Apos Ray 12AU7 Vacuum Tube


Headphoneus Supremus
Best among new production tubes!
Pros: - excellent sound quality
- extremely low noise floor
- great bass extension and quantity
- enchanting mids
- extended but not overly bright treble
- slightly warm tilt
Cons: - price
- unavailable outside of the US
During a recent tour initiated by @Deleeh, I had the unique opportunity to experience the Apos Ray 12AU7 tube, which is a very new entry among new production tubes. It's important to note that I have no affiliations with the manufacturer, ensuring an unbiased review of this product. I didn't even have direct contact with Apos staff, as Deleeh managed everything regarding tour logistics. Luckily I am last in the tour and have had extensive amount of time to test and enjoy them. (roughly a month at this point)

One of the first things that strikes you about this 12AU7 tube is its packaging. Unlike the standard presentation you might expect from 12au7 vacuum tubes, this one comes extraordinarily well packaged. It's clear that the manufacturer aims to deliver a high end product, starting with the unboxing experience.

Front and Back print

Stacked on adapters

Before diving into the sonic qualities, it's worth mentioning the price point. The Apos Ray 12AU7 tube sits at the higher end of the market at 180$ for the matched pair. This might give pause to some potential users, but as we'll explore, the quality and performance may justify the investment for serious audiophiles. At the time of writing this review, the tubes are only available within the US, with no offers in europe.

The setup used for this Review is the well regarded Feliks Envy 300B flagship amplifier. Power tubes used are the Elrog ER300B and in order to use the Apos Ray 12au7, an adapter is required, since the amplifier runs natively with 6SN7 tubes.
Both tube types can be used in the same circuit, since required voltage and amperage are the same, just the socket needs an adapter.
DAC used is the T+A MP2000R and the Source is a Rockna Wavelight Server running Roon with lots of local flac files and Tidal.
Aesthetically some Mini Elrogs paired with big Elrogs


Sound Quality:

When it comes to bass, the 12AU7 tube impresses with its extension and solidity. The bass notes are not just heard; they're felt, providing a robust foundation that's neither overpowering nor underwhelming. It's a delicate balance that this tube manages to achieve, offering a satisfying quantity of bass that complements a wide range of music genres.
As a Basshead I instantly fell in love with the Rays 12au7s presentation of that aspect.

The midrange is where the Ray 12AU7 offers a sweetness that's hard to come by, making vocal tracks particularly enchanting. Instruments have a natural warmth and presence, making each note distinct and full of emotion.

In the High frequencies there's no harshness or sibilance, just smooth, refined highs that extend well, adding sparkle and detail to the music. This silky quality ensures that even after extended listening sessions, listener fatigue is minimal, if present at all.

Compared to all the 6SN7 counterparts that I usually use in my amplifier, the soundstage is more intimate on the Ray 12au7. Instrument placement and separation remains excellent, even though the room size feels smaller than on Linlai E-6SN7 Elite for isntance.

In terms of detail the Ray 12au7 also absolutely delivers. Even finest nuances can be heard very well, which certainly partially depends on the extraordinarily low noise floor, that this tube provides.

Over the full frequency spectrum the Apos Ray 12au7 is mostly neutral with a slight tilt towards the warm side.

In conclusion, the Apos Ray12AU7 offers a compelling auditory experience that justifies its premium packaging and price. Its ability to deliver extended and solid bass, sweet mids, and silky highs makes it a standout choice for those seeking to elevate their audio setup without the hassle of hunting for NOS tubes. Whether you're an audiophile or a music enthusiast looking for quality, the Apos Ray 12AU7 tube deserves your attention.

I personally will add these to my collection after the review tour is over. I'm also looking forward to further tube releases of Apos Audio, they are certainly on my radar now, after this excellent first release.
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Wonderfull and Thank You,🙏🙏🙏🙏🙏🙏.

Thanawit Sagulthang

New Head-Fier
Apos Ray 12au7- Fantastic all-rounder with no major flaw. Will give many cheaper tubes a KNOCKOUT!
Pros: -Warm and Linear Tonality
-Even Presentation
-Excellent Separation
-Extra Sense of space
-Okay Dynamic
-Excellent Timbre
-Low Noise floor
-Immune to EMI
-No major-sound-detriment in any category
Cons: -Poor quality shipment through Amazon
-Extra import fee, depending on country, if purchase through Amazon
Disclaimer: The Apos Ray tubes are purchased with my own money. No one is paying or telling me what to say, all thoughts and opinions are my own.


The Apos Ray tubes were ordered from Apos shop through Amazon. I removed one star because of the damaged packaging. The tubes come in an Apos box which is shipped within a thin plastic sleeve. There is no use of cardboard box or extra bubble wrap to protect the Apos box, as a result through shipment the box got crushed and damaged. Luckily the tubes were intact, however, this is unacceptable as a standard shipping procedure. I order this product from America, and it is shipped to Thailand more protection should be given to product that is shipped internationally. $40 extra is paid for the import fee.

Pic. Damaged Apos ray box (top), Thin plastic cover it is shipped in (bottom).

0. The Context of this Review

0.1 Source Chain

While listening with Ray tubes, I discovered that the sound continues to change up to 20 hours of burn in. Hence, this review is a sound review after 20 hours of use. I listen to music at around 80dB on average. My source chain is Clef power bridge duo (power regulator), Asus laptop (source), Ifi micro idsd black label (digital to analog converter and pre amp), Cayin HA6A(amplifier)(with cage on): Power tubes: KT88 Full Music; Pre tube: Apos Ray; Rectifier tubes 22de4: NOS General Electric [GE], NOS Rca [RCA]. Hifiman Sundara (headphone). Audioquest, Furutech, and Cross Lambda cables.

For a better understanding of the context the reviewer is expressing, this is my opinion on the tonality of the gear I use in this review. Excluding the rectifier tubes in my system I considered my chain to have a relatively neutral tonality. Ifi micro idsd black label dac and preamp (dead neutral)(whisper “I acknowledge this device has a very warm power amplifier section”), Cayin HA6A amplifier (dead neutral), KT88 Full music tube (very slight warm), Hifiman Sundara (neutral, with a slight brightness at around 8kHz), GE tubes (very mid-range forward with bass roll off), RCA tubes (warm, with treble roll off).


Pic. Cayin HA6A with cage on and Hifiman Sundara (left). Cayin HA6A without cage (middle). Ifi micro idsd Black Label (right).

Pic. Kt 88 Full music tube (left). 22de4 rectifier tubes: top General electric, bottom RCA (right).

0.2 Music Taste

I mainly listen to dramatic instrumental music played by multiple instruments (60% Anime OST, 20% Movie and Games OST, 10% J-pop & J-rock, 10% others) Unfortunately there will be no vocal descriptions in this sound review.

