4 ohm or 8 ohm tap on old tube amps?

07-22-12: Rrog
Hifitime, KT88's post sounds impressive, however, VTL and Manley Labs have always provided only one output on their amplifiers set at approximately 5.5 ohms for the best sound with the majority of speakers.

Yes, they did it by choice. However, you can see some significant differences in this test done by Stereophile. It really shows in the power output differences between the 4, and 8 Ohm output power measurements. Without the other impedance taps, we'll never know how it would compare sonically, to its one fixed output.

Hifitime, KT88's post sounds impressive, however, VTL and Manley Labs have always provided only one output on their amplifiers set at approximately 5.5 ohms for the best sound with the majority of speakers.

I think user name KT88 gives an idea of what happens in this other thread.

Yes I heard about the damping factor. My bass is really tight for an old tube amp, and I wonder if the system will be less so on the 8 ohm tap. I'll try it tonight and post back.

BTW I read on some site that Sid Smith and Saul Marantz disagreed about whether there should be a low frequency filter built into the 8B to filter out turntable rumble, so they compromised and made the "test" outputs without the filter (as Saul wanted) and the normal outputs with it, as Sid Smith wanted. So the "test" outs are the ones to use.

Jim

One advantage of using the 4- versus 8-Ohm tap is that the amp will have twice the damping factor so the bass probably will sound better damped...which may be better or may be worse.
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You can decide which tap you like better based on person taste, but you should also listen for which tap gives better power transfer. One tap should sound more powerful and that is the tap that matches best with your speakers.

I find in general the higher the impedance tap used the better the sound. As Mechans says just try both taps, your opinion may differ.Trust what you hear.
Regards,

I agree with Mechans here...Using a 4 ohm tap won't hurt anything with 8 ohm speakers...I have usually found 8 ohm taps work best, even with 4 ohm speakers...but your milage will very much vary on this...just try it..

I tried the different outlet taps on my tube amps with the speakers I was going to use and simply listened for the sound I liked best. It has worked out very well in a couple of different, amp/speaker combinations, without damage to amp or speaker. My advice use the tap that sounds the best

Since speakers are not a consistent impedance over there whole frequency range you really have to try both taps and see which you prefer.
Alan