The power transformer by magnetic field, electromagnetic induction and circuit interference to the amplifier, is the largest source of sound interference machine. So, to deal with its working condition and application environment, can effectively avoid the interference caused by the power transformer, the amplifier has excellent sound effects. I will do a discussion with you this.
1, power transformer in addition to the amplifier power supply, but also to the amplifier coupled to a power source, the source of disturbance in the grid into the amplifier, also will be generated in the amplifier voltage and current changes reflected to the power grid. In order to cut off the winding between electrostatic field and capacitive coupling, isolation and common mode suppression resulting interference, avoid grid circuit or the common mode voltage coupling to secondary or primary in, power transformer winding Gafa La Di electrostatic shielding of the sound is crucial. The shielding can layer alternate between copper foil, can also be complete to form the shape of structure, in short for winding (especially to the primary winding) surrounded by more, common mode rejection, the better.
2, magnetic interference generated by the power transformer amplifier has been troubled by quality problems, even if there is a pure power, magnetic induction from the amplifier can also cause a serious decline in quality. Due to the magnetic shielding cover high price (even higher than the transformer itself, which is why some import transformer high prices of reasons), general domestic machine rarely used magnetic shielding cover off the transformer magnetic interference, a lot of it is just a simple metal cover isolation, or simply will transformer exposed installation, so can't for effective magnetic shielding. Foreign high-quality transformers often used multilayer manganese alloy and crude copper interphase layer structure, surrounded the transformer, hand using manganese alloy high resistance, high magnetic guide the characteristics of magnetic circuit, eddy current induced by copper layer on the other hand have arrived in a magnetic field and interference of opposite magnetic field demagnetizing interference, so greatly reduces the leakage of the magnetic field of the transformer. Amateur conditions is very difficult to obtain manganese alloy cover, but also available in 1.5 mm soft iron and copper made multilayer structure of the magnetic shielding cover.
3, when the primary impedance transformer with reflection source resistance equal to the parallel resistor load will appear when the value of the low frequency cutoff, noise increases due to the transformer, so the power transformer must have enough inductance. But this should not be blind to the transformer output power of reason. Because the primary inductance of the transformer is changed with the iron core magnetic flux density and the secondary load power hour, iron core magnetic flux density decreases, the inductance decreases. In general, the power supply transformer in the secondary supply power of 1.4 - 2 times more appropriate choice.
4. The high quality of the transformer core permeability is high, the magnetostrictive effect is also high, influence of external magnetic field, pressure, vibration sensitive can therefore produce additional voltage, cause interference. Therefore, in the assembly or installation of transformer.
We should take the following measures:
- core or shield assembly before demagnetization.
- avoid core short-circuit, eddy current, magnetic flux decreases, the inductance decreases.
-Transformer should be vacuum impregnation, the lamination can be mobile.
-The transformer shall be installed on the damping base, any magnetic field source to damping installation.
- if the installation space allows for transformer shall carry out acoustic isolation.
5, the form of transformer is very important to reduce interference. In general, the transformer ring or O type high efficiency, small magnetic leakage,
But the flux is easily saturated, but not conducive to resist the power interference. Type EI is opposite, and because there are some
The air gap, the permeability of core stability. Between the R type is between the two. Because the grid pollution in our country is relatively strict
Heavy, so many "fancier" to choose more EI transformer as an acoustic power.