The 10 tracks to give you a glimpse of what I listen to [song/album or anime/artist]

1. What is this thing call love/Bloom into you/Michiru Oshima
2. The Ultimate Price/Violet Evergarden: Automemories/Evan Call
3. BLEACH TYBW theme/TV animation bleach the blood warfare ost1/Shiro Sagisu
4. Journey of a Lifetime~ Frieren Main Theme/Frieren beyond the journeys end/Evan Call
5. Smash an enemy/One Punch Man/Makoto Miyazaki
6. Rapid as Wildfires/Genshin Impact/Yu-Peng Chen
7. Andor (Main Title Theme Ep1)/Andor Vol.1/Nicholas Britell
8. Rainy Night in Tallinn/Tenet/Ludwig Goransson
9. Ga1ahad and Scientific Witchery/Miracle Milk/Mili
10. The Theme from “Modern Juzz”/Modern Juzz/Ponta box

0.3 Description and Interpretation

It is important that I describe my experience as accurately as possible hence, I decided to divide the sound section into two parts. The first part talks about the characteristics of the Ray tube that can be easily noticed, not necessarily its stronger traits, but the characteristics that I find obvious and is the first thing that comes to my mind. The second parts talk about characters that may not be as noticeable at first, it does not jump out to scream at you what it is doing, but is important nonetheless. As for the degree to which the relative strength of each category is, I am deliberate with the terms I use and do not exaggerate my lexicon. If I say it is a “tad better” it is just slightly better, if I say the different is “noticeable” it is certainly easy to perceive that difference, if I say it is “night and day” the difference is enormous. With that said let the review begins!

0.4 Comparison

Others 12au7 tubes which will be used for comparison in this sound review.

1. New production JJ Tubes (came with the amplifier) [JJ]

2. New production Full Music $70 (per pair) [FM]

3. NOS Sylvania 6085 $70 (per pair) [Sylvania]

Pic. JJ, FM, Sylvania, and Apos Ray tubes.


In general, Ray tubes have a well-rounded sound, it keeps the instruments impressively well separated, has a slight warm and linear tone with no sibilant to be found, equipped with a classic increasing-space-from-tube plus some extra texture, topped off with great timbre and low noise floor. It received a 5/5 stars for sound.

1. The most noticeable characteristic of this tube

1.1 Warm and Linear Tonality

The first thing I noticed with the Ray was the shifted in tonality. If JJ tubes are considered to be dead neutral, Sylvania and Ray are slightly warm, while FM is warmer. The warm tone gives a relaxing cozy vibe to the music in addition with its good extension on both upper treble and sub bass, a healthy level of excitement is maintained throughout the listening session. Overall, the Ray has a very even frequency response with no apparent peak or dip at any particular frequency. This gives the Ray a smooth sound with no harshness left to be found. For context, I am sensitive to trebles and cannot tolerate bright headphones such as Hifiman Ananda or Hifiman Arya. The Hifiman Sundara that I use can be too bright for me if the source that I pair it with is too cold sounding. While using the Ray, the treble extension has good shimmer and sparkle but is never too bright or fatiguing to listen to. In comparison, I find the FM V-shape sound signature, containing a peak at around 8kHz, to be exhausting to listen to with certain genre. The opposite can be said with Sylvania, in which the frequency is rolled off at both extreme frequencies. The Ray contrasts other tubes as less enjoyable, from the too bright treble of FM to the lack luster sub bass of Sylvania.

1.2 Even Presentation / Excellent Separation / Tube Pairing

Ray tubes has an engaging sound that does capture your attention without ever sounding too forward or forced. It gives an even amount of body to each instrument, in contrast, Sylvania gives the band-leading-instrument more body, more forward (closer to you), and focus presentation than the rest of the band. The disproportionate body that the lead instrument received overshadows the rest of the instrument, hence separation suffers. Ray tubes, however, give an even amount of body to every instrument. When compared against Sylvania, the loudest sound becomes quieter, and the quietest sound becomes louder, resulting in better instrument separation. In fact, the Ray separation pulls a far lead over the second place, Sylvania, and a giant leap over FM and JJ.

For music with a busy passage with multiple instruments playing together, such as that in a symphony, the separation between each instrument can be heard effortlessly on the Ray. It is a joy to follow through different passages of melodic layer with the Ray, whereas, in a busy passage, no amount of attention given deliberately can ever differentiate certain music layers apart when listening with FM or JJ.

The Ray pairs better with tubes which have good focus and clarity such as GE. Unlike Sylvania, which pairs better with tubes that has a smoother and more laid-back presentation such as RCA. Pairing the Ray with the RCA (which has a laid-back presentation with treble roll off but is hazy/fussy/and has lower resolution) can be too much of a good thing. The combination gives extremely smooth fatigue free music, but the lack of resolution does make it sound bland and unengaging.

1.3 Extra Sense of space

Not every tube can give an extra sense of space around each instrument, but great tubes can, and Ray is one of them. Although Ray tubes have more sense of space than any other tubes that is in this comparison, it should be mentioned that “soundstage size” and “sense of space” are not the same thing. JJ and FM tubes have a small soundstage, the width of the stage in which the band is playing is small, while Sylvania and Ray have a larger soundstage. Even though Sylvania and Ray have a similar “soundstage width”, there is more “space” in between each instrument within that soundstage when listening with the Ray. This should be commended as Ray tubes do not achieve this presentation through an addition of excessive amount of treble frequency. If anything, the presentation sounds convincingly natural as if somehow more space is added to the recording. Sylvania sense-of-space, on the other hand, does not sound as large nor as natural. This is because that sense-of-space is created by adding a reverb-like effect to the instruments, hence the music can sometime sound slightly echoey. The sense of space is even more limited with the FM tubes and is nonexistent with the JJ.

2. Other Characteristics

2.1 Velvety Texture

If clean clear solid-state like presentation is what you are after, such as what found in JJ tubes, Ray tubes are not for you. The Ray adds a bit more texture to music to a similar degree to what Sylvania does (both less so than FM). This makes the sound of instruments decay and the material in which they are made of becomes more apparent. For instance, more body from violin can be heard when the bow moves against the string, drums leather fabric texture and its rumble can be heard more easily when it is hit with a stick. The effect is not overly done and does not make the music sound muddy.

2.2 More Than Acceptable Dynamic

The Ray dynamic is second only to the FM tubes, yet it is more than dynamic enough for me to feel whatever emotion the music is conveying. Orchestra do have a somewhat grand presentation with impactful and deep bass while retaining control. Dramatic feeling reaches the listener when there is a passage with big dynamic swing. The listener would never feel that the Ray is inhibiting the dynamic that the amplifier has to offer, but nor does it deliver the most out of the amp. Note that: dynamic is the trait that I value the most in my system hence being “good enough” to me is likely a “great” for others. FM tubes do bring a more grandiose presentation, more weight and impact, particularly at low frequency. The increase in dynamic switching from Ray to FM is very noticeable. If dynamic is the only trait that you are after, the Ray may not be the best tube for you.

