Stemming from the R&D work into the development of the micro iTUBE, the NOS6922 matched tube pair is another ‘atypical’ product from iFi that significantly improves the audio experience. For any tube/valve audio product from amplifiers to CD players

iFi Audio NOS 6922 Valves

Rating:
5/5,
  • From NOS General Electric 5670 tube/valve​

    The 6922 tube/valve is one of the most famous ‘dual triode’ designs and is ubiquitous. It has and is still, used in many tube/valve audio products from CD players to headphone amplifiers.​
    First introduced by Western Electric in 1946 with the WE396A, from the 1950s onwards (and for the next 30 years thereafter) General Electric (and several other tube/valve manufacturers) followed Western Electric with their own premium version of 6922. This range had controlled warm-up and tight specifications on grid-current, noise and microphony. The result, significantly smoother and more organic sound qualities.​
    While the 9-pin design was used, the electrical pin outs changed. As such, the GE5670 was not a straight ‘drop-in’ substitute for the 6922. So the GE5670 remain unloved and unused until……2014​

    From Machine-fabricated adapter with noise filtration​

    …2014, when iFi brought out the iTUBE tube buffer/pre-amplifier. From our research of the tube inventories around the globe, we found the GE5670 to be in supply and with surprisingly good sound. While the iTUBE was designed from day one with the GE5670 in mind, we found that customers really liked the GE5670 in the iTUBE but they wanted more…yet because of the different electrical pin configuration, the GE5670 was a no go.​
    The iFi solution was to machine-fabricate a special ceramic adapter with a miniature capacitor circuit to bring heater supply circuit noise (a common issue) sharply down.​

    Enter the NOS 6922 matched pair​

    Factory installed, the GE5670 + Adapter work as one (they cannot and should not be separated under any circumstances). Serendipity struck as the shorter GE5670 plus the taller adapter equated to virtually the same height (tolerance within ~1mm from tube to tube).​
    Therefore, there should be no physical limitations to installing the NOS 6922 tube set in any 6922 audio component.*​

    Special rejuvenation process​

    General Electric manufactured the GE5670 from the 1950s through to the 1980s. Hence each valve is at least 30 years old or more. This extensive length of time in storage means one should adopt a special temperature and time-controlled oven ‘baking’ procedure to gently ‘rejuvenate’ each and every valve.​
    If they were just powered up after such a long time in storage, it would certainly weaken their internal architecture and shorten the life span.​
    With iFi’s special rejuvenation process, we gradually bring the GE5670 back to life to continue the NOS military level of performance.​

    Hand-selected and computer-matched​

    At iFi, given the AMR background, we are literally besotted about tubes/valves. Therefore, we hand-select each and inspect every valve, to ensure their internal structure has not been compromised by the long storage. We then burn them in for 48 hours before finally matching them by computer.​
    This ensures that each and every pair is perfectly matched and prepared for hours of usage.​
    User Note* In rare circumstances, the iFi GE5670 tube set may not be a suitable replacement for the 6922 valve. No damage should result but when replacing the valve, as always, check that this does not void your product warranty. AMR/iFi is not responsible for any damage/injury caused.

    If in doubt, consult your product manufacturer prior to change the tubes/valves.

Recent Reviews

  1. ostewart
    Clean and Clear valves
    Written by ostewart
    Published Jul 22, 2017
    5.0/5,
    Pros - Detailed, fairly neutral for valves
    Firstly I would like to thank Karina at iFi for these tubes to review, as always I try to write honest reviews. These tubes have had over 50hrs of burn-in.

    Gear Used: Opus #2 > Feliks Audio Espressivo > Grado SR60e / Sennheiser HD650

    [​IMG]

    Tech specs and info:
    http://ifi-audio.com/portfolio-view/accessory-nos-6922-2/

    Packaging and Use:
    These are actually 5670 tubes in adaptors for use in 6922 sockets, and they come packaged in the usual slim white box from iFi audio. The box is understated and I appreciate the slim packaging, the tubes are carefully held in a foam insert to help protect them during shipping. They come with a pair of white cotton gloves to reduce oils from your skin contaminating the tubes. Overall a well packaged product which is kept perfectly safe during shipping.

    [​IMG]

    These 5670 tubes in adaptors can be used in the majority of amps that use 6922 tubes, and are for the most part a drop in replacement. iFi audio state that the tubes have been through a rejuvenation procedure of gentle heating up, and are not to be removed from the included ceramic adaptors.

    [​IMG]

    Sound:
    The reason I wanted to try these is that I like the original tubes that came with my Feliks Espressivo amp but tube rolling is addictive and I went down the rabbit hole. I am using 6N6P-I power tubes and went through some NOS Voskhod tubes that were great for warming up the sound of harsher headphones but lack top end detail. After that I invested in some NOS Tesla gold pin valves, which have an incredibly lush and slightly forward midrange but again were lacking finer detail.

    I have always been a fan of iFi audio products and their tube stages in the iTube and Pro iCan all use the 5670 and have incredible detail with a slight hint of tube lushness. I am not after a solid state sounding tube amp, but one that has a hint of tube warmth whilst still letting the details through.
    The iFi Jan 5670 deliver, and are in line with what I want, the first time I listened I was impressed, the highs that I was missing are back but still without glare. The bottom end is still wonderfully textured and full bodied; the mid range has an intimacy that is lacking with some more reference sounding amps. The highs come through with excellent detail that is lacking in some tube combinations.

    Now I know the tube amp output impedance isn’t always going to play nice with the low impedance Grado SR60e, but I have found with this pairing I am finding the bloat that occurred with other tubes has lowered, and the highs that were missing (I know, highs from a Grado not being bright?) came back.

    With the HD650 I always find their top end lacking too, and this combination is not going to make them treble monsters, but it does bring out some nice energy up top, yet again without harshness or metallic tone.

    [​IMG]

    Conclusion: In my opinion these tubes have made my Feliks Audio Espressivo an excellent performer for the price, and these tubes offer what I would call a more neutral sound than some other NOS tubes out there, but they still have that bit of tube warmth. They don’t make the sound bloated, they don’t make the sound congested, they are a clear and detailed sounding. Again I cannot state enough that tube rolling is all about creating synergy between your gear, if you feel like details are smoothed over with your current 6922 tubes, give these a try, for me personally these deliver the details I crave without brightness or unnatural tone.

    Sound Perfection Rating: 8/10 (you can get the tubes and adaptors separately for less, but at risk of not having matching pairs, and without knowing they are genuine)

    [​IMG]
      svetlyo likes this.

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