LUXKIT A1020
¥ 62,500 (released in March 1973)
Commentary
This tube pre-main amplifier kit not only has good performance but also takes design into consideration.
A 3-pole tube is used for the whole amplifier.
A 2-stage P-K / NF type equalizer, a 1-stage P-G / NF type buffer, and a LUX type NF type tone control are used. A total of four 12AX7 amplifiers are used for the preamplifier.
The output stage of the main amplifier section combines 6RA8, a 3-pole output tube with low internal resistance and excellent low-frequency characteristics, with an OY14 output transformer that exhibits excellent characteristics over the entire band.
The circuit that drives this stage employs a cathode coupled circuit called the Mulard type, which has a small time constant in the low-frequency range and is more stable and has a high gain.
The first stage is 6AQ8, and the phase inversion stage is 12AU7.
The external design is combined with the 500 series transistor-type pre-main amplifier.
The headphone port uses a headphone plug to switch the output of the main amplifier.
In the case of the kit, there is a problem of adjustment, but we have succeeded in drawing out the desired performance with minimum adjustment in the main amplifier and no adjustment in the preamplifier by devising mechanical aspects such as accuracy of parts and use of a board.
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Circuit diagram A shows the commonly used 2-stage P-K / NF type equalizer circuit, and circuit diagram B shows the equalizer circuit adopted for A1020.
For the circuit used in A1020, R2Is V2Plate to V1This resistor is connected directly to the cathode of the circuit diagram A.1However, in Schematic B, the low-frequency time constant is reduced by one step compared to Schematic A, and the phase characteristic is improved..jpg)
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The high-cut and low-cut filters use a circuit called the CR1-stage circuit. In the A1020, the low-cut frequency is 35 Hz and the high-cut frequency is 11 kHz as the standard. You can change the cut-off frequency by changing each filter capacitor in this circuit one by one.
Similarly, the standard low-frequency and high-frequency turn-over frequencies of the tone control circuit can be changed by changing the corresponding capacitor.
These changes are detailed in the Assembly Manual.
Model Rating
| Type | Tube type pre-main amplifier kit |
| Continuous effective output | 10W + 10W (4 ω, 8 ω, 16 ω) |
| Total harmonic distortion factor | 1% or Less (Rated Output) |
| Frequency characteristic | 20 Hz to 20 kHz - within 1 dB |
| Input Sensitivity / Impedance | Phono1, 2 : 2mV/47k Ω Aux1, 2, 3 : 140mV/150k Ω |
| Signal-to-noise ratio (input short, uncorrected) | Phono : 60 dB or more Aux : 77 dB or more |
| RIAA deviation | Within ± 0.5 dB (30 Hz to 15 kHz) |
| Tone control | LUX System NF Type Low-pass curve point : 250 Hz High-frequency curve point : 5 kHz |
| Filter | Low-cut : 35 Hz, -6dB/oct. High Cut : 11 kHz, -6dB/oct. |
| Attenuator | -14dB |
| Output voltage | Rec out:140mV Pre-out : 1 v (rated) |
| Attachment | Headphone jack Tape Monitor Switch (2 systems) Recording output terminal (2 systems) Preamp and main amplifier separable |
| Vacuum tube used | 6RA8 : 4 pieces 6AQ8 : 1 12AU7 : 2 Pieces 12AX7 : 4 Pieces |
| Semiconductor used | SD-1B : 4 S1RB-40 : 1 |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 150W at maximum output |
| External dimensions | Width 450x Height 160x Depth 330 mm |
| Weight | 13.3kg |