Z
zuel69
Active member
The reason why the load resistor is set higher than the selected impedance of the amp selector is because a 100 watt Marshall head at full volume into a resistive load set to the same impedance as the head will put out way over 100 watts, try 160-180 watts. This is because the amp will go into class B mode. When a cabinet is being played at full volume its impedance climbs, especially higher if it is a sealed closed back cabinet. This higher load tends to keep the amp at around 100 watts. A head played into a resistor of the same value will fry the primary windings of the transformer due to the excessive A.C. currents. So increasing the load resistor by at least twice sort of keeps the A.C. currents in the range that the output can deal with, at full volume.
This is very interesting, and may lend some credit to Ho's ultimate attenuator design.
This is very interesting, and may lend some credit to Ho's ultimate attenuator design.