Circuit Features
Based on the core RCA amplification circuit of the Accuphase flagship C3850 preamplifier.
Design sourced from the international DiyAudio forum.
High Performance: Ultra-low distortion, ultra-low noise, very high signal-to-noise ratio, extremely flat bandwidth.
Dual-channel module design.
Compact structure, includes onboard rectification and filtering power supply.
Fully DC-coupled circuit – no input, output, or decoupling capacitors in the signal path.
Construction & Components
All new components used.
Audiophile-grade TI NE5534 single op-amps.
Philips audiophile-grade 'Silver Face' BC transistors.
KOA high-quality resistors.
WIMA high-precision capacitors.
ELNA power supply decoupling capacitors.
High-quality printed circuit board.
Assembled using American ALPHA solder wire.
Specifications & Parameters
PCB Dimensions: 100mm × 83mm
Operating Power Supply: AC 12V to 18V (AC 15V recommended)
AP Measured Performance (This Version)
Measured data is excellent.
Undistorted Output: 11.06V
Gain: 5.56x (14.9 dB)
Residual Noise: 4.47 µV (Low Noise)
Signal-to-Noise Ratio (SNR): 127.6 dB (High SNR)
Dynamic Range: 128.2 dB
THD: 0.000161% (Low Distortion)
THD+N: 0.000425%
Frequency Response Bandwidth: ±0.003 dB (Extremely Flat)
Every finished board is tested for distortion, noise, DC offset, and gain before shipment. Only boards passing QC are shipped.
C3850 Preamp AP Measurement Details
Test Equipment: APx525B Audio Analyzer
Test Power Supply: 15W "Bing Zi" brand transformer, ±15V supply
Test Date: October 16, 2025
Summary of AP Results:
Maximum output level as shown in the graph (implied).
Frequency Sweep: Very low distortion across the entire frequency band.
Very low distortion.
Extremely low noise.
Very high signal-to-noise ratio.
Very low intermodulation distortion.
Extremely flat bandwidth.
Low channel crosstalk.
Low channel phase difference.