2.3 Excellent Timbre

Ray tubes will show the listener what an excellent timbre sounds like. The instruments tone sounds correct, violin sounds like a violin and piano sounds like a piano, and their tonal color stands out. This is apparent particularly for music which uses real instruments. Each tone of the C D E F G notes that is played can be heard effortlessly and the music is filled with life and energy. The music which is highly melodic dependent that is played by real instruments such as violin and pianos will receive the biggest benefits, although other genres such as rock and metal do receive benefit as well. The Sylvania timbre, which I thought was excellent, is surpassed by a smidge by the Ray. While the dull sounding JJ and the metallic timbre FM sound night and day worse than the Ray.

2.4 Low Noise floor

Ray tubes have the lowest noise floor among the four 12au7 tubes. Having the least “hissing” sound in a listening-test in which the amplifier volume is maxed out when no music was being played. Ray tubes are also well protected from external electromagnetic interference, staying dead silent when phone calls are made 1 meter from the tube amplifier with its metal cage on. This is not the case for Sylvania, as it would make an audible winding noise every time a message is received on my mobile phone and makes a loud winding noise when there is a phone call.


Overall, Ray has many strengths from the sound to the user experience. It is a well-rounded tube with no major flaw in any category, while easily surpassing the performance of the other 3 tubes in most categories. The fact that the other tubes in this comparison always have an “if” or a “but” in certain categories proves just how difficult it is to design a well-rounded tube, in which the Ray is. If the Ray characteristic I aforementioned is to your interest, I highly recommend giving the Ray tubes a try. Although this is not a fair comparison, as I do not have a price appropriate or a more expensive tube to compare the Ray to, it does show that you do get more for what you paid for beyond the $70 mark.
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100+ Head-Fier
Apos Ray 12AU7 - A glowing light in the dark!
Pros: affordable 12AU7 tube
new production
balanced sound
Cons: not available outside USA

Disclaimer: The Apos Ray 12AU7 tubes were temporary provided as part of a European loaner tour

The new production Apos Ray 12AU7 tubes come in a very nice compact box with magnetic closure.
I connected them to the xDuoo TA-22 hybrid tube amplifier as soon as I received them (they had already been burned in by a previous reviewer).
After a bit of a warm-up on first listen, it was immediately clear that the sound of the Apos Ray 12AU7 tubes had gained in clarity and refinement compared to the xDuoo's stock tubes. Really a good upgrade for the xDuoo TA-22.


Balance In - Balance Out

The mid-bass has also gained in finesse, while being less bloomy with a slightly reduced quantity. Its really more balanced over all frequencies while still retaining the tubish qualities. This was also the case when using the Apos Ray with the Cayin HA-3A transformer-coupled tube amplifier (standard tubes from JJ Electronic), you give up some of the mid-bass elevation of the stock tubes for a more balanced approach with improved clarity - it's not less engaging, just a different flavor!



Headphones tried on the Apos Ray 12AU7
ZMF Caldera
ZMF Atrium Closed
Meze Liric
Denon AH-D9200
E-MU Teak
Klipsch HP-3
Dan Clark AEON 2 Closed
Kennerton Rögnir
Kennerton Rögnir Dynamic
Fostex TH-909
Audeze LCD-XC 2021

Gear used for comparison
xDuoo TA-22 [tube hybrid amplifier]
Cayin DAC 11 + Cayin HA-3A [Burr Brown DAC with tube output + transformer-coupled tube amplifier]

It is becoming increasingly difficult to find "new" old tubes at reasonable prices and with consistent quality.
With the Apos Ray 12AU7 you get a balanced tube sound at a high level at an affordable price.
I only wish they were also available outside the USA.
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Headphoneus Supremus
Monster of New Stock 12AU7
Pros: Sound
Very good workmanship
Modern packaging
Price definitely reasonable for what it offers.
Exactly what you expect from New Stock and what you get in the end.
Very strong on tube amps and better than expected.
Depending on the pairing, the golden ticket for the ears
Cons: Availability, at the point that you are working on making the tubes more accessible.
Currently, the additional import tax would still be worth the expense.
It was generally hard to find anything at all, my review will tell you something about it.
Can be not so strong on Hybrid amps but is a clear amp thing not a bad thing just a point of view.

I have had the privilege of testing your 12AU7 Ray tube with Apos Audio.
Many thanks at this point.
And also a big sorry that it took so long for the review from my side.
Life always plays tricks and it is always very difficult to get back to where you were in the end.
If private things come in between, like unexpected deaths in the family or Job things.

Foreword: I do not receive a fee or anything similar, this evaluation is based on a voluntary basis.
With other participants in Europe, Apos Audio provided us with the tube.
And I organised the tour.

Setup: The setup consists of the Gustard R26 Dac connected by the Singxer Su2 via I2S.
Headphones are mainly the Zmf Atrium and speakers from Elac from the 90s that have been refurbished.
The amplifier is the Mcchanson Ultimate, which is very special in its design and circuitry.
The amplifier can use 12xx7/6SN7/6SL7 as drivers, of course also several with appropriate adapters.
As output we have different possibilities, 6Y6 is the main driver at this point.
But others can be used like EL34,KT63,66,88,the whole 6x6 family like 6v6,6K6 as example and many more where adapters EL12,EL32,EL81,807 ect... are necessary.
The circuit is based on the builder hand soldered with point to point wiring, his experience is in this area also
He has a lot of knowledge from the old days, but nothing modern except the chosen components.
The 6BW4, EZ80/81 can be used as rectifiers, which have some influence on the final sound.

Forword II:
The actual story of how the test came about I'll tell you openly, I couldn't keep my mouth shut.
I watched the tests on Youtube from well-known reporters.
For the fact that you actually do this professionally, I expected more, but it's nothing personal at this point.
Much more a comment.
I think such a test with such tubes needs a serious amplifier, and not a hybrid amplifier, even if it is permissible.
Don't misunderstand, it certainly sounds very good on a hybrid, but you are also giving something away.
Even hybrid amplifiers should be well built if you want to be satisfied in the end.
They are also their own expense in the end.
Due to the diversity of the Mcchanson amplifier, i have stressed the 12AU7 well and I have also taken my time in the sessions to be able to judge many combinations.
And has also seen several 100h on it and runs here without problems.
I can tell you in advance that this tube does a very good job, especially on real amplifiers where the circuit was designed for it.
To the test itself, tubes need time, a lot of time until they are where they belong.
The 12AU7 Ray from APOS AUDIO has been in use for the last few weeks with various output tubes.
And in order to be objective enough to see how it performs in the long term, a combination was left in for 1-2 weeks or longer.
Also to hear how subtly things develop in the tube amplifier.
Here the 12AU7 Ray from APOS AUDIO never caused any problems and always sounded amazingly good, that much I can say.


