OVERVIEW
The design of this kit is with referenced to the classical McIntosh C22 pre-amplifier. It use ac-coupled high-ended WIMA MKP10 capacitor with tube pre-amplifier using 3 Shuguang 12AX7 tubes. High Voltage rectifier circuit use Vishay 1N5062 as bridge for full- wave rectifier.The power regulated by using a 6BM8/ECL82/6F3 Pentode-triode tube that provides power regulation and is resulted ~300V DC for later stage amplifying circuitry. A low dropout regulator LM1084 is used to supply the filament.
As all resistors and capacitors are low-noise with good channel matching, the sound quality should have low distortion.
FEATURES
The design of this kit is with referenced to the classical McIntosh C22 pre-amplifier. It use ac-coupled high-ended WIMA MKP10 capacitor with tube pre-amplifier using 3 Shuguang 12AX7 tubes. High Voltage rectifier circuit use Vishay 1N5062 as bridge for full- wave rectifier.The power regulated by using a 6BM8/ECL82/6F3 Pentode-triode tube that provides power regulation and is resulted ~300V DC for later stage amplifying circuitry. A low dropout regulator LM1084 is used to supply the filament.
As all resistors and capacitors are low-noise with good channel matching, the sound quality should have low distortion.
FEATURES
1. Use of WIMA, Japanese Nichicon, Rubycon capactors and Dale resistors.
2. Shuguang 12AU7 x3
3. Russian 6F3P (6BM8/ECL82)
4. PCB thickness: 2.5mm, double layer, 2oz copper.
5. Built-in rectifying circuits.
6. Separation PCB design of ground and supply voltage between main circuit block and power supply unit.
7. High dynamic range, output voltage can > 40Vrms.
FEEDBACK
1. Do not use hands or any body part to touch the board after power off, since the high voltage capacitor may not fully discharge.
2. Turn off the power supply if there are smokes, heat or sound given from the transformer.
3. Adding fuse to the transformer or any power supply source.
ASSEMBLY PROCEDURES
1. Download the schematic and BOM
2. Soldering all the components according to the BOM, notice to the polarity of the high voltage capacitors and the direction of the Zener diodes.
3. Either connect delay output protection kit (optional) to the jumper J6 and J7 or short it.
4. Connect the power transformer 280-300V AC and 12-15V AC to the board, without plugging the vacuum tubes.
5. Check the AC voltages at the connector to see whether the voltages are maintained, like 280V AC and 15V AC.
6. If everything ok, no smoke and no heat of the heat of the power transformer, plug back the vacuum tubes.
7. Re-do again step 5.
TEST RESULTS
Yellow traces are the input signal
Blue traces are the output signal
Input signal: sinewave at 100Hz
Input signal: sinewave at 1kHz
Input signal: sinewave at 10kHz
Input signal: sinewave at 20kHz
Input signal: square wave at 1kHz
FEEDBACK
By Steven Ho (Singapore):PRECAUTION
It sound very musical, detailed. Staging and separation are excellent. Bass is not dragging.
1. Do not use hands or any body part to touch the board after power off, since the high voltage capacitor may not fully discharge.
2. Turn off the power supply if there are smokes, heat or sound given from the transformer.
3. Adding fuse to the transformer or any power supply source.
ASSEMBLY PROCEDURES
1. Download the schematic and BOM
2. Soldering all the components according to the BOM, notice to the polarity of the high voltage capacitors and the direction of the Zener diodes.
3. Either connect delay output protection kit (optional) to the jumper J6 and J7 or short it.
4. Connect the power transformer 280-300V AC and 12-15V AC to the board, without plugging the vacuum tubes.
5. Check the AC voltages at the connector to see whether the voltages are maintained, like 280V AC and 15V AC.
6. If everything ok, no smoke and no heat of the heat of the power transformer, plug back the vacuum tubes.
7. Re-do again step 5.
TEST RESULTS
Yellow traces are the input signal
Blue traces are the output signal
Input signal: sinewave at 100Hz
Input signal: sinewave at 1kHz
Input signal: sinewave at 10kHz
Input signal: sinewave at 20kHz
Input signal: square wave at 1kHz
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