Search results
Results from the WOW.Com Content Network
Typical push–pull audio tube power amplifier, matched to loudspeaker with an impedance-matching transformer. Audio amplifiers typically do not match impedances, but provide an output impedance that is lower than the load impedance (such as < 0.1 ohm in typical semiconductor amplifiers), for improved speaker damping.
A speaker L pad is a special configuration of rheostats used to control volume while maintaining a constant load impedance on the output of the audio amplifier. [1] It consists of a parallel and a series rheostat connected in an "L" configuration.
This is called impedance matching or a matched connection. In this case, Z S = Z L, DF = 1/1 = 1 . The actual output impedance for most devices is not the same as the rated output impedance. A power amplifier may have a rated impedance of 8 ohms, but the actual output impedance will vary depending on circuit conditions.
The amplifier damping factor, which is the ratio of the nominal load impedance (driver voice coil) to amplifier output impedance, is adequate in either case for well-designed solid state amplifiers. Tube amplifiers have sufficiently higher output impedances that they normally included multi-tap output transformers to better match to the driver ...
Because of their inability to drive low impedance loads directly, valve audio amplifiers must employ output transformers to step down the impedance to match the loudspeakers. Output transformers are not perfect devices and will always introduce some odd harmonic distortion and amplitude variation with frequency to the output signal.
As cables between line output and line input are generally extremely short compared to the audio signal wavelength in the cable, transmission line effects can be disregarded and impedance matching need not be used. Instead, line level circuits use the impedance bridging principle, in which a low impedance output drives a high impedance input. A ...
Fortunately, the input impedance Z L of modern op-amp circuits (and many old vacuum tube circuits) is often naturally much higher than the output impedance of these signal sources and thus are naturally-suited for impedance bridging when receiving and amplifying these voltage signals. The inherently lower output impedance of modern circuit ...
Z in = the impedance seen looking into the input port when Z Load is connected to the output port. Z in is a function of the load impedance. Z out = the impedance seen looking into the output port when Z s is connected to the input port. Z out is a function of the source impedance. V s = source open circuit or unloaded voltage.