Make 300B single-ended output machine with push-pull output transformer, 300B Power Amplifier
Keywords: Making 300B single-ended output machine with push-pull output transformer
Make 300B single-end output machine with push-pull output transformer
Single-ended output machine is rich, the sound is ostrich, listening to the ear, and is favored by gallbladder. The quality of the single-ended power amplifier has very close contact with the performance of the output transformer. The single-ended output transformer is to overcome DC magnetization. The core should have a gas gap. Therefore, the single-ended output transformer is large, high cost, and difficulty in pairing .
Since the single-ended output transformer is within the audio range of at least 20 Hz-30kHz or even a wide audio range, on the one hand, the amount of inductance is large to obtain a good low frequency response, and the iron core must be increased; on the other hand, require The leakage and distributed capacitors are as small as possible in order to get a good high-frequency response, while inductance, leakage and distributed capacitance are increasing or decreased.
In order to solve this contradiction, a larger core cross-sectional area is used to reduce the distribution capacitance to reduce the distributed capacitance to reduce the distributed capacitance to reduce the distributed capacitance to reduce the distributed capacitance to reduce the distributed capacitance to reduce the distributed capacitance to ensure high frequency response. Nevertheless, the single-ended output transformer produced in 15Hz to 50 kHz is already unwind, and the generating frequency response is more likely to be much easier, and the other power single-ended output transformer is much easier, and the volume is small. The cost is low, it is easy to match.
In order to further improve the comprehensive performance of the single Sirai, enhance the performance of the music, make the playback music more voices, the sound is better, fully reflect the beautiful sound of single-ended machine, and has a wide range of frequencies, if used The output transformer makes a single-ended output transformer to make a randers. It is a good choice. Below, the broadband ring 300B single-end output machine made by the author trial push-pull output transformer is made.
First, the principle of circuit
The motor circuit is shown in the figure, with audio dedicated five-pole 6b8p pushing the direct thermal triode 300b operation, the 300B screen is connected to the end of the push-pull output transformer, and the other end of the push-pull output transformer is connected by 6p3p. DC excitation. Circuit, when the 300b screen is determined, the 6P3P screen stream is adjusted to the 300B screen stream, and due to the opposite direction of the two sets of coils, the resulting DC magnetic field cancels each other, so single-end DC magnetization problem is resolved, thereby solving single-ended Output transformers must have a magnetic gap, making the problem of output transformer inductance, and realize the wish of making single-ended output transformers with push-pull output transformers.
At present, the frequency response of the high-performance push-pull output transformer has reached the range of 10 Hz-100kHz (-1dB), which is used for single-ended output machines, expanding the frequency of the traditional single-ended output transformer, and the sound quality tone is very bid , God, specially listening. Although this method is increased, the universal output of single-ended output is very rare, and it is precious.
Second, component selection
Electronic 6B8P audio-specific second-electrode / five-pole, originally used in AC radios and low-frequency voltage amplifies, and the diode can be grounded, the tube is strong, the gallbladder is rich, and the air is good.
300B domestic products have dawn, Guiguang, Tianjin full, etc., rectifying pipes with Nanjing 5Z3P. Big red robes, electrolytic capacitors, domestic days and card capacitors or flash dedicated electrolytic capacitors CD17H, etc., such capacitive charge conversion rate is fast, the dynamic and strength of the music is uniform, and the coupling capacitor selects a hint of the frequency difference transmission characteristics. Silver film Oil leaching capacitor or copper oil immersion capacitance, such as VQ silver film oil immersion capacitance, such capacitive, playing people's voice tone, if there is a feeling of it.
The push-pull output transformer of this unit is a dawn 50W 6P3P push-pull output transformer, the core is 30mmx50mm, and the single-ended output impedance (half arm) is 3kΩ: 8Ω, and the frequency is 10 Hz-100 kHz (-1dB). The power transformer power is around 300VA, and the blocking ring is 5H300mA.
Third, assembly debugging
After the whole machine is unmistered, the 6b8P cathode current is adjusted at 2.6mA (cathode voltage of about 2.6V), and 300b cathode current is adjusted at 62mA (cathode voltage about 68V), and then the 6P3P screen is also adjusted in 62mA, after a period of time After the machine, multiple work points are completed.
Listening to the machine, the source is the computer sound card, the speaker is the homemade 90dB / 12 inches of three-point frequency union speaker, the test is placed (opportunities), the sound is beautiful, high school low frequency performance, gallbladder, lively, delicate Accurate the positioning of the sound area, the people's voice is rich, very resistant.
Our other product:
