High-quality 12-level equal loudness preamplifier, NE5532 DC preamplifier, 220V power supply, good effect.
It can be used as an independent pre-stage after the CD or before the power amplifier. The American NE5532 op amp has DC amplification. There is no coupling capacitor between the input and output. The matching is strong, the load effect is small, and the connection effect is good. It is suitable for transistor or tube power amplifier.
This machine has a unique design, a wide range of uses, and good results. It can increase the high frequency and low frequency components at low volume, so that the loudness ratio of the low, medium and high parts remains the same as the loudness ratio at low, medium and high volume. With enhanced bass and treble characteristics, the sound is fuller and more stereoscopic.
12-step step switch assembly, continuously adjustable equal loudness, volume control. The route is complicated and the effect is first-class. Used for synchronizing loudness control such as pre-amplification and volume, which can increase the high-frequency and low-frequency components at each low volume, so that the loudness ratio of low, medium and high parts is maintained and the loudness ratio at low, medium and high volume the same.
High-quality 12-step step-by-step switch OEM Taiwan-funded enterprise production, used in instruments and electrical equipment. 12-gear dual channel with semi-circular copper handle, silver-plated internal contacts, long-life seal, excellent design quality, channel-to-channel resistance error of 12-gear potentiometer is far less than 1%, signal distortion is much smaller than common carbon film potentiometer, left and right The balance is high, the control is accurate, and there is no noise caused by the poor contact of the carbon film potential, and the service life is very long.
The position of the rotary switch is clearly defined, excessively smooth and flexible, and the hand feels light, just like the famous Swiss SWISS ELMA step switch, which is finely adjusted with smooth operation.
A NE5532 is used to amplify the front and back of the 12-gear potentiometer, 6 times before the potentiometer to amplify the tone volume insertion loss, 6 times after the potentiometer to amplify, there is enough gain and driving force, the use effect is very good, a complete pre Signal amplification circuit.
Of course, if you put on a high-gear op amp, you can add icing on the cake. Circuit board ± 15V DC power supply. The machine is quiet without hum.
The power supply is powered by a parallel type A regulated power supply: the adjustment tube is connected in parallel with the load, and the output current is constant. When the load current changes, the circuit will automatically adjust the current of the adjustment tube to maintain the output current unchanged, thereby stabilizing the output voltage . Therefore, the dynamic internal of the parallel type A adjustable regulated power supply is basically unchanged. Its AC internal resistance, ripple factor, transient characteristics and other technical indicators are superior to the general series stabilized power supply, and it is suitable for high-fidelity audio amplifiers.
Class A parallel regulated dual-voltage gold-sealed rectifier power board with low ripple choke filter, secondary capacitor inductance series filter, small ripple.
It is designed to provide high-quality supporting DC voltage for dual-voltage discrete component pre-stage and fever op amp lines. The choke is made of EI35 Z11 iron core, layered and segmented, and an iron-plated copper shield is added. Capacitance and inductance are connected in series with multi-stage filtering, and the ripple is extremely small.
The layered winding of the choke is not a mystery. It is very different from the conventional winding method. The reason is that the choke power supply is also part of the signal coupling channel. The reduction in leakage inductance and distributed capacitance affects the sound quality. Has a big impact, how many people will realize it?
The power transformer adopts EI iron core power transformer. The middle frequency is thicker and denser, and the high frequency is thinner. The transmission speed is slower than the C-type, O-type, R-type and other iron-core transformers. After the layering method, the pressure resistance, details and resolution have been significantly improved, and the high-frequency fine extension is also very good. There is a unique tone of the EI iron core power transformer-mellow and durable.
This is why many world famous machines still use the most traditional EI iron core power transformers.
The op amp is an original second-hand disassemble machine.
Features of carbon film potentiometer and step switch potentiometer:
Let's first understand the dimensional effect of the conductive performance of the semiconductor-metal conductor planar structure
The contact surface of two different materials generally produces a composite structure in which the contact barrier is composed of two materials with certain conductive properties arranged in sequence. Because the average confinement potential of conductive electrons of different materials is different, they are near the interface , Microscopically presents an unbalanced carrier diffusion pattern and potential gradient. The material with low confinement potential energy of conductive electrons near the interface exhibits a certain positivity, and the corresponding material with high confinement potential energy of another conductive electron presents a certain negative chargeability. It is a contact potential barrier, which can be called a potential junction, and the planar thin film structure is also called a "quantum pump" [3]. In terms of electrical conductivity, this internal interface structure has a certain degree of diode effect. The semiconductor PN junction is a typical interface potential structure.
Carbon film potentiometers have a history of hundreds of years and are as antique as the history of power coil speakers. The carbon in the carbon membrane potentiometer is a non-metallic element and is located in the second period of the IVA group of the periodic table. Its chemical symbol is C, its atomic number is 6, and its electronic configuration is [He] 2s22p2. Carbon is a semiconductor, and a carbon film potentiometer is made by coating a layer of carbon film on a horseshoe-shaped paper rubber plate. The carbon film body is formed by coating carbon black, graphite, quartz and other materials on the surface of the substrate. The rivets are used to fix the copper (or iron feet) as the lead-out solder legs. The carbon film plate and the copper feet are different. Conductor material, they form a semiconductor-like "PN" junction. A similar "PN" junction is formed between the sliding copper brush in the potentiometer and the carbon membrane plate. The current flowing through the "PN" junction will produce nonlinear distortion, which will affect the sound quality. Disadvantages to avoid. This is the reason and reason why the HI-END Ding audio does not use carbon film potentiometer.
The step switch is a contact made of all-copper materials, and there is no problem of nonlinear distortion, and the fidelity of sound quality is greatly improved.