We see grey plates with 2 holes on the outside top and bottom, the middle part is 2 ribbed.
Double Mica's, on top a Ufo getter with a chrome coating, the pins are gold plated if you follow them you will see copper inside which is connected to the construction on the inside.
connected to the construction on the inside.
Connoisseurs can already guess that the tonal orientation here tends towards the warm side and the construction looks very artificial.




Burn in and sound:
The12AU7 Ray from APOS AUDIO actually advertises a 6-hour burn-in time, which I paid particular attention to. And I have to agree at this point.
Forget the first 6-8 hours completely before you think about making a judgement, and a little more playing time won't do any harm.
It sounds a bit strangely unsorted at first and is no fun either.
Give the tubes time, it's a lot less than you're used to. I found after burn in it got slightly better after the first 50 hours.
And actually gets better over time with prolonged use.
The sound after burn in, well it has a basic tone that doesn't disappoint where.
It is warm, rich in detail, has a good sense of dynamics and focus.
Bass is very well dosed, the mids are very authentic and powerful, the treble range is very well resolved, free of peak as well as shrillness.
Depending on the output tube, you can steer the sound in the desired direction.

If you have the option of playing with the rectifier on your amplifier, go ahead, even if the influence can be marginal.
In the end, it can be the golden ticket in the system.
On my amplifier it was once the 6bw4 or Ez80 that won the race, it often depended on knowing the basic tone with the output tubes and what was still missing.
In the end, it was just a matter of a handle and the finalisation was done if you knew your rectifier tubes.
I can't go into the rectifiers explicitly here, but here are a few examples as a key:
Electro Harmonix Ez80 hardly not coloured the sound at all, but it was mostly the most authentic with the driver+output tube pairing, where the true character could be heard.
Telefunken EZ80 has a slightly warm but neutral sound image with good stage depth and resolution.
Mullard Ez80 plays warm and deep on this point.
6BW4 Sylvania, warm, creamy, with good bass response, the Rca was a little less of everything here but also very solid and tendecally more neutral.
As I said, in the end it always came down to the fact that if something was still missing, there was still some room for manoeuvre.
If you don't have a rectifier on the amplifier, it doesn't matter. I don't think it makes too much difference here.
The final polish can be solved and found elsewhere, like with cables.

Now to the impressions:
12AU7 RAY from APOS AUDIO was always the main driver tube that stayed in, in the amp.
The output tube was always replaced and, if necessary, also the rectifiers, the latter being more a matter of personal listening preferences and coordination with the ZMF Atrium.

Brimar KT63 in the output:

A forgotten tube that sounds amazing, the low end in the vocals on the hihats comes across very well without being annoying and is expressive.
Bass was not so focussed, but expansive enough.
Tonally, it is a little warmer and was very well suited to relaxing.
The mid-range was nice and clean here, tender and a good bit long-lasting even in the decay very pleasant to hear.
The instrument separation was clean here, even the illumination in the rear rank was perceptible here, guitar riffs were a good example of this.
It was a pairing that was in the system for a very long time and was a very pleasant ear caress.

EL81 in the output:

The Mullards were very mellow here, sometimes I wished for a little more punch in the bass, but once you get used to it, it's fine.
It was very delicate to the music, rippling and rattling was very well perceptible and in flow, the instruments very well represented and a bit more biting and authentic than with the KT63.
Vocals very organic and slightly emphasised in the foreground. Tonally everything else was just right.
The Siemens was generally more neutral in sound and a little more powerful in the bass range, the rest was similar to Mullard, especially with the instruments and the 12AU7 Ray from APOS AUDIO.
In the end, the Ultron EL81 was my favourite next to the Mullard, which is Mullard/Siemens together.
The absolute best EL81 tube for my ears, the bass was punchy enough, the keystroke of the piano was on point, the violin bowing was delicious, and the guitars were wow.
Attacks, percussion, the whole drive was absolutely right here, even the macro focus was absolutely great.
The vocals were full-bodied and strong but tender at the same time, and the low end got under your skin.
It was one of my personal favourite pairings.

20231204_193028 (1).jpg

6K6 Nec and others in the output:
Also a forgotten tube from the old days, and tonally they are all very close to the music.
The instruments are very close and in tune, sounding very benevolent, and the focus on how the instruments sound can sound very authentic with this tube.
Even the 6V6, which came later from a historical point of view, doesn't manage this. 6V6 was the successor to this tube.
There is definitely more music in it and excellent with the 12AU7 Ray from APOS AUDIO.
12AT7 has a bit more bite on the upper edges, while here 12Au7 is a bit softer in articulation and upper edges.
The Nec is neutral here and a true Japanese tube, the overtones are smoother and not as annoying as with more modern Chinese tubes.
There's always something British for the golden ticket here, and the 12AU7 from APOS AUDIO actually came dangerously close.
The Tungsol 6K6 is pure musicality at its best, the plate of the guitar when it goes down is tenderly perceptible when listening closely.
I felt most comfortable with the Tungsol, they were absolutely breathtaking.
Visseux 6K6 a little less like Tungsol with more definition on the upper levels, and generally a little more relaxed but also good musically.
Kenrad 6K6 sounded a bit like Nec and Visseux, a bit sterile but musical, the 12AU7 from APOS AUDIO breathed some life into it compared to other 12AT7s and brought the right warmth.
A 6K6 tube and with the 12AU7 Ray from APOS AUDIO generally nothing was missing, everything was where it should be with all the tubes and the separates were the icing on the cake with the instruments.
Also in terms of macrodynamics, even over loudspeakers, it's definitely a tube that I really appreciate from a personal point of view with this amplifier.
It's not just fun and can also play in a relaxed way, but the drive it brings to the music makes it come alive - absolute enjoyment and the Ray did a very good job here.

