Shahinian Oblisk

Kgk, Rcprince is right on with the 4 ohm tap. The "OHM" is the resistance your speaker presents to your amp. By selecting the proper tap on the back of the Mcintosh, the amp will run in its most linear state. That's a good thing. If whatever speaker you use is between the 2,4 and 8 ohm taps, use the tap that is the lower of the two. Enjoy.

I'm no technical guy, but Onemug is right. A tube amp, other than an OTL (output transformerless) design, uses an output transformer to match its output with the impedence load your speaker presents. A solid state design generally does not use an output transformer and thus does not have different taps. The taps represent different points in the transformer windings (a transformer is wire wound around a core)that are optimal for the load in question. Outside of that I can't tell you too much, I'll leave it to a more technically inclined poster to correct me/elaborate for you.

By the way, I noted another post where you were asking about speakers to go with your new amp--don't be too anxious to change the Shahinians quite yet until you listen to them a while with the Mac, you might be able to resist the upgrade bug. The Shahinians are similar to my speaker system in terms of being closer to an omnidirectional speaker than the other, forward-firing designs you mentioned in your other post, and as such they present music in a significantly different manner than those other speakers. If you like and are accustomed to the Shahinian "sound", you might have trouble listening to more conventional designs. The other designs may do some things far better, such as pinpoint imaging and presentation of low level detail, but the overall listening experience might not be as pleasurable.

I agree with all of the above, including Newbee. That is, the "typical" installation will have the speakers connected to a tap that is equal to or lower than the nominal impedance of the speaker. That can vary though depending on how accurate the nominal impedance of the speaker was rated and / or the actual impedance taps of the transformer itself.

It is quite possible that a tap that is higher in ohmic value may sound better with a given speaker. In such a case, the only real potential drawback that i see is that distortion may be a tad higher, damping factor slightly reduced and / or tube life might be shortened slightly. That's because the slight impedance mismatch will end up pulling more current through the tube than if a lower impedance tap was selected. Even then, i don't see this as being a major concern so long as on isn't consistently wailing on the throttle of a tough to drive speaker. The bottom line is that one should experiment in such a situation, but be careful and use common sense. Sean
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A very astute suggestion by Newbee. Try all of them and choose which voice you sounds best to you as none will cause any damage to your amplifier or your speakers.