Discussion in 'Product Announcements' started by iFi audio, Aug 31, 2020.
I'll leave this here for now
ZEN gets groovy with iFi’s new phono stage
Adjustable gain? Tick. Subsonic filter? Tick. Class-leading, ultra-low-noise performance? Tick. The iFi ZEN Phono is an entry-level phono stage to surpass all others.
Southport, England – iFi continues to expand its multi-ward-winning ZEN series of affordable, desktop-sized audio devices with the ZEN Phono – a phono stage (or phono preamplifier, if you prefer) with a peerless performance at just £149, (€159. US$149).
iFi’s pedigree in phono stage design is considerable. The company’s recently launched flagship model, the iPhono3 Black Label, delivers class-leading, ultra-low-noise performance at £999, while the PH-77 from iFi’s sister-company AMR is a £12,000 reference-class phono preamplifier. The ZEN Phono is the first sub-£200 phono stage iFi has made and in terms of sound-per-pound performance it is a truly remarkable device.
For anyone diving headlong into the vinyl revival, the ZEN Phono is the ideal companion for their chosen turntable. It delivers a specification and performance unparalleled at the price, able to match perfectly will all manner of phono cartridges, whether moving magnet or moving coil.
Take the stage
Every turntable needs a phono stage to amplify the low-level output from a phono cartridge to ‘line level’ and apply RIAA equalisation. Some integrated amps and preamps have phono stages built in, but these vary in quality and are rarely as good as a well-designed offboard phono stage placed in the signal chain between the turntable and a line-level input on the amp.
Designing a truly high-performance phono stage is not an easy thing to do. For one thing, it is difficult to amplify the delicate output from a phono cartridge without also amplifying noise. In addition, the wide variation in output from different cartridges means that many phono stages only work optimally with certain cartridge types. These issues are exacerbated at the entry-level end of the phono stage market, where basic circuit design using common off-the-shelf components often leads to a performance that is adequate at best – okay for entry level, but easily outclassed by spending more.
The ZEN Phono’s discrete, balanced, dual-mono circuit design is unique at the price
The ZEN Phono has been designed to push the boundaries of what can be achieved in an entry-level phono stage. Its circuit design is like nothing else at the price, with a range of precisely engineered settings that ensure genuine versatility. Whatever the turntable, whatever the cartridge, the ZEN Phono always delivers a class-leading performance.
A question of balance
The ZEN Phono’s circuitry is of balanced, symmetrical dual-mono design – a topology usually reserved for high-end audio products owing to complexity and cost. Balanced circuit design has the ability the reduce noise and crosstalk, thus increasing sonic clarity, and has long been championed by renowned high-end audio electronics engineer John Curl – a man whose analogue amp designs, including several landmark phono stages, have been lauded since the 1970s.
Curl, now a technical consultant for iFi, has worked with iFi’s in-house technical team, headed by Thorsten Loesch, to produce a circuit design of exceptional quality for such an affordable phono stage. A fully balanced, ultra-low-noise design of this kind is unprecedented at such a low price point.
Sum of the parts
The ZEN Phono’s balanced circuitry contains surface-mounted components of unusual quality in an entry-level design. For example, the capacitors used include TDK C0G and Murata multilayer ceramic types, as well as Panasonic ECPU polyphenylene sulphide film devices – none of these are cheap, but their class-leading ESL (Equivalent Series Resistance) and individual qualities such as high stability and low distortion pay great dividends in terms of sound quality and the accuracy of RIAA equalisation.
In common with many iFi audio products, the ZEN Phono incorporates a custom OV Series op-amp – in this case, the OVA2637. This also contributes greatly to the price-busting audio performance, thanks to ultra-low distortion (0.0001%).
The best phono stages on the market create their own power supply off the mains, similar to a mains regenerator, in order to amplify the audio signal from the cartridge without adding noise. The ZEN Phono achieves this aim, but not in a conventional way; it creates a power supply with an oscillation frequency of 1.2MHz, which is 20,000 times that of mains electricity. In this circuit, a filtering capacitor with a 10uF rating is equivalent to 200,000uF at lower, audible frequencies – exceptional filtering power. The power supply circuitry is located on its own ‘island’ on the circuit board to ensure there is no contamination of the audio signal – just super-clean +/-12V DC.
