The circuit is shown in Figure 5. The driving stage adopts the new product TDA7294 from SGS-THOMSON. The internal driving stage and output stage of the chip use DMOS field effect transistors, which are powered by ± 40V, and the output power can reach 70W ( RMS / 8Ω), low distortion (0.005%), delicate sound, excellent hearing, it is one of the excellent chips in recent years. The power output VT1, VT2 adopts the famous Shanken high-power pair tube 2SA1216, 2SC2922 (VCM = 180V, ICM = 15A, PCM≥200W, fT = 50MHz). The circuit principle is as follows: the signal is input to the IC positive phase input terminal ③ pin via C1 and R1. R7 and R3, C3, and C4 connected to IC pin ② form a negative feedback network, and the closed-loop gain of this amplifier is about 34 times. The ⑨ and ⑩ pins are the standby and mute terminals, respectively. Because the time constant of ⑩ R and C network is larger than that of ⑨ pin, the switch is switched on in mute mode to avoid the impact of switching shock.
Figure 6 is a printed board diagram (one channel), the main points of production: an insulating mica sheet should be added between the metal cap of the IC and the heat sink (the metal cap is connected to the ⑧ foot). Power board (refer to Figures 3 and 4): 300W dual 28V ring, 4 50V / 1000μF filter capacitors, 50V / 100μF two, 100V / 0.1μF two, and 6A fuse tubes FUSE1 and FUSE2. The power supply part should be tested separately without first connecting the power amplifier, and measuring whether the positive and negative output voltages of the power supply are symmetrical, and the error should be within 0.6V. When testing the machine, for safety reasons, the lower voltage experiment (such as ± 25V) should be used first, and no signal is added. The DC voltage of the output terminal to ground should be measured within 20mV. According to the occasion used, the final current is smaller (about 6mA), if you want to increase, you can fine-tune R9. Power tubes must be strictly matched (within 3%) and genuine products are used. TDA7294 can use 60mm x85mm x 20mm 12-slot heat sink. For the output tube, a professional heat sink should be used. It is best to install a small fan to assist in heat dissipation (such as an axial fan on an old microcomputer switching power supply).
Follow WeChat
Download Audiophile APP
Follow the audiophile class
related suggestion
Avago Introduces New High Linear Power Amplifier Module Product Avago Technologies ...
The circuit is shown in Figure 1. The chip IC uses the LM1875 of the American NS company, which has a soft tone and low distortion (0.015% ...
The word "Monster" has both positive meaning and ...
When the output power of the digital power amplifier is greater than 50W, it is impossible to use only ...
If an "audiophile" is a group of people who are never satisfied with the sound and "loved the new and the old" with the audio equipment. Then just rely on these so-called "fever spirits" ...
First, the circuit principle and characteristics 1. Power amplifier part (see Figure 1)
There is a well-known saying in the Hi-Fi world that is "briefness first." This means that if ...
Simple and practical TDA2822M integrated power
TDA2030 is ...
STK465 thick film ...
This RF power amplifier can output 2-3 channel signals, covering an area of ​​about one square kilometer, is ...
The inverter introduced here (see Figure 1) is mainly composed of MOS field effect transistors and common power transformers. Its output power depends on MO ...
The cell area we refer to here refers to the radius
Author: Lin Changhao This article describes several mining ...
Low frequency power amplifier
Looking at the Hi-Fi amplifiers currently on the market, the output power is 100W ...
With the newly launched LM4651 and LM465 from National Semiconductor ...
EL34 (6CA7) was first launched by Philips in 1956 ...
This article cleverly combines the electronic tube EL34 and the transistor (op amp), ...
The pre-amplifier adopts a European-made TESLA brand low noise high cheek double transistor ...
"Simple" means the circuit of the amplifier is simple, making it easier, as long as the picture ...
1. Description: & nb ...
The Class A transistor power amplifier has a warm and sweet tone, which makes people tempted. But the temperature rise of Class A amplifier ...