Flagship phono amplifiers create their own power supply off the mains, like a mains regenerator. This is fundamental to a well-designed phono stage. Without this, it will struggle to amplify the signal without added noise. This is why phono stages ‘hiss’ so annoyingly.
Unusually, the ZEN Phono has its own high-tech clean power supply. It creates a 1.2MHz power supply (20,000x mains frequency of 60Hz). In this circuit, a 10uF filtering capacitor = 200,000uF at lower, audible frequencies. With serious levels of noise filtration, it performs at the level of well-designed LC filtering circuits as found in classic tube amplifiers. Further, located on its own ‘island’ PCB, it is isolated so there is no noise pollution of the analogue stage.
Just super clean +/- 12V DC.
Measured EIN (Equivalent Input Noise) is -151dBV. It is 20dBV quieter than some Stereophile Class A+ phonos which are -131dBV.
The EQ circuit uses multiple TDK C0G capacitors in parallel. This is for best stability and the least distortion. They beat polystyrene capacitors and are close to Teflon.
Already using the lowest tolerance capacitors combined with multiples in parallel, tolerance is exponentially improved by the square root of the number of capacitors. This is quite a natty circuit design.
The RIAA EQ tolerance level (+/- 0.15dB) is impressive as it is en par with hand-selected capacitors!