The ZEN Phono’s front panel sports a ‘subsonic filter’ button, as well as LEDs to indicate the selected gain setting
High-end features, entry-level price
Phono cartridges vary greatly in their technical characteristics, but few sub-£200 phono stages handle moving coil (MC) cartridges in addition to moving magnet (MM) types, let alone offer further gain adjustment to make the most of whichever MC cartridge the user chooses to employ.
The ZEN Phono is the exception, delivering a range of gain settings from 36dB to 72dB – impressive even in a much more expensive phono stage. There are four gain settings in total: 36dB (MM), 48dB (high-output MC), 60dB (low-output MC) and 72dB (very-low-output MC). This enables the ZEN Phono to take even the more exotic MC cartridge types in its stride.
Another rarity at this price level is a subsonic filter, engaged via a front-panel button to tackle the large subsonic signal output caused by warped records. A feature of all iFi phono stages, this proprietary circuit ‘intelligently’ filters out the unwanted subsonic output without affecting any deep bass on the recording – an undesirable side effect of some warp filters.
Around the back reside stereo RCA inputs/outputs, a 4.4mm Pentaconn balanced output, a grounding terminal and the gain selector switch
This is how it works: vinyl cutting lathes incorporate a so-called ‘elliptical filter’, which means that low-level bass on an LP is invariably mono and creates only horizontal movement of the stylus. Therefore, any low-frequency vertical movement of the stylus as it tracks the LP can only be the result of record warp. iFi’s subsonic filter removes the effect of record warp from the vertical plane, doing its job efficiently without the common drawbacks of attenuating any low bass or adding group delay.
Ins and outs
As well as the usual stereo RCA inputs and outputs, gold-plated for optimal signal integrity, the ZEN Phono’s rear sports another phono stage rarity – a 4.4mm Pentaconn balanced output. This can be used to connect to an amp or active speakers equipped with a balanced input – either a Pentaconn 4.4mm input, such as the one found on the ZEN CAN analogue headphone amp, or XLR inputs via an adapter. This enables a fully balanced connection that makes the most of the ZEN Phono’s balanced circuitry – no other phono stage at this price level offers a balanced output option.
A grounding terminal is also provided; attach a turntable’s grounding wire to this to avoid ground loop issues that can cause an audible hum. Even the way the ZEN Phono switches between settings has been engineered to ensure sonic transparency, handled by a microcontroller that only ‘wakes up’ when a setting is changed to avoid any sonically deleterious electronic noise.
Find your ZEN
The ZEN Phono is the fourth product to join iFi’s ZEN Series – a range with a mission to make high-performance audio more accessible than ever. Just like the ZEN DAC, ZEN Blue and ZEN CAN, it delivers a level of specification and performance never before seen – or heard – at its price point. The iFi ZEN Phono is available from selected retailers from 4 September, priced at £149 (€159, US$149).
The ZEN Phono can connect to the ZEN CAN to make a fantastic vinyl headphone system with balanced connectivity
@iFi audio - do the gain switches also change input impedance? I don't see any info in the specs.
@purr1n - cheap phono stage comparo (vs TC750 and whatever else you have around)?
Most likely not but I'll ask internally to double-check.
In the meantime...
Any update on this?
Answering my own question: input impedances are now listed on the specs tab of the product page:
MM (36 dB gain): 47k Ohms
MC High (48 dB gain): 47k Ohms
MC Low (60 dB gain) 1.4k Ohms
MC Very Low (72 dB gain): 110 Ohms.
Natural competitors around this price ($149) and with similar specs would be the $129 Schiit Mani
with 4 gain settings and 2 input loadings (47k & 47) that are selectable independent of the gain setting; and the $189 Hagerman Bugle 3
with 4 gain/load settings.
I got this in. Review forthcoming, This is an utterly insane value and basically crushes everything in the price range and even way up to $1000. (Yes, "value" in the TT world is generally shit).
Not sure why, but I dig this post
totally OT, but a review of the ifi retro stereo 50 would be incredible. maybe ifi audio can ship you a unit for review?
