Impendance taps setting on a tube amp


I have decided to try out the Rouge Audio Cronus Magnum integrated amp before I upgrade my speakers. Reading a Cronus review, I understand that the amp comes factory wired to the 8 Ohms taps. To switch to the 4 Ohms setting you actually have to remove the cover and fiddle with the wires a little. The 6-Moons reviewer suggested requesting that the amp be wired to match the owner's speakers' impedance to avoid having to do it yourself.

I currently have the Totem Hawks speakers, which have a nominal impedance of 6 ohms. Here's a quote I got from Totem: "The Hawk exhibits a nominal 6 ohm impedance that is very constant throughout the ban. The minimum is 5.2 ohms."

Given this information, what would be the optimal setting: 4 or 8 Ohms? Should I try both and see what works best? That's pretty much what RA recommended, but I wanted to see what others think or perhaps faced a similar dilemma.

Thank you.
actusreus

Showing 4 responses by actusreus

Wow, yeah, I guess I now appreciate the built-in meter and easy biasing process with the Cronus even more. In fact, I actually enjoyed doing it for the first time with the biasing tool provided with the amp. I also purchased the Cronus as a "temporary" amp before I can upgrade to a tube preamp and power amp combo; once that happens, I won't have to worry about the internal impedance taps, hopefully.

All that aside, the Cronus is a wonderful amp. It actually made it possible for me to listen to CDs again.
Thank you all for interesting responses. I'm not sure why RA decided to keep the taps inside, but I assume there must have been a good reason for it. Here's an excerpt from the Cronus manual regarding the impedance setting:

The Cronus also provides options for either 4 or 8 ohm speakers. The impedance selected will depend on the speakers used. Consult either the owner's manual for your
speaker or your local dealer to determine the correct choice. The amplifier is factory set to 8 ohm.
To switch impedance setting:
1) Using a #2 phillips screwdriver, remove the top cover or deck.
2) Using a 5/16” wrench, remove the outermost nut from the positive (red) binding post.
3) Remove the 8 ohm tap (green wire marked 8) from the binding post. Be careful to leave the black wire with heat shrink on the post.
4) Remove the polyurethane tubing from the unused 4 ohm wire (yellow) and lug.
5) Place the 4 ohm wire onto the binding post and replace the outer nut.
6) Place the polyurethane tubing on the 8 ohm wire and lug.

Not looking forward to fiddling with this, I must say. I just hope it sounds more complicated than it actually is...

Another point I wanted to make and see what you guys thought about it is the fact that most speakers' impedance is not linear but varies across the frequency spectrum. Out of curiosity I went through a few copies of Stereophile yesterday and checked the graphs in the tech specs section. All of the speakers reviewed including ones in the $30-40K price range exhibited impedance that was both above and below the specified nominal impedance. If that's the case, 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?
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.
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.