| Author | Message | ||
     greg |
in most amps, when you decrease the resistance on the output, you increase the wattage. the opposite holds true as well increased ohms=decreased output wattage. what's the scoop with this amp? is the wattage the same(150w)if you switch between the four and eight ohm tap? what would happen if you put a four ohm load across the eight ohm output? i just found out that the output was wired in series, so i'm psyched that i can run both my 210 cabs if i want to, but i was just wondering if it affected the output wattage by doing so. thx greg | ||
| Steve Kennedy (admin) Username: admin Registered: 03-2002 |
Simply put, maximum power transfer requires matched impedance. If you set the output switch to 8 ohms, then the amp will develop its rated power RMS into a matching load (8-ohms). The output transformer tap impedance and the speaker load impedance match so this is the most efficient transfer of power. For example, if you leave the switch in the 8-ohm position but connect a 4-ohm load, the amp will develop less power because you are now at a 2-to-1 impedance mismatch and a larger portion of your output power is wasted as heat in the transformer and output tubes. In any case, if you match impedances you should get rated RMS power from the amp. Mismatching the impedance can cause the power to drop and generate excess voltage or temperatures that can damage the output transformer and prematurely wear-out the tubes. Mismatches also change the damping factor and frequency response. Since tube amps have an output transformer they tend to be very forgiving of mismatches and can "normalize" the output power. A music Man amp has a heavy-duty output transformer that can tolerate a 2-to-1 impedance mismatch just fine as long as the speaker impedance doesn't drop below 4 ohms or go higher than 16 ohms. This is not the case on a direct-coupled solid-state amp without an output transformer which generally operates as you described (until it clips, blows up or overheats). Solid-State direct-coupled amps can usually operate safely without a load, though. In a tube amp, the amp output power will be limited by its output transformer and load match. In a solid state amp, output power is limited by the size of the power supply or its protection circuits. Steve |