WTH? Holy cow! That actually looks kind of cool and the price... wut? That's just slightly more than a pair of crappy "hi-end" self-powered monitors. Maybe the receiver for the loaner program. I know lots of us have decent HE speakers already. Ahh, tone controls FTW!
@iFi audio can you guys add a 'no BS' section to your site so people with a modicum of electronics knowledge can find out WTF is inside the product instead of reading marketing copy?
I had to google around to find out what tubes the stereo 50 uses. it looks like push-pull EL84x output stage with ECF82 used as phase splitter/driver. I guess the phono stage is JFET? not even the manual has this information
is there a resistor network for the headphone output?
And it sounds great to boot, Ive sold my ifi Pro ican cause I preferred the Retro Stereo 50 or rather I didnt think the pro ican was worth keeping having just bought the Stereo 50. Ive sold my Audio note el84 L1 integrated amp as well once I compared to the Retro: they both sounded so close to each other to my ears in a blind test. The bass is decent but lacks that ultimate SS punch, the trade off is all the good things about tubes.
the dac is only decent, Its just a nice decent addition but it doesnt suit Utopia or HD800, for those i much prefer the EC Desing R2R dacs. but the dac accept wireless and I use the internal dac often as I dont really care about ultimate sq most of the time.
the included phono stage as far as I understand is a ifi iphono 1?
I havent upgraded the output caps yet (but ordered the mundorf 0.1uf for it) nor the pot (to alps blue), but I suspect it would kick this up a notch as well.
all in all, its a steal. Ive got mine for 1500$ CAD (1100 USD) brand new. The newer models have the removable upper grills for easy tube access.
lol, agreed. their marketing works for a certain section of audiophiles, but it smell and looks baloney for another segment of us.
have more info and decent pictures to see what's going on. very simple power amp section design
the head-amp is basically the power amp section with a resistor padding it down. depending on the tubes you use, its dead silent, or almost totally silent with some nos tubes. compared to the Vali og, Stereo 50 much more silent even with noisy tubes.
In my ifi retro stereo 50, I use NOS EL84 (you just can remove the jumpers to use EL84 rather then EL84X) and NOS ECF80/ECF82 for the driver.
EL84x: I wont say what it is but you can sort of read between the lines and figure it out which tube it actually is.
EDIT: my driver tube I use is NOS RCA 6U8A
I assume not fixed bias right? Won't be close to SS bass unless, but this does have its charms with a built in DAC, phonostage, and tone controls.
I figure the marketing angle is toward more normal folk and less audiophiles. Heck, the manual doesn't even have anything on tube rolling.
this is their tech notes: seem to answer your question and @k4rstar
"So, whereas a sine wave has a constant demand of power, music has a low average power requirement, but a high peak requirement. Both classic Tube Amplifiers as well as modern ones (like the Retro Stereo 50) often employ a method to control output stage quiescent current called variously self‐bias or cathode bias. This method has a great advantage in that it makes the resulting amplifier self‐adjusting, with no need to perform maintenance nor regularly adjust the tube bias. For a Push‐Pull Amplifier (such as the Retro Stereo 50) this means that if the Amplifier output stage is driven out of the Class A operation the bias voltage will change. In effect, the bias will increase thus turning the output tube off progressively. Another mechanism is the onset of so‐called ‘grid current’ which creates an additional negative grid bias; again, in effect turning the output tube more off, when it should be turned more on. There is timing linked to this. In the Retro Stereo 50 for example, the cathode circuit will delay this self‐adjustment by around 0.2 seconds (the grid circuit even longer), long enough to deal with largely all musical peaks, but so short that with steady state sine waves the adjustment seems instant to the experimenter or audio test set. The result, using sine waves, the amplifier seems to ‘saturate’ at fairly low power, turning up the input signal produces more distortion but no more output. In effect the amplifier power with steady sine waves is self‐limiting, yet the limits do not apply to short high‐power events.
This particular mechanism was well known in the ‘Golden years’ of tube audio and widely discussed6. It was also widely known that optimising an Amplifier output stage for sine wave testing would increase distortion with music or speech signals7. Equally known and discussed was the fact that sine wave measurements were not representative of the maximum power output available from a Tube Amplifier playing music into speakers"
self-bias and from what I understand, the amp stays in Class A operation with headphones and very efficient speakers
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