switching 8 ohm to 4 ohm output-output power reduction??

[pintail78]

If a take a 40 watt tube amp and plug the 4 ohm output into an 8 ohm speaker, how much power reduction (in watts) will I see at the speaker?

[Wilder Amplification]

When doubling the load you'll see a 50% reduction in power (which theoretically equates to only a 3dB reduction in perceivable volume), but the screen current on your tubes will increase as well.

[pintail78]

switching 8 ohm to 4 ohm output-output power reduction??

So, its a maz 38 which is split cathode biased, so the bias should be cool too. I run it with a Celestion G12h-30 (30 watts) 8 ohms, so I may use the 4 ohm output if I have to crank it up so i dont damage the speaker. Thanks.

[Wilder Amplification]

Keep in mind that 50 watts is the rated CLEAN power. Amplifiers put out much more than their rated clean power when cranked into clipping.