SoundMods wrote:
B[color=#BF0000]ut don't power tubes like to "see" a high load impedance. It seems to me that most production tube amplifiers with output transformers have a compromise transformer to help deal with different speaker loads -- hence the different taps at 4, 8, and 16 ohms. The nominal impedance of my Altecs is 8-ohms, but the sound really opened up when I started feeding them from the 16-ohm taps. My 845s seem to like a higher plate load.
Paul Elliott's Magnepans have a nominal impedance of 4-ohms and yet when we ran them off of the 8-ohm taps of his them Monsoon amps. they opened up in a similar fashion. Paul's KT-88s liked the higher plate load.
When you connect an 8-ohm load to a 16-ohm tap, or a 4-ohm load to an 8-ohm tap, the output tube(s) is (are) seeing half the nominal primary impedance... Triodes tend to like a higher load impedance, pentodes tend (to a point) to like a lower load impedance.
Roscoe