Cookie-Cutter ‘Sub-Sonic Filter’

Tom Evans who makes very nice phono stages made the following astute comment:

A rumble filter simply adds to the bass cut making your already “cut” records sound bass light. Plus, it “time-steps” the bass in relation to the higher frequencies (where our hearing is most sensitive) so much so it can confuse the ear into believing the bass is playing out of tempo.

iFi solution:

Since the very first iPHONO launched in 2012, we have used our own in-house ‘Subsonic Filter’. It made it into the iPHONO2 and the iPHONO3 and now, the ZEN Phono which is the very first time this filter is seen in such an affordable price level.

As there is only minimal vertical modulation remaining at very low frequencies with an an actual cut LP that is playable, we know that “vertical modulation” at low frequencies must be warp.

So we designed a filter to take advantage of this.

This is not artificial but real knowledge. By understanding fully how LPs are cut and replayed,  it is possible to filter record warp strongly without at the same time attenuating low bass or adding group delay.

ZEN Phono
ZEN Phono
ZEN Phono — the ultra-affordable phono stage from iFi audio
Fall in love with your LPs all over again.

Pedigree. Performance. Peerless.

LPs + ZEN = Magical combo.

You’ve spent years building your dream LP collection. We know because we have done the same!

The ZEN Phono is a wonderful enhancement to your vinyl setup. It will max out every MM/MC cartridge.

Choc full of AMR/iFi trickle-down vinyl technology, it will have you poring over your LPs into the wee, small hours.

ZEN Phono — the ultra-affordable phono stage from iFi audio

Spec’d to make you smile

Unlike any other entry-level phono stage. The ZEN Phono has:

  • MM/MC from 36dB >72dB gain. Super-silent noise floor -151dBV
  • Precise RIAA with Balanced output, performance comparable to +$1k phono stages 
  • AI sub-sonic filter. Addresses warp without eliminating bass or causing phase issues

Hissless whisper

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.

ZEN Phono — the ultra-affordable phono stage from iFi audio

Mil-spec RIAA

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. Read more here.

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!

With great circuit comes great components

The ZEN Phono has some seriously good audio components backing up the fab circuit design which has trickled-down from its ultra-fidelity AMR PH-77 and iFi iPhono siblings.

Scroll down for more on the most consequential circuit highlights/boutique components.

ZEN Phono — the ultra-affordable phono stage from iFi audio

Super sub-sonic

The intelligent sub-sonic filter is from the iPhono range and is quite special.

Normal sub-sonic filters remove ‘rumble’ AND bass and cause phase issues.

Our unique AI phono sub-sonic filter removes ‘rumble’ only.

Majestic measurements

ZEN Phono: –151dBV
Stereophile Class A+ rated Phono: –131dBV

20dBV

quieter

With MM/MC, high/low and very low, the ZEN Phono is able to handle just about any cartridge. From 36dB all the way up to 72dB. So as your vinyl system grows over time, the ZEN Phono will always keep up.

Balanced circuit design. Just not seen at this price point it is a superior method to the traditional single-ended circuit approach. Balanced circuits reduce noise and crosstalk. Less Interference – clearer sound.

As with many other iFi audio products, we’ve incorporated a custom OV Series operational-amplifier. This top-notch component contributes to the extremely low noise, low distortion (0.0001%) and wide bandwidth.

Panasonic ECPU capacitors. Each ECPU capacitor is constructed from some 3,500 layers of ultra-thin dielectrics less than 0.5μm thickness. It offers class-leading Equivalent Series Resistance (ESR), low impedance and frequency stability and vanishingly low distortion.

Texas Instruments low-noise ICs offer great unity-gain bandwidth, very low noise and distortion, high output drive capability, Common-mode and Power Supply Rejection Ratios of over 100 dB, wide maximum-output-swing bandwidths and high slew rates.

TDK C0G (Class 1 ceramic) capacitors offer high stability and low losses for resonant circuit applications. They are pricey but are a perfect addition to our products.

muRata control-type, low-ESR high-Q multi-layer capacitors. The ‘ESR control’ aspect of the Murata is something special. Their noise suppression abilities are impressive.

Support

Gain settingsMC (v lo)@
MC (lo)
MC (hi)
MM
72dB (+/- 1dB)
60dB (+/- 1dB)
48dB (+/- 1dB)
36dB (+/- 1dB)
AI Sub-sonic filterRemedies only the 'warp' in LPsNo 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
SE
200 Ohm resistive
100 Ohm resistive
Input impedanceMM: 47K Ohms
MC High: 47K Ohms
MC Low: 1.4K Ohms
MC V Low: 110 Ohms
Signal/Noise Ratio: 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

6.5nV|/Hz (unweighted) MM/MC hi
-151dBV (A weighted)
-141dBV (unweighted)
-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
Dimensions158 x117 x35 mm
6.2" x 4.6" x 1.4"
Power Supply:DC 5V / 500mA
Net weight:515g (1.14 Ibs)
Warranty:12 months

Reviews

Review: iFi Audio ZEN Phono

“The main job of a phono pre-amp is to amplify the phono signal as per the RIAA EQ curve, in as clean and neutral way as possible in my opinion. The Zen phono nails it in that respect, vinyl playback in my system is immensely enjoyable with the Zen phono effortlessly amplifying everything evenly with a clean background. It is controlled and measured yet perfectly balanced, allowing you to enjoy the music as it was intended.”

Read more…

(Click name to read original review)
Menu