This paper presents a "Tube + integrated circuits" power amplifier, a voltage Larger bile tube, the former sub-frequency electronics, integrated circuits for power amplifier.
- Sources before the 6 N11-voltage amplifier, 6 N11 pre-electronic frequency, and the LM1875 power amplifier, the output power of up to 2 × 50W. This circuit tube and give full play to their advantages of integrated circuits, transistors both speed and frequency response, and have a good tube transient, warm crisp sound quality characteristics.
- Voltage amplififier and electronic sub-circuits are designed as a cathode output circuit, its output from the cathode tube, the output phase, the rate also keep up with the input of gate changes. With high input impedance, low output impedance, and the stability of nonlinear distortion of Higher a series of small advantages. This circuit with a class and after class LM1875 audio amplifier circuit connecting effective.
- Before the two-channel frequency can be overcome at the end of the general-level power-frequency network LC the existence of some shortcomings, the bass frequency and frequency Zhonggao Yin parted ways, to overcome the great amplifier of intermodulation distortion, and lower amplifier internal resistance and increase Damping amp, amplifier and speakers to better impedance matching. RC-circuit at a second active filter circuit. In order to overcome the RC passive network in the near-cut-off frequency band excessive rate of decline (up to 6 dB) of the defects, in this circuit used in the cathode output, thus significantly raising the band in the vicinity of Fen Pindian gain, improved Filtering performance, made after the output of the frequency of the more straight.
- LM1875 power amplifier and traditional circuit made to improve two areas: First, abolish negative feedback ground capacitance, a DC amplifier power amplifier (because LM1875 output offset voltage is very low, only 2 μ V); Second is to increase the R17 and R18 resistance, R17 for which self-contained air-defense which, R18 is the current negative feedback sampling resistance. The amp into DC current negative feedback amplifier, can overcome traditional AMPLIFIER stiff, dry deficiencies, its bass dive, Jiexi Li Zhong Gaoyin enhanced, in particular the current negative feedback circuit to a tube amp flavor, with a duct - Combined, is the icing on the cake.
- This amp shared two transformers, one for the exclusive use of duct; another dedicated to the LM1875 circuit, and a sub-2 Road 2 × 25V DC output, respectively, for the left and right channel, this would raise around Channel separation.
This mechanism has been completed, is extremely simple debug output to connect to four low-grade speakers (or false load), the first not to plug in bile duct, open the power supply to see whether tinder-smoking phenomenon. Gaizhui touch with after-amp input capacitance C8, C'8, speakers should be audible. Plug Power closed tube, open the power supply, connected to listen to audio, no abnormalities, then Speaker of normal audition.
VCD connection, you will be surprised to find that voice has changed over the past stiff dry the "digital flavor," punchy bass, Zhong Gaoyin bright slim, the sound quality really is Gangrouxiangji, gallstone complementary, pleasant-sounding.
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