6V6 Mazada in the output and others:
The combination with Mazda was the best here, with a beautiful, lush, warm yet neutral sound that gives a deep insight into the stage.
The details play deep down and push through nicely and cleanly, the macrodynamics are absolutely right here and have almost reached the 6K6 tube level.
The mid-range is slightly in focus and in the foreground here, while the bass and treble are more discreet.
All in all, it's a musical combination of the released kind with a lot of information about the music, as good as a good French kind of combination.
Everything is silky, smooth, fluid and in full flow, and the instruments are also well integrated into the mid-range and play as if from a single mould.
The bass is punchy or softer depending on how it was composed and the upper range remains sweet and stretches out without being annoying.
The vocals are also a nice top end here, and the Mazda ended up being my favourite with the 12AU7 Ray from APOS AUDIO and Cayhin friends will certainly like it.
RFT 6V6: Here absolutely totally neutral almost no warmth and the 12AU7 Ray from APOS AUDIO tries it´s best here to give something of what it has.
It plays almost a good bit analytically and is also somewhat sterile and dry in sound, but tonally the illumination is still there, but you notice that some soul is missing.
As a counterpart here would be a driver tube that would be even warmer and a good player, so that it doesn't sound as described.
Although the bass is powerful and present at this point and the mid-range is its domain, the upper end is almost too much for me.
Westinghouse 6V6:
Very warm tonal here, sometimes almost a bit too thick with the Atrium which is also on the warm side and makes you want to change pads more.It was more Zmf Auteur like in this term.
I really liked the mid-range here because it moves a nice bit forward, the bass range is punchy and lush, the top end is not annoying but sometimes too much in decay.
The instrument separation is also clean and smooth and well staged, not quite as nice as with the Mazda, but again that's personal listening preferences.
Overall very good with the pairing if the headphones are a little more neutral in terms of tendency.
Sylvania 6V6 VT107:
Similar here to the 6V6 Mazda, except that it is a bit more neutral tonally; the Sylvania is also more technical and not as musical, but musical enough in term of sound.
The mid-range is a bit more accurate in the overtones, a bit more V-shaped. The treble range is also well extended and sweeter with a nice recognisable technical flow.
With the instruments, the focus is absolutely present and very well staged in terms of location and recognisability.
The bass is rich and nicely defined from bottom to top.

Mazda and Sylvania were my favourites here in combination with the 12AU7 Ray from APOS AUDIO, both of which unite what music means and how it should be staged.
It was one of the best combos I've heard, both have the class of 6K6, even if 6K6 has a bit more in it.


Sophia Electric EL34:
My idea here was to pair New Stock with New Stock, the plan didn't quite work out here.
The pairing was good overall and I was ready to fall in love, but something really bothered me that it didn't work out.
Tonally warm and lush all there, with a nice splash of neutrality.
I was disturbed by the vocals, which were a good 3-4 metres away from the whole thing, while the instrumentals moved to the front.
And it didn't sound that great overall, a 12AT7 tube made things much better here so you can say it wasn't the Sophia itself.
I suspect that the pairing was too warm overall and simply didn't harmonise together, as there has been nothing wrong with the 12AU7 Ray from APOS AUDIO so far.
Unfortunately, I don't have any other EL34´s that I could test, so I'll add them here if I do.

Gec KT66:
This was by far the world-class pairing for my ear, and I had slight reservations about the Gec KT66 before.
With the 12AU7 Ray from APOS AUDIO i understood why many people like the Gec, which I couldn't quite understand before.
The pairing was indeed the holy grail in sound, it was soft but hard at the same time, in all areas from top to bottom.
The bass was so full and accurate and punchy and always very well balanced.
The mid-range was very creamy and inviting to listen to music, and to want to hear more and more.
The top end is all of a piece and a beautifully clean low end, truly melting, as if you were preparing fresh crème brule and watching the sugar caramelise.
The sugar caramelises in term of sound so good.
The details float beautifully over the head from left to right.
How good the pairing is technically is also breathtaking, left and right separation tonally clean, smooth, in timing and beat.
The instruments not only fit in very well here but also play two levels higher in quality, technically refined as well as sensitive.
The vocals are also in a class of their own where everything is just right, even the positioning, expression and even dialects from the different US states were very clearly recognisable here.
Pauses, breathing, emphasis and volume were also in a class of their own, where everything else was lacking in the original tubes.
Breathtaking is also the class how the recording was recorded, especially older recordings.
Starting off with a hard bass impact that is loud and slowly goes down a few decibels as the vocals start.
My fingers were already on the potentiometer when I realised that this had just happened and released my fingers from the potentiometer.
I really have to think about which 12AT7 I still have that has a similar musical image, I don't think I have anything.
Because the 12AU7 Rayfrom APOS AUDIO is almost the perfect tube for being in 7th heaven.
Another example is the song by Lighthouse Family-Ain't No Sunshine (album version) to give you a feeling.
The bass here is very deep and very layered on all levels, the piano in its fullness as if it were standing in the room and details where gently shimmering and emphasised.
Alongside the violins where the violins are tenderly tuned and in harmony with the vocals of the singer, whose slightly smoky but more gentle voice is pure pleasure and totally emotionally captivating and sensitive.
Live recordings are also very breathtaking and intoxicating to listen to.
People who have a Kt66/88 capable amplifier will love this pairing if they can use 12AU7 Tubes.



General Electric KT 66: Actually the not so favoured KT66 tube and quite wrongly so.
Although it is not a Gec, it is more neutral here and still pairs very well with the 12AU7 Ray from APOS AUDIO.
It did a great job with the Atrium and takes out some of the warmth and thickness here and with the loudspeakers creates a nice powerful, neutral, clean sound with a certain bloom, charm and character.
Not like the sensitive Gec, that's true, but still a tube that served a different focus back then.
I found it took out the warmth and remained technical enough to produce a good sound but on a completely different level that was also very good.
The bass is a bit crisper here than on the Gec, the rest remained mostly neutral and smooth and also more transparent, I tended to like it more on rock stuff.
Here it didn't make much sense to swap the pads on the headphones, it would have been easier to swap the tubes.
If I had wanted a more neutral sound, I would have put in the GE KT66.
By the way,with the ZMF Auteur OG it was suprise sounding at all.Can imagine with the Zmf classic ist the same well sounding.


As a tube hare you have reservations about new stock tubes, but with the 12AU7 Ray from APOS AUDIO you can put them aside.
It beat some 12AT7s in the Nos range where I have them, and the 12AU7 Valvo/Mazda was also inferior here for me (which has also become expensive in the meantime).
Sure there are still some 12AU7 Nos out there that can set the tone here, but at what price?
Of course we're talking about personal taste and money here, but you should give it a chance, it deserves it and will surprise you with what it brings and plays.
You will not be disappointed.
The construction and workmanship is very good, and unfortunately and perhaps it is better not to know the real manufacturer.
At this point Apos Audio must be praised for their mission and work and the vision they have for their 12AU7 RAY.
The work is more than excellent and I personally imagine something like this under New Stock from a sonic point of view.
If it continues at this level then we can slowly say goodbye to Nos if other manufacturers would follow suit.
The company that made them knew exactly what to do, so a big compliment here too, and their wealth of experience seems to be very good.
You shouldn't think about the price here, it's really justified and you get a lot in return, and it's far from the cliché that you get what you pay for.
There are actually new stock tubes on the market that fulfil this.
Of course the caveat between hybrid/tube amps is there and there can be differences, especially with hybrid amps, but in the end you will get a good result.
Of course, tube amplifiers are better because everything comes across better in the overall picture.
Apart from the Sophia Electric EL34, and this is the absolute outlier, I haven't had anything where no pairing didn't harmonise.
They were all very good overall and here and there it could always have been a bit more, that's always the case.
Overall, it was always very satisfying and, above all, there was never too little of the cake.
The golden ticket here is probably KT66/88 tubes paired with an amplifier, which in the end was the best I've experienced.
The tube will also do its dinest very well here in various preamps and offer you something you are probably looking for.
So go ahead and be brave.
All in all, I have to say leave your personal reservations aside, newcomers could be a little braver here and will be rewarded and satisfied.
Tube bunnies and those who already have a collection may have reservations here, which may be true, but I will tell you that there are some who may have their proud nos collection over one or the other.
Nos collection to let go of one or the other tube, thus also have their costs in it again if we are pragmatic.
Otherwise I am looking forward to more tubes from Apos Audio, 6SN7 is already out where I am interested.
A KT66/88 would also be something nice, even an EL34 would be great, and I'm keeping my fingers crossed that everything turns out the way you think it will and that it will satisfy tube lovers.
With the 12AU7 you have already succeeded in creating a piece that is very good and does not have to hide.
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Headphoneus Supremus
A Ray of Hope for modern production tubes?
Pros: In production.
Decent price for matched pair.
Reduced sound coloration, but just enough to be interesting.
Timbre sounds “right.”
More separation and soundstage than average tubes.
Quickly sound great right out of the box, even before the recommended 6-hour burn in.
Extremely resistant to EMI and vibrational ringing.
Secure retail and storage box.
Looks great too!
Cons: Only 12AU7 types right now.


