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A Question of Quality …
Valve amplifiers have recently risen to prominence in the world of high quality audio after years in the wilderness following the introduction of high-
Solid state amplifiers can be built more cheaply than valve amplifiers, because the transformers used in the output stages of valve amplifiers are expensive to make -
One of the greatest advantage that valve amplifiers have lies in the power supply design. Valve amplifiers work with much higher power supply voltages than do transistor amplifiers. Several hundred volts is the norm, compared with a few tens of volts in a transistor amplifier.
As the output power is proportional to the product of the voltage and current, it is fairly obvious that at any given power, the currents flowing in the valve amplifier’s power supply will be less than those in the transistor amplifier. Almost all of this current comes from the smoothing capacitors in the power supply. This would not be a problem in the transistor amplifier if perfect capacitors were used, but unfortunately, all capacitors have trade-
Further Advantages …
A further advantage to valve amplifiers, which is also often credited with the increased clarity, is the more linear behaviour of valves. Passing any signal containing more than one frequency through a device that is not completely linear results in intermodulation distortion. This effect is put to good use in FM modulators, but is not such a good idea in an audio amplifier, since it results in the generation of distortion products which are at frequencies harmonically unrelated to the original notes. It is likely that these products are responsible for the harshness that is heard in transistor amplifiers.
Most manufacturers test their equipment with sine waves, which will show up harmonic distortion, but will not reveal intermodulation distortion, so a good THD figure in the specification will not necessarily be a guarantee of a pleasing listening experience.
All Ming Da amplifiers use the ‘point-