The function of the tone control circuit is to adjust the timbre in time to make it conform to various listening requirements, to compensate for the recording defects of the sound source or the frequency response of the speaker, etc. Because of its simple structure and use method, it has few negative effects. Therefore, for users with general conditions, the use of the tone controller is simple and reliable, and its use occupies an important position in the audio system. In the view of some netizens, the principle of simplicity is the principle of the audio system, especially the audio power amplifier circuit. In order to reduce the redundant function circuits in the signal channel to achieve the original listening effect, the author also agrees with this statement. The problem is that if you already have a high-end speaker unit with a fever level, its high and low frequency response reaches an ideal A flat curve, this statement is correct, and most of the box units used by ordinary people are ordinary low-priced market products, plus a tone circuit to improve its high and low frequency extension, it is still a considerable investment in listening An approach that is rare and quick.
There are two types of audio circuits: RC attenuation type and feedback type, as well as the AA type tone circuit that is priced at this site (in fact, it is also
RC attenuation type, only the AA of the previous stage is used to amplify). Both circuits have advantages and disadvantages. The RC circuit is a passive component, the circuit is stable, the phase characteristics are good, but the signal to noise ratio is poor. The output impedance is relatively high, and it is easily interfered by the external magnetic field. The other is that the control range of the high and low bass is small. The negative feedback tone circuit has a certain gain, a high signal-to-noise ratio, low nonlinear distortion, and a large dynamic range of the circuit. However, because the circuit is in a deep negative feedback state, if the wiring design is unreasonable, it is easy to produce self-excitation. The advantages and disadvantages of the two circuits, this station decided to choose a feedback tone circuit to match the SSE01 / SSE02 of this station, the reason is that its shortcomings can be overcome in careful and reasonable wiring, and at the output of the op amp and the inverting input Add self-excitation phase compensation capacitor at the end, and add power decoupling capacitor at the closest position of the power supply pin 4, 8 of the op amp, so that it is also used for the AD827, which has a high conversion rate and requires high circuit design and wiring / OPA2604 creates conditions for tone control, and does not choose RC circuits. Another reason is that the AA tone board made by this site is scheduled to be finished products. In fact, the signal-to-noise ratio is not ideal and easily susceptible when used with SSE01 / SSE02 boards. The magnetic field of the power transformer is dry, so it was abandoned and redesigned as the SSE06 HIFI tone board described below. When actually matching the SSE01 / SSE02 board of this station, by replacing different operational amplifiers, Reached a very satisfactory sound effect.
The tone control circuit is as shown in the figure above, and the treble, midrange, bass, balance, and balance control circuits are realized by W1, W2, W3, and W4. The volume circuit is already installed on the SSE01 / SSE02 board of this station, so it will not increase. , The volume potential, where the operational amplifier U1 is used as the buffer amplification of the previous stage signal, the value of R3 / R2 is between 1-5 times, the site is set to 2 times amplification, and the value of R2 can be adjusted according to the actual sound source. The capacitors C2, C4 and C7 in the signal channel have a greater impact on the sound quality. High-quality fever capacitors German Red WIMA capacitors are used. For the operational amplifier U2, high-quality fever op amps AD827 / OPA2604 / NE5532 are acceptable. You can choose according to your preferences. For the sound characteristics of the pre-fever op amp, please see contact us for a detailed description. Only the high and low bass controls are different from the tone control in the above picture and the common power amplifier. Control circuit, in listening, the intermediate frequency part is closely related to the presence of music. If the intermediate frequency is too bright or thin, it will cause distortion in the field. The W2 into the relevant peripheral components constitute the intermediate frequency of 1000HZ-2000HZ No. 6-10dB do to enhance or attenuate, to achieve the purpose IF control. 
In the design of the power supply, the active servo stabilized power supply composed of LM317 / LM337 is used here, which is an order of magnitude lower in internal resistance and noise than the active servo power supply composed of 78/79 series, and the ripple suppression is stronger, and Some relatively complex pit fields have the advantages of simple power supply structure and stable performance. Although the cost has been increased slightly, the improvement in sound quality in actual use is also quite obvious. The circuit diagram is as shown above, the input voltage can be AC ​​dual 12V- dual 18V, and the parameters of the resistors R14 / Re14 and R15 / Re15 that affect the voltage accuracy must be consistent, so as to achieve good symmetry of the positive and negative power supplies, and the output voltage value is not It must be double 15V, but the positive and negative voltages are consistent (generally the op amp voltage is DC double 12V-double 15V can work normally)
PCB board design drawing is as follows 
PCB design fully considers the strict requirements on the use of high-speed op amps. Add WIMA CBB decoupling capacitors closest to the IC power pin. The power supply of the circuit is far away from the small signal processing part, and ground isolation measures are added. And strict one point grounding wiring measures, use this board to get the best signal to noise ratio.
