The role of tone control circuit is used to adjust sound to conform to requirements of a variety of listening, to compensate for defects or audio recording of the frequency response of speakers, etc., because of its relatively simple structure and use, the negative effect of less thus the general conditions of the users, use the tone control can be, *, its use in the audio system plays an important role, in some users view a stereo system, particularly in the audio power amplifier to the principle of simplicity as the is on the extra features in the signal path to reduce the circuit to achieve the effect of authentic listening, I also agree that this argument is that if you already have enough high-grade fever speaker unit, which reached a high frequency response the ideal curve is relatively flat, this argument is right, and most people use the cabinet unit is owned low-cost general cargo market, with the tone circuit to improve its high frequency extension, the effect is quite listening A small investment a quick way.
  The types of audio circuit and the feedback RC attenuated both sides of species, as well as introduce the AA website price class tone circuit (actually
RC attenuated, but before the amplification stage with a AA class), both have advantages and disadvantages of the circuit, RC circuit due to passive components, circuit stability, and phase characteristics of a good, but the signal to noise ratio is poor, around the level of the input amplifier output impedance are higher, and susceptible to external magnetic field aggravation, there is a range of high-low bass control. Negative feedback tone circuit has some gain, signal to noise ratio high, nonlinear distortion small, the circuit dynamic range, but due to the depth of the negative feedback circuit in the state, if the layout design is easy to produce unreasonable self-excited, the above advantages and disadvantages of the two circuits, this site decided to use feedback to match the tone circuit site SSE01/SSE02, the shortcomings of the reasons is that it can well be overcome in a reasonable layout, while the op amp output and inverting joined the anti-self-excitation input phase compensation capacitor, the op amp's power supply pin 4,8 pin position recently joined the power decoupling capacitors, so a higher conversion rate for use of circuit design and layout requirements of high fever Win AD827/OPA2604 tone control to create the conditions do not use RC circuits is another reason this site has come up with the AA and is scheduled to make a product pitch boards in practice and SSE01/SSE02 board is not ideal and the signal-noise ratio with susceptible to aggravation of the magnetic field power transformer, so give it to re-design described below SSE06 HIFI tone plates, in real time with the site SSE01/SSE02 board op amp by replacing the different, are quite satisfied with listening to results.
  Picture this subject as follows:

Tone control circuit as shown above, from W1, W2, W3, W4, respectively, to achieve the treble, alto, bass, balance control circuit, the volume of the circuit board has been the site of the SSE01/SSE02 with volume potentiometer, it is not increased , volume potential as one of the op amp U1-level signal before the buffer amplifier, R3/R2 value is between 1-5 times, the site is set to 2 times magnification, you can change according to the actual situation of the source to adjust the value of R2, in the signal path capacitors C2, C4, C7 greater impact on sound quality, with high product quality German Red fever WIMA capacitors
  Capacitors, high-quality selection of operational amplifiers U2 op amp AD827/OPA2604/NE5532 fever can be, the performance of different sounds, Shaoyou be selected according to their own preferences, the former grade fever, see the op amp sound characteristics. The figure above, and common power amplifiers in the bass and treble tone control, only difference is the addition of tenor control the control circuit, in the listening, the IF part and the presence of music is closely related to IF is too bright or thin spot will lead to distortion by the W2 income-related external components constitute 1000HZ-2000HZ IF signal with 6-10dB of the increase or decrease, reaching frequency control.

Here in the design of the power switch to the active form LM317/LM337 servo power supply, the active form than the 78/79 series compared to the servo power supply internal resistance and low noise in an order of magnitude greater ripple rejection, and Kubota some relatively complex power structure with a simple style, performance and stability advantages, although the increase in the cost some, but the actual use of quality improvement is quite obvious. Schematic shown above, the input voltage is 18V AC Dual 12V-double can be, which affect the accuracy of the resistance voltage R14/Re14, R15/Re15 parameters to be consistent, so as to achieve a good symmetry of positive and negative power supply, the output voltage value is not some double-15V, but to achieve the same positive and negative voltage (typically two-op amp voltage DC 12V-15V can be double work)