Setting the stage: A finite supply of NOS tubes​

Tube amps can be wonderful and are often beloved in the audiophile community, but they face a supply problem. While many enthusiast threads here on Head-Fi will say the artisanship of constructing valve or vacuum tubes peaked in the 1970’s, they were already facing stiff competition from transistors, and many of the classic companies like Mullard, Amperex, Siemens, Telefunken, RCA, and GE ceased production of audio tubes themselves or even went out of business. The reality is the audiophile consumer market is smaller than the musician and military industries, and once those industries began to move to less expensive and more compact and durable transistors, the customer pool shrank dramatically. Without the financial incentive and many of the “master” factory workers retiring, we entered a few decades of audiophiles going on the hunt to collect “holy grail” samples of surplus, New Old Stock (NOS) tubes. Sadly, top shelf tubes have become rare and their prices continue to shoot up.

However, it seems that there is something of a resurgence of tube popularity, as many tube amplifier options have appeared in the last decade – from very affordable tube hybrids and all the way up to some of the best amps in the world using tubes – and thankfully many of the sophisticated equipment used to make the best tubes from England, Germany, and Holland were purchased from storage and put back into use in Russia, Slovakia, and China to make new tubes!

Why Tubes?​

Generally speaking, why get nostalgic about tubes at all since solid state transistor amplifiers have become mainstream? The most commonly cited and misunderstood reason is the Euphoric “tube sound,” harmonic sounds that give music a more solid body and richer timbre. This doesn’t mean “More Bass,” but this increased complexity can appear more or less depending on what tube you choose. Tubes also Handle clipping more elegantly; instead of sharply hitting 100% level gain and hitting a plateau, that hit is a bit more rounded off to more smoothly hit 100%. Sweeter highs, and sometimes more forward mids are quoted as a better feature… a tube that changes the magnitude of frequency response is a lower grade tube imo, but the other two factors can indeed help highs seem smoother, less threadbare and glaring. Lastly, an overlooked aspect of tubes is that they can be completely capable of intricate detail, and are often chosen for extremely high performance amps, including the world’s best electrostats.


Enter the Apos Ray tubes​

A 12AU7 variant of tube, Apos conveniently lists (and sells) a fairly wide number of amplifiers on their website that can use these, including xDuoo, Bravo, Bottlehead, Cayin, and Woo Audio. The tubes are delivered suspended in a fairly robust block of foam, inside attractive packaging that pleases my graphic design sensibilities.

This is a far cry from my experience buying 6DJ8 old stock tubes from eBay… my two Amperex came directly in little cardboard boxes, protected in shipping by crumpled paper in a larger box, while my Sylvania JAN tubes, Baldwin organ pulled tubes and Voskhod military surplus tubes didn’t even come with a retail box at all and were merely secured by strips of foam and tape before being placed in a brown box with loose packing peanuts to fill the void, mostly. It’s also worth mentioning that my 6DJ8 SET hybrid amp included a tube in its packaging, apparently a quite good one, but I never heard it because it got smashed in shipping. I had a devil of a time cleaning out the glass shards from inside my amp and the grit out of the RCA ports. So, I actually feel the Apos Ray’s protective and easily identifiable packaging is a significant plus for reliable delivery and storage.

I’ll note that the pins are gold plated. Marketing says that this “increases conductivity,” well Gold isn’t a particularly conductive metal… but it prevents rust, and in the long term that WILL improve durability and prevent a loss of conductivity, so the leaf-thin coating is a nice addition.

One piece of marketing that I picked out from the included Apos booklet was that only 4% of the tubes produced and tested on equipment by a sound engineer measured up to their tolerance standards… that figure kind of boggles my mind with how low the yield is on these! The Ray are hand selected, and matched pairs would have to be even more similar to eachother, which is extremely important to providing the sensation of soundstage depth in amps that require matched tubes. If two tubes have similar noise performance but their gain isn’t also matched, it doesn’t just shift the center imaging off to one side, it collapses the illusion of depth into a wall of sound mash. Did Apos succeed in that? That’s a great time to start discussing sound impressions.

Listening impressions​

Though I’ve rolled 7 different 6DJ8 tubes, and attended CanJams and private meets to hear many tube amps (Woo! ALO! Sennheiser HE-1! Blue Hawaii! Though I’ve got to say, the Fostex HP-V7 was one of the most transformative and romantic amps I heard, shame they were discontinued long before I had the savings to buy!), I don’t actually own a 12AU7 amp. Apos Audio was kind enough to lend me an xDuoo TA-22 with stock tubes and the Apos Ray tubes… though these are loaners, and Apos did not offer any financial incentive for a positive review, nor have they read this review before I posted it.

As a basis for comparison, first I warmed up and used the stock xDuoo tubes for two hours, playing some Call of Duty multiplayer and 30 minutes of the 4K Ultra Blu-Ray of the movie Dune: Part One. Side note: the xDuoo cannot directly play audio from the PS5’s USB ports, so I used the optical output from my LG OLED television. I also used a Sennheiser HD 660S2 for evaluation, keep an eye out for a review on that soon. Compared to the solid state amps I typically use, the stock xDuoo tubes sounded syrupy and warm BUT also veiled and the timbre was a little funky, it brought the curious image to mind that all the Atreides were talking through those cardboard toilet paper cores. BAUUUUM-BA-EUUUUUGH?


