4 ohm tap vs 8 ohm tap

Aroc,

You have received incorrect info. No matter which tap you use, the full primary of the output transformer is used, and on the secondary, the HIGHER the tap impedance, the MORE of the winding is used (for example, on an winding with 4, 8 & 16 ohm taps, the 4 ohm tap is the CENTER TAP).

Another thing--according to the Dynaco ST-70 manual, running an 8 ohm speaker on a four ohm tap reduces power, but "the operating conditions are shifted from maximum power output to minimum distortion."

And, yes, the damping factor will be higher from the lower tap. The great thing is that it costs nothing to find out which way sounds better, and will not damage your amp (if you turn off the amp before playing with the wiring). Luceeeee, you got some listening to do!

BTW, I am the designer of a tube power amp, and have been an electronic technician for over 30 years.

Hi Al. I would suggest listening to Al. He and I discussed this very same topic quiet some time ago. My speakers, Roman Audio Centurions are an 8-ohm rated speaker and I am running them on the 4 ohm taps on my tube amp. At first I didn't think there there would be a difference, but Al was right, there is. Try it and see for youself.

SHAMELESS PLUG: Al does make a really awesome tube amp, I use one.

Thanks for the corrections Al. I did a quick internet search and you are right on the money. Thanks again. Gotta watch who you get advise from!

Thanks, I just wanted to make sure there were no issues before I started running them like that for an extended period of time. I tried the 4ohm tap and I felt I liked it beeter that way.
Thanks again. Scott

Aroc,

Alraul is correct - the full primary winding is always seen
by the output tubes.

The different taps are on the secondary side of the the
transformer with higher tap impedance having more windings.

Hence the 4 ohm tap will have the fewest windings of the
set of 4, 8, and 16 ohm taps.

Dr. Gregory Greenman
Physicist