Impendance taps setting on a tube amp

Wouldn't the arguments about "light loading," considerations about losing power or halving power be rather moot in practice, given the fact that the amp is presented with different loads depending on the frequency?

My feeling is that those considerations are not made moot by variations in impedance vs. frequency, they are just made less predictable, and the need to judge by listening is given greater impetus.

Since maximum power levels are typically required in the bass region, though, I suppose that some sense of the degree of power sacrifice that would result from "light loading" could be had by assessing the degree to which the speaker impedance in the lower part of the spectrum is greater than the impedance that the tap the speaker is connected to is nominally intended for (if in fact it is greater!).

Another point to keep in mind, though, related to that part of the spectrum, is that for a given amp design output impedance is lower at the 4 ohm tap than at the 8 ohm tap. Everything else being equal that will result in better damping of back emf from the woofer, and tighter control of the woofer, as Phil indicated in the first response above. So that is one more tradeoff that is involved, along with the others that have been mentioned -- reduced maximum power vs. improved woofer control.

Regards,
-- Al

So what was the verdict? How did each tap sound and which was better?

I settled for the 4 Ohm setting, but didn't listen long enough with the 8 Ohm setting to provide meaningful feedback. I started with the factory wired 8 Ohm setting and thought the volume wasn't loud enough so I assumed the 4 Ohm setting was going to be better. That was after about an hour of listening. The 4 Ohm tap sounds great so I didn't go back to comparing. The difference between volume levels is almost negligible but I think the 4 Ohms setting provides an overall optimal performance.

You might want to swap back once you've lived with the amp for a while. I have always found that the choice is very important for sonic reasons, and the right choice is not possible to predict based on the stated impedance of the speaker - even for the same amplifier.

Before you buy another component, make sure you know how each tap sounds. You might have a free upgrade hiding under the amp's cover :)

All great points Auxetophone. But I must tell you changing the taps is a b.i.t.c.h. It's not so much that you have to unscrew 10 little screws and remove the top cover through the tubes; it is the fact that on one side there is virtually no space for the wrench to get a good hold of the female thread. I had to maneuver for quite a long time before I got the thread removed and fastened to my satisfaction on the 4 Ohm tap. I'm not looking forward to doing it over again (and possibly yet again if I end up preferring the 4 Ohm setting). Interestingly, only one wire on each channel needs to be switched, which I don't quite understand since with external taps it seems there are always two extra terminals per each channel for each setting.