Tonewin Tube Amplifier,from China
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We provide custom-made 

output transformers, 

power transformers 

for hifi amplifiers and 

guitar amplifiers. 

Welcome to your cooperation.

What is Hi-Fi?

"Hi-Fi" is the abbreviation of the words "High-Fidelity", meaning the audio equipment should reflect the original sound signal “as is” with as little change as possible. Theoretically, the original signal should not be deteriorated or modified in any way. The Hi-Fi concept is similar to photography, in that it requires a true reflection of the object onto film. Listening to some CD players, Phono Cartridges, Audio Amplifiers, and Loudspeakers, even those reaching very high standards in Hi-Fi quality, can result in a less than pleasant experience due to various distortions and colorations. For example, in an ideal World, an amplifier would be a straight wire with gain. However, due to various circuit designs and variable component quality, the ideal amplifier concept is not always an easy goal to achieve. Loudspeakers, being mainly electromechanical devices, also tend to exhibit variable results to the listener when comparing them to the original source of the sound and performance. It is only through the dedicated Research and Development of all of the products used in sound reproduction, that the theoretical goal of reaching sonic perfection to the original sound can be realized.

Why Vacuum Tube Amplifier?  

Vacuum tube amplifiers have always been the amplifier of choice for the working musician and their superb sound quality has always been recognized. Musical myth has ascribed almost magical tone to them. While the results may not be entirely magic, tubes do have a sound that is different from solid state amplifiers, and one that happens to make amplified music sound better to the human ears and brain.

In the early 80s, the invention of digital recordings in the form of CDs, MDs, etc. has gradually led to the fading out of such form of traditional recording as turntable records and analogue audio tapes. Yet some audiophiles reckon that the sound so reproduced by these digital recordings is rather rigid and artificial. With the use of tube amplifier, many agree that the reproduced music sounds much smoother and natural, particularly in terms of ambience, hall depth effects, instrument separation, human voice and harmonics.

The real reason to use tube amps is therefore simply that they sound better.

What is Class A, B, AB, Ultra Linear?

1. Class A means that the power tube conducts the same amount of current all the time, whether idling or producing full power. Class A is very inefficient with electricity but usually gives very low distortion.
A. There are single-ended class-A, or SE, amplifiers. They use one or more tubes in parallel, which are all in phase with each other. This is commonly used in smaller guitar amps and in exotic high-end amplifiers. Many audiophiles prefer the SE amplifier, even though it has relatively high levels of even-order distortion. Most 300B high-end amplifiers are SE. Negative feedback, which can be used to decrease the distortion of an amplifier, is felt by some people to sound inferior. Most SE amps have no feedback.
B. Push-pull class-A amplifiers also exist--they use two, four or more tubes (always in pairs) which are driven in opposite phase to each other. This cancels out the even-order distortion and gives very clean sound. Push-pull Class A operation usually involves low plate voltages and high plate currents, compared to Class AB operation below. The high currents might tend to wear out the tube cathodes faster than in an AB amplifier.
C. There are two kinds of class-A operation, which can apply to single-ended or push-pull.
Class A1 means that the grid voltage is always more negative than the cathode voltage. This gives the greatest possible linearity and is used with triodes such as the SV300B, and with audio beam tetrodes and pentodes.
Class A2 means that the grid is driven MORE POSITIVE than the cathode for part or all of the waveform. This means the grid will draw current from the cathode and heat up. A2 is not often used with beam tetrodes, pentodes or triodes like the SV300B, especially in audio. Usually a class-A2 amplifier will use tubes with special rugged grids, such as the SV811 and SV572 series of triodes.
Class A2 also requires a special driver circuit, that can supply power to the grid.
2. Class AB applies only to push-pull amplifiers. It means that when one tube's grid is driven until its plate current cuts off (stops) completely, the other tube takes over and handles the power output. This gives greater efficiency than Class A. It also results in increased distortion, unless the amplifier is carefully designed and uses some negative feedback. There are class-AB1 and class-AB2 amplifiers; the differences are the same as were explained above--the tube's grids are not (AB1) or are (AB2) driven positive.
3. Class B applies only to push-pull amplifiers in audio; it SOMETIMES applies to RF power amplifiers with one tube. It is like Class AB, except that the tubes idle at or near zero current. This gives even greater efficiency than Class A or AB. It also results in increased distortion, unless the amplifier is carefully designed and uses some negative feedback. If careful design is not undertaken, the result may be crossover distortion, which appears at the midpoint of the output waveform and has very bad-sounding effects in audio. Most solid-state audio amplifiers use class B, because the transistors undergo less heat stress when idling.
4. Ultra Linear operation was invented by David Hafler and Herbert Keroes in 1951. It uses only beam tetrodes or pentodes, and special taps on the output transformer. The taps connect to the screen grids of the tubes, causing the screens to be driven with part of the output signal. This lowers distortion considerably. It is usually seen only in hi-fi amplifiers that use power tubes such as the SV6L6GC, SV6550C, EL84 or EL34.

When should I replace the tubes?

Practically speaking, you should only replace tubes in an audio amplifier when you start to notice changes in the sound quality. Usually the tone will become "dull", and transients will seem to be blunted. Also, the gain of the amplifier will decrease noticeably. This is usually enough of a warning for tube replacement. If the user has very stringent requirements for observing tube weakening, the best way to check tubes is with a proper mutual- conductance-style tube tester. These are still available on the used market; though new ones have not been manufactured in many years. One tester is being manufactured today, the Maxi-Matcher. It is suitable for testing 6L6, EL34, 6550 and EL84 types. If you cannot get your own tube tester, speak to a service technician for his recommendations.

Are high performance cables worth the high price?

Speakers sound only as good as the cables used to connect them, so don't let low-grade speaker wires be the weak link in your audio system.
The supporting technology of great speaker cables is quite clear. In order to send an audio signal from one end to another with minimal signal loss, you require:
A proper thickness (lower the gauge, thicker the cable)
High ranked (99.99%) Oxygen Free Copper (OFC)