not always the case that transistors can drive any speaker made and do the job correctly.

It may simply be that your speaker is designed to work with tubes and to take advantage of their characteristics (for example even though it is a 4 ohm load there may be a substantial impedance peak in the bass that transistors can't drive).

There are some very good reasons that there are still tube amps being made all over the world half a century after they were declaired obsolete! IOW you don't have to know anything about electronics if you understand this simple fact. In the meantime enjoy the music...

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.