The old version of the phono preamp uses three 2SC1845 transistors, while the upgraded version has been added with three more transistors. Doubling the number of low-noise transistors in parallel further reduces noise levels, lowers input impedance, improves thermal distribution and stability, thus improving overall performance.
Overall Evaluation of the RIAA Preamp's Performance
Here's a compiled summary of the key results:
1. Noise Figure (N+D =Left Ch -82.4 dBr , Right Ch -81.6 dBr )
2. Total Harmonic Distortion (THD =Left Ch -84.1 dB / 0.00622% , Right Ch -83.3 dB / 0.00681% )
3. Total Harmonic Distortion + Noise (Left Ch -80.8 dB / 0.00912% , Right Ch -79.9 dB / 0.01006%)
4. Signal-to-Noise Ratio (SNR Lch: 86.7 dB / Rch: 85.4 dB)
Overall Verdict
The upgraded preamp shows exceptional noise rejection and channel balance. The aluminum enclosure optimizes EMI shielding, while the additional low-noise transistors in parallel further improves overall performance.
During music listening tests, we achieved an audibly silent background with vinyl playback. A quick check: with the volume control at mid position -lift the tonearm . This is where you'll hear impressively silent output from the loudspeakers, free from EMI or the buzzing 60Hz hum. Such performance can only be achieved by upgrading an already well-performing, sensitive RIAA phono preamp.