By contrast, with just 5 minutes warm up and well before the recommended 6 hours of burn-in time with the Apos Ray, the timbre was immediately clearer and sounding much more normal, able to sound both intimate and grandiose, and it was a joy to watch the rest of the movie in this way. Whispered dialogue was as discernible as could be hoped, but more impressively the audio mix didn’t mash up into chaos in loud action scenes with many voices, sound effects, and music all playing at once. After Dune, I went back and played the headphone mix of Call of Duty MWII, which provided the joy of hyper detailed live audio that provided surround sound in reaction to my player character movements, made easy hearing footsteps over the din of directional gunfire at different distances, and kept me engaged and focused well past my bedtime, haha!

To give the stock tubes and Ray tubes a more fair comparison, I let both sets stay warm and active in the TA-22 for two whole nights and days each before coming back to listen to music. To the stock xDuoo tube’s credit, the funky timbre cleared up and provided a closer comparison, but the Ray tubes maintained their clear advantage. I used my Sennheiser HD 660S2 Mixtape playlist on Apple Music for evaluation (it’s a work in progress).
  • “All I Need” from Radiohead’s In Rainbows album was more clearly able to pick out the reverb details on the tail end of each note, better portraying the sense of sound within the boundaries of a space, compared to the more dampened xDuoo tubes.
  • While not sub-bass monsters, the Rays were able to perform the suckout and bass/electronic hits of “Blueshift” by Machinedrum and Holly with a convincing attack, which some people would call good dynamics.
  • “And I Love Her” by Santo & Johnny is an intimate and cozy track in contrast to the prior electronic track, the extra clarity of the Rays did not push the sound too far from the euphoria of the track and I didn’t feel like I was hyper focusing on the Lo-Fi nature of the track or any particular flaws.
  • I did bemusingly note the artificial “analog” and noise added to “Short Change Hero,” but again I was still in the flow of the emotion intended in the track, the detail served in equal measure with the euphoria that tubes are known for. In summary, the xDuoo stick tubes were capable and warm tubes, but the Rays were more delicate, nuanced with a richer insight into recordings, and better at portraying soundstage depth behind the instruments and the listener.
  • “(-) Ions” by Tool is an atmospheric track featuring wobbling sheets of metal and arcing electric sparks that seem to move around the head (very cool on headphones), I picked this track because the buzzing has a lot of texture and it’s a good way to get a sense of detail retrieval and how firm the attack can be with extremely rapidly changing sounds; the Ray tubes in the TA-22 hybrid amp don’t have the coarsest, hardest texture out of anything on the market, but it’s a significant upgrade over the xDuoo and plenty energetic to be spine-tingling.
  • Bonus track, not on the playlist, is “Demons” by Imagine Dragons. It’s a decent song, but one of the most extreme victims of the loudness wars I’ve found, with poor dynamic range and a lot of clipping and distortion (especially in the drums). Tubes can’t magically “fix” lost information and bad mastering, but the Rays do kind of round off the harshness of the drums and it just about makes the most out of the quality of the track, where a high end solid state would brutally highlight these flaws and distract from the enjoyment of the track.
  • “Postcard Blues” by Cowboy Junkies also features a shrill blast of harmonica that was too hot for the mic; it’s always, erm, powerful, but the Rays help smooth and sweeten it to a fairly enjoyable level, even though the HD 660S2 doesn’t cut the highs as much as the old HD 650.

Throughout all of this, even with the xDuoo TA-22 positioned right next to my WiiM Pro streamer and my cellphone, the tubes stayed impressively nonplussed. Despite being surrounded by electromagnetic signals (I even asked friends to text me while I had the music paused), I never heard a single squelching sound of EMI. I knocked on the table, the xDuoo chassis, and even the little v-shaped protective stands, but I never heard the tubes ringing. My Amperex bugle boy tube is so microphonic that it seems to have a subconsciously constant whine all the time, and EMI is what made me previously stop using my old tube amp. Impressive showing here!


The money question: can modern production tubes stand up to the classics of yore?​

In the context of featuring high performance, high value, and high confidence, Apos Ray tubes could be the last stop for many people looking for a great tube experience. The Rays are more comparable to solid state amps with low levels of euphonic and harmonic distortion, and they’re quite detailed, but they they do manage to sweeten the music a bit, striking a nice balance that doesn’t become so full bodied to become muddy while also doesn’t become so analytical that flaws distract from enjoying the music. These MSRP for $179, but there’s an ongoing introductory sale at $149 ongoing as of this review, AFTER cyber Monday. For a matched pair (which is more selective than just picking any two tubes), $149 is a good value compared to matched NOS tubes that are collector’s items, and you get the assurance of 3 months of warranty with the ability to get an exchange if something is wrong.
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This is a very good review. Informative as hell and you give people the strength of “buying power” and good decision making. Nicely done. 👽
Wes S
Wes S
It would be nice/beneficial to see some actual comparisons, to some of the more well know/popular and still widely available NOS 12AU7's. New Production tubes have a lot to live up to. . .:wink:
@Wes S While I’ve heard many tube amps at CanJams and in the offices of companies I used to work for, unfortunately I only own a 6DJ8-based tube amp myself. In the context of an amplifier, different tubes still serve as drivers or rectifiers, and the output quality will show if a tube is capable or crap. While I would generally rank these RAY tubes high, only bettered by holy grail samples of New Old Stock (but there are plenty of old tubes that don’t sound as good), the fact is that the stock xDuoo 12AU7 tubes were the only ones I had on hand, and thus the only ones I felt I could honestly provide a direct comparison and contrast against. My moderate collection of 6DJ8 tubes could not be used on the same amp.


Headphoneus Supremus
Apos Ray 12AU7 vacuum tubes
Pros: - 3 months warranty
- excellent, clear, dynamic, engaging sound
- good quality, reliability, consistency
Cons: - as of now only available in the USA and Canada


Apos Audio kindly sent me a pair of their brand-new Ray 12AU7 vacuum tubes in exchange for my honest opinion. Everything you read here reflects my own experience and thoughts, I am not affiliated in any way.

Apos Audio:

Apos Audio is a California based audio retailer, but they are not your average retailers. They are truly dedicated people, which also shows in creating their own products like the Apos Caspian headphones, audio cables and now tubes. (The Caspian is a $500 headphone based on Kennerton's dynamic drivers.)

Apos Audio is committed to tune, design and produce quality new production vacuum tubes. This is a big deal and shortly I will explain why. The 12AU7 is their first attempt. On this link you can give them ideas what other tubes you would like them to make and what sound you are after. I always find it exciting, when audio enthusiasts want to develop a project with the enthusiast community, as the potential in such cases is enormous. I have a feeling, there are a lot of good things to come from this project!


Why is it a big deal?

If you have ever dipped your toes into the vacuum tube world, I am sure you almost immediately realised the issues with today's vacuum tube market. Vacuum tubes were invented in 1904, mass production started in the 1910's and 1920's. They were used in all sorts of electrical equipment. In 1947 three gentlemen invented the transistor, which effectively replaced vacuum tubes in the 1950's and 1960's. For a period of time, they co-existed, but the cheap and efficient transistor simply killed vacuum tube production.


