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Vacuum Tube Technology Overview
The basic purpose of the audio amplifier is to increase the current, voltage or power of a signal and deliver the signal to the speakers. The three basic types of amplifiers are solid state, hybrid (utilizes tube and solid state) and vacuum tube. Each technology has its positives and negatives. Although the general operational characteristics of the three audio amplifier types are similar, there is a differential in the sound.
There are two basic designs of tube amplifiers. One design is the triode amplifier (also referred to as single ended or Class A) in which one vacuum tube (300B, 2A3) is used per channel to amplify the audio signal. Within the tube, a small signal is placed on the grid which causes a large fluctuation of voltage. Thus, the small amount of signal controls the larger power so that the signal is replicated at a larger level of energy. Another design is the push pull amplifier (Class AB). Rather than using one tube, the push pull amplifier uses more than one tube per channel. One tube will amplify the positive portion of the signal and the other tube will amplify the negative portion. The push pull design provides greater wattage than the single ended amplifier. This is a very simplified rendition of how a tube amplifier works.
Why a Tube Amplifier?
The comeback of the tube amplifier as told by Rick Rosen of Stereophile is not a matter of nostalgia; it is a matter of excellent sound reproduction. Even the average ear can recognize the holographic soundstage, smoothness, and the crystal clear resolution that a tube amplifier can deliver. At low volume levels, the sound is clear and linear; at moderate volume levels, the sound is full and satisfying; and at loud volume levels, the sound will not punish your ears.
Aren’t Vacuum Tubes obsolete Technology?
No. Many people believe tube technology is obsolete since they think solid state has replaced it. One example used to exemplify obsolescence is the comparison of the small size and high computing speed of the personal computer (solid state) that has replaced the 1950’s Enac computer which used 18,000 vacuum tubes, had the power of a modern calculator and fit in a room the size of 3 double garages. No doubt integrated circuits are a significant technical advancement that has made many of the communication and computing devices of modern times a reality. However, tubes were never designed to be utilized as integrated circuits (on/off switching), tubes were designed to amplify. A good example of how tubes create power is your microwave oven (happens to be powered by a vacuum tube). Press the start button and your microwave oven will develop 900 to 1400 watts of power on demand. If that moderate sized oven used integrated circuits for power, it would be the size of a refrigerator. Tubes are still a $2.4 billion industry in the U.S. and is utilized in high power applications such as transmitting equipment, radar, RF equipment, x-ray machines, medical equipment to name a few. In relation to audio equipment, vacuum tubes perform superbly as an amplification source. From a technical viewpoint in terms of cost, size, power, reliability and performance, the vacuum tube amplifier is as viable as the solid state amplifier.
I have never used vacuum tubes before and they make me nervous?
In a sense, you have been using tubes all your life, light bulbs. Although the light bulb and the vacuum tube are used in different applications, there are some similarities in how they operate. If you drop a light bulb on a cement floor, it will break; you have to change the light bulb every so often; and last but not least, if a light bulb has been on for an hour and you grab it, then you will burn your hand. So it is with a vacuum tube.
Will I have to replace the tubes all the time?
In JoLida vacuum tube amplifiers, the vacuum tubes are rated to last a minimum of 3,000 hours. This is why we will guaranty them for 6 months to a year. For the average listener, this is approximately five years. The cost of replacing all the tubes on the JD 502B is $120.
How long can a tube amplifier last?
If maintained properly, a tube amplifier can last 30 years or longer. If you look in the classifieds for amplifiers for sale over 30 years of age, most of them are tube.
JoLida amplifers are only rated at forty, fifty watts of power output, that doesn’t seem like much power.
It is a rule of thumb that one tube watt is equivalent to two or three solid state watts.