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.

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!

• Gain settings: MC (v lo)@: 72dB (+/- 1dB), MC (lo): 60dB (+/- 1dB), MC (hi): 48dB (+/- 1dB), MM: 36dB (+/- 1dB)
• AI Sub-sonic filter: Remedies only the 'warp' in LPs, no negative impact to bass response
• Max Output Voltage (RMS): 20v RMS bal output into 100k (< 1% THD+N), 13.5V RMS bal output into 600R (< 1% THD+N)
• Output Impedance: BAL: 200 Ohm resistive, SE: 100 Ohm resistive
• Input impedance: MM: 47K Ohms (Load: 110pF), MC High: 47K Ohms, MC Low: 1K Ohms, MC V Low: 110 Ohms
• SNR: 94dB(A) MM re 2V BAL/1V UNBAL, 80dB(unweighted 80kHz BW) MM re 2V BAL/1V UNBAL, 84dB(A) MC Hi re 2V BAL/1V UNBAL, 71dB(unweighted 80kHz BW) MM re 2V BAL/1V UNBAL, 90dB(A) MC lo re 2V BAL/1V UNBAL, 79dB(unweighted 80kHz BW) MC lo re 2V BAL/1V UNBAL, 79dB(A) MC vlo re 2V BAL/1V UNBAL, 69dB(unweighted 80kHz BW) MC vlo re 2V BAL/1V UNBAL
• EIN (equivalent input noise): 0.6nV|/Hz (unweighted) MC lo/vlo: -151dBV (A weighted), -141dBV (unweighted), 6.5nV|/Hz (unweighted) MM/MC hi: -130dBV (A weighted), -119dBV (unweighted)
• Harmonic Distortion: < -110dB / 0.0003% MM re 2V BAL/1V UNBAL, < -80dB / 0.01% MC lo re 2V BAL/1V UNBAL, < -86dB / 0.005% MC vlo re 2V BAL/1V UNBAL
• Power Supply: DC 5V / 500mA