Author: Wang De Chao
The system configuration of the machine: new creation of a 30W semi-transistor power is pushing the speaker specializes in issuing, and the middle sound, the treble is issued by the radiator in the radio, and the audio signal is provided by the cassette recorder and the radio.
The power amplifier circuit is shown in the figure. Add the audio voltage at both ends of the input transformers B1, B2 primary coils L1, L4. After the B1, B2 is inverted, the base of the power amplifier tube BGL, BG2 is added, and the speaker in which the speaker is pushed, and the maximum amplifier is maximized. The output power is 30W.
In order to achieve an ideal bass effect, the input transformer's primary winding must be large enough. The single transformer is difficult to achieve, and thus use two input transformers B1, B2 to increase inductance, so that the low audio can be greatly expanded.
B1, B2 are allocated by the exact same two 25W line transformers. Demolition all the coils of the original transformer, with φ0.15mm enamel lines in the original skeleton, 3300 hints are primary (L1 and L4 in the right); the secondary φ0.51mm enamel wiring wrap around 96 (L2, L3 and L5 in the right), L6).
B1, B2 connection, as shown on the right, the "tail" of the B1 primary winding L1 (tail "(in the figure" • "end)" head "of the B2 primary winding L2, the audio signal from the remaining two head E, F input .
The "tail" of the secondary L2 connects L5 "head"; L2 "head" (M point) picks up the BG1 base; the "tail" of L3 "head", "tail" (P point) of L6 BG2 base.
Debug: When the circuit is connected to the right, turn on the power, adjust the R1, R2 resistance, so that the static current of BG1 and BG2 is 15mA.
Assembled: The left picture is the audio amplifier circuit of the Panda 805 electronic tube radio. When the "X" is disconnected, the B1, B2 primary E, and F access two breakpoints. At this time, the radio and power amplifier jointly synthesize a two-point frequency amplification system: the radiogram output transformer primary winding LO and capacitance CO constitute high frequency, medium frequency divider, direct push machine speakers to send trees and medium sound: low frequency part is large The inductance L1, L2 forms a pressure drop. After B1, B2 inverted phase, BG1, and BG2 are enlarged, and the speaker horn is pushed out.
The radio inside the radio tube 6H2 is an audio voltage amplification level; the tube 6H1 completes the treble, medium-sound power amplification, and completes bass promotion and inverting tasks; BG1, BG2 completes bass power amplification tasks.
After assembly, turn on the current, input from the pickup hole CK, you can audition.
Listen: High, medium, balance is very good, rich in musical details, high frequency soloction, clear whispers, bass shock, friends are very satisfied.
Component requirements: BG1, BG2 (all green dots) Strict pairing, each tube each uses 1 10 cmx25cmx0.3cm aluminum plate heat.
Power Transformer B: Wheneverally on the elongate silicon steel sheet having a thickness of 26 mm thickness of 26 mm, the primary φ0.51mm enamel wiring wrap around 1210 turns, the secondary φ2.0 mm enamel wiring wrap around 198 turns, tap, and power 100W.
Our other product:
