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 that use the common 6922 tube/valve, the premium NOS 6922 matched pair set is a straight 'drop-in' replacement.

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.

Specifications:

What's in the box?

• User Manual
• STS Card