Gold pins

I could go into a lot more details, but as the end of the 20th century was slowly approaching, more and more audio enthusiasts started to realise that this old technology in many cases sounded better than any transistor-based system. In general, amplifiers with vacuum tubes sound more euphonic, often (but not always) warmer, more lifelike and more engaging. The perceived spaciousness is also often bigger with a more accurate 3D imaging versus the narrower and more 2D sounding solid state amplifiers. To cut a long story short, unused, old stock vacuum tubes became very much sought after items. This, as I am sure you know, led to some insane price increases on the NOS tube market since supply is heavily limited.

Vacuum tubes are not really mass produced anymore, there are only three factories that make tubes these days: in China, in Russia and in Slovakia. These new production tubes are mostly made for guitar amplifiers, but also used in many headphone and power tube amps as stock tubes. The criticism towards new production tubes is often that they do not sound as good, as lifelike, as engaging as NOS (new old stock) tubes. Based on my experience I can confirm this. It is not that new production tubes are poor, simply the old production little glass sculptures tend to sound better.


Another big problem on today's tube market is reliability and fake products. As everywhere else in life, swindlers can be found amongst eBay and other tube sellers too. NOS tubes must be sourced from reliable tube sellers, otherwise you might not get what you pay for. Even if you get what you pay for, these old tubes can fail and even the most reputable sellers usually do not offer more than two weeks return/warranty on them. Buying NOS tubes unfortunately is not only expensive but also a bit of a gamble.

Based on all we have read so far; the question might arise: why cannot we produce new tubes that sound as good as the old ones? This is another complex topic, enough for an essay. The main point is, producing good tubes used to be quite a special craft. The best tube making masters were highly respected. With the spread of the transistors, this craft got slowly forgotten. Nobody wanted to learn the subtle art of producing quality tubes anymore. Most of this knowledge died with those masters, and the little paperwork and documents we had got burnt or lost in World War Two and other disasters.

By now you might see why it is a big deal that Apos Audio took on this mission of creating high quality new production vacuum tubes. Let's see, how their first attempt looks and sounds like.


My tube background:

I have been in the hobby for 12+ years. For a long time, I kept delaying my involvement with tubes as I always thought it was a too finicky and too expensive circle of audio hell (heaven?). Then about a year ago I bought my first transformer coupled tube amplifier, the Cayin HA-3A. It did not take long to get into tube rolling, I tried a bunch of 6V6, 22DE4 and 12AU7 tubes.
There are far more experienced members here than me when it comes to tube rolling, but I managed to gain a good insight into what rolling NOS tubes mean. I bought noisy, unmatched or simply unimpressive NOS tubes and also bought some absolute beauties. 80% heaven, 20% hell is my balance when it comes to my NOS tube purchases. There are so many different versions even of the same type of tubes and they behave differently in each system, so regardless how much you read about a certain tube, eventually it will be a blind buy and a gamble to some extent.

All that said, I simply love tube sound. Once you find the right selection of tubes for your amp and system, the sound is incomparable to most solid-state amplifiers. Gone is the digital and plasticky timbre, everything comes alive and sounds soulful, organic; not to mention the enhanced spaciousness. Good tube sound evokes emotions.



The 12AU7 is a popular type of vacuum tubes, many amplifiers use them. This was an excellent choice from Apos Audio to start their adventure with.
In a nutshell, these Ray tubes sound very good! They offer the warmth one would expect from tubes, but they do not overdo it and remain very clear and spacious. These are clear, detailed sounding tubes with excellent dynamics. Spaciousness is superb, the higher frequencies are airy and open while the low frequencies are solid and detailed with good separation. The presentation is lively and fun, I find it very entertaining. Instrument separation is excellent with the lifelike timbre qualities you would expect from a pair of 12AU7s for $180.

Bass has good extension, good body, clarity and impact. It is strong enough, but never overwhelming. Mids and treble are both very clean and clear but retain the subtle warmth which most people associate with the 'magic of tubes'.

Layering and depth perception are both excellent, the punchy and dynamic sound is very enjoyable. I do not feel the boring, flat and slightly colourless impression of other new production tubes here, Apos's new 12AU7s can truly compete with some proper NOS tubes. Let's see what their position is in this tough competition.




These are new production tubes made in Slovakia, a matched pair retails around $40-$50 and they were also the stock tubes in my Cayin HA-3A. These are good quality and reliable tubes, but do not sound the most interesting. In comparison to all other 12AU7s I will mention here, these sound a little lifeless, a little flat with lesser depth, but the most painful part is a relatively rolled off and not very energetic bass performance. To my experience a rolled off and weaker bass is the biggest challenge to most 12AU7 tubes, regardless of whether they are new or old production.

RCA Black Plates:

These were one of the first NOS matched pair tubes I bought for around $80. I enjoyed the more natural, more coherent sound compared to the JJs. These also sounded a bit more spacious, but I had similar issues with the bass performance. The lowest frequencies did not have the body and impact I am after.

Mullard M8136 CV4003 (old and new logo):

The old logo versions of these are my favourite 12AU7s to date. The new logo Mullards are nice too with a lot of warmth and a very engaging, euphonic sound, but the old versions offer more clarity and definition while keeping the same excellent tonality and timbre. The new logo versions (~after 1970) are around $220, the old logo Mullards are around $300 (~pre 1970).
Both versions of the Mullards are more expensive than the Apos Rays, and to my ears this is reflected in their sound too, especially when it comes to the old logo M8136. Compared to the Apos Rays these legends sound a little smoother, a little more coherent and refined. The Apos tubes hold up very well though, for $180 they offer pretty much 80% of what these Mullards are capable of. On these military spec (better reliability) NOS tubes music still sounds a little more natural to me, sub-bass is still a little more present, and it feels as if there was more control and grip in general.



Where do I put the Apos Ray 12AU7s then on today's tube market map? I think they are excellent sounding 12AU7s and by far the best sounding new production tubes I have ever heard. They are able to compete with some 'new old stock' tubes, even sounding better than many of them. The Ray 12AU7s offer a very exciting, clear yet colourful and engaging sonic experience. They only start to fall a little short when we compare them directly to the most regarded NOS 12AU7s which are also significantly more expensive. If you also take reliability (dead silent, noise free) and the three months warranty into account, we might just be witnessing the birth of a winner! Apos Audio's first tubes sound great, they offer very good value, and their future plans are inspiring! What not to love?
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Great write up. How many hours of use did you have on these before reviewing them?
@theredmantra Thank you! Apos Audio suggests a 6 hour burn in time and a 10 min warm up time. I did not start to evaluate the tubes until I reached 24 hours burn in time and usually leave 30 mins for the warmup as well.
S Crowther
S Crowther
Unfortunately Apos do not ship outside US/Canada.