The following is a physical picture of the tone control board with high, medium, low, and balance made by the fever op amp introduced by this site recently customized from the manufacturer. 
1
2
3
Component selection : use fever components on the key components that affect the sound quality, decoupling capacitors use WIMA CBB 0.1U capacitors, audio cross-link coupling capacitors use WIMA 1U capacitors, C14 / Ce14 use genuine ELNA (S) high speed Complementary electrolytic capacitors, PCB board and SSE01 / SSE02 board are the same process, blue thick 2MM gold-plated board power input: AC dual 12V-double 18V can share the small voltage output group on the ring transformer.
Precautions for installation and wiring:
The signal input and output sockets are white pin sockets on the board. The socket near the large electrolytic filter capacitor is the signal output socket. The other is the input socket. It is best to use a special shielded signal line for the signal line to avoid AC magnetic fields. Dry. The power input socket is the blue terminal block on the board. Note that the ground marked in the middle is the ground wire. Don't make a mistake.
Note when used with SSE01 / SSE02 board of this site:
1. In order to reduce unnecessary noise, improve the signal-to-noise ratio, and save costs, netizens who have purchased the SSE01 / SSE02 board of this site should do some small work on the SSE01 / SSE02 board when they are additionally equipped with this board for pre-tone control. Changes, that is, disconnect or remove the previous magnified part of the board, as shown below
After the modification, the wiring can use the audio input socket on the original SSE01 / SSE02 board to directly connect to the signal output line of the SSE06 board introduced on this page, that is, the wiring process is: signal source-"SSE06 tone board signal input socket, SSE06 tone board signal output socket-"SSE01 / SSE02 audio input socket, connect the power supply, the speaker output, work when powered on. It should be pointed out that in order to avoid the signal line being affected by the AC power frequency magnetic field, it is better to use a three-core shielded line for the signal line.
2. Regarding the selection of fever op amps, the several types of fevers provided by this site include NE5532, OPA2604, AD827, and AD812. They are all DIP8 packages, which can be directly replaced on the front stage of the power amplifier board, but when used on this feedback tone board, Due to their different conversion rates and gain bandwidths, the capacitance of the phase compensation capacitor C6 / Ce6 will be different.In the high frequency 10KHZ-80KHZ square wave characteristic test, it is found that when U1 and U2 are both AD812 or AD827, do not add this phase There is no overshoot in the compensation capacitor in this frequency band, and there is no zero drift in the output pin voltage of the AD827 / AD812. In addition, the compensation capacitor has a square wave characteristic deterioration, and when using NE5532 / OPA2604, this compensation must be added. Capacitance, the value is 30-50P (33P for this site) high-frequency ceramic capacitors, used to eliminate the slight ringing of the square wave peak, on listening, through the above strict test value, with the post level of this site When the power amplifier board SSE01 / SSE02 board, it is much clearer and slimmer in the high-pitched area, the transparency is improved, and the superior performance of each fever IC is well played, and the simple mutual replacement usually does not achieve the expected effect. In addition to the buffer amplification operation in the test Put U1, the tone control U2 uses the same One type of op amp, that is, the code of this station is SSE06A (use NE5532x2), SSE06B (AD827X2), SSE06C (OPA2604X2), SSE06D (AD812X2). Also try to do other types of collocations can have better mid-high frequency Wave characteristic diagram A: NE5532 (U1, used as buffer amplification) + OPA2604 (U2, tone control), 33P for C6 / Ce6, codename SSE06E
B. Use AD827 (U1) + AD812 (U2), no phase compensation capacitors (cancel C6, Ce6), code-named SSE06F
Other combinations such as NE5532 / OPA2604 + AD827 or NE5532 / OPA2604 + AD812 ringing in the peak of 10KHZ to 80KHZ frequency, it is recommended not to adopt. The above two solutions can provide a reference for netizens who have purchased the SSE01 / SSE02 board of this site It is recommended that another point is that a good-performance op amp is used as U2, and the power amplifier board that directly drives the subsequent stage can play the excellent performance of the op amp.
Follow WeChat
Download Audiophile APP
Follow the audiophile class
related suggestion
This article mainly introduces the simplest tone circuit diagram (a detailed explanation of the eight analog circuit design schematics). Add a height to a power amplifier without tone control ...
This article mainly introduces the complete circuit diagram of the tube tone circuit (the schematic diagram of the six tube tone circuits). The tube preamplifier can play a role in digital sound source ...
The 3D tone circuit LM4610 made by LM4610 is an American NS ...
![[Photo] 3D tone circuit made by LM4610](http://i.bosscdn.com/blog/20/06/41/513636683.gif)
'+ data.data.username +' '; dom + ='
Scented Candle,Coconut Scented Candle,Luxury Scented Glass Candles
XINGYONG XMAS OPTICAL (DONGGUAN ) CO., LTD , https://www.xingyongxmas.com