It's been brought to my attention that 12AU7s are not always interchangeable with 12AT7 or 12AX7. I've happened to have a couple of amps that could accept both 12AU7 and 12AT7 so I was slightly misled by my experiences. Apologies for the error!

While pin out is identical between 12AU7, 12AT7 and 12AX7, you should NEVER roll tubes between these various types in most applications. The 12AU7 is a very low gain triode, the 12AX7 is 5X times higher gain, requiring very different biasing circuit. For some older guitar amps and preamps that may have a variable resistor for manual biasing, you can interchange as long as you have dmm and the knowledge/skill to properly setup the circuit for that tube. The 12AT7 is a medium gain triode, 3 x the gain of the 12AU7. I’ve never heard these new Apos , hopefully they are as good as you claim and are widely available. I’d still prefer the NOS Amperex D-getter from Holland, though they are VERY difficult to find and 70 years since production shut down. The Bugle Boy branded Amperex also are quite good. I personally avoid Telefunken in all 3 variants of ECC81(AT7), ECC82(AU7), ECC83(AX7), though their 6922 are quite decent. 70’s Mullard 12AU7 would be interesting comp to this nee Apos Ray as NOS stock is still reasonably plentiful and price for matched pair is very similar.

Plus one for your, much more experienced, impressions. I’m a tube noobie. Heard my first tube amp at the Schittr this past Xmas and realized that all those tube-heads paying big bucks for more distortion than Solid State, were (surprise!) not living in placebo heaven. Started budgeting. Then Josh V came along effusively praising the Xduoo TA-22 balanced tube DAC/amp and I jumped on it. Enjoyed it more with dynamic drivers, including my personal flagship, the Focal Clear MG. But didn’t think I had matched my “Schitty“ experience. Planned to upgrade to a better tube amp in future. Then Apos announced the Ray. I have felt Apos to be a brand truly trying to be an audiophile resource, so knowing they were pricey I bought the Ray pair from them, trusting in their expertise which I lack. One of my better “Here goes nothin’” decisions. I no longer have upgrade plans, just plans to move the amp plus Rays into a main system preamp configuration so I can hear what they do with my speakers!

12au7 tubes are not fully interchangeable with 12ax7 and 12at7. The au has much lower gain and higher current output.

That is great news about the Apos beeing that good. Stocks for NOS are thinning out and prices increasing, so great that we are getting new production tubes at good qualities now.

I find it amazing that there are still warehouses full of tubes made decades ago.

thanks for the analysis! hopefully they will flesh out their line and maintain the quality across it as well

Thanks for tube coverage.. I have multiple tube amps and agree that tube rolling is a very important part of the amp sound but also a fun part. I have a great collection of NOS tubes so will have to check these out when they come out with 12AX7.

Thanks for a great review I’ve made the move back to tubes and bought a pair of 30 year old monoblocks. Four JJ ECC802S in each block and Four NOS 6C4C power tubes in each. The new amps have killed some harshness I was getting from Lowther based speakers so it’s particularly important for me not to change tubes and put that back in the system. Apps Ray sound like they’ll do what I need and put a little sparkle back. Prices aren’t terrible compared to a lot of other premium price tubes. JJ Black sable reviews suggest they can put some harshness into the top end. I’m in NZ but Amazon will ship them.

I have a similar setup with the same speakers (Harbeth P3ESR-XD) but with a Muzishare X7 amp (KT88). I tried the Electroharminox 12AU7 Gold (balanced pair). I didn't care for them at all. Like you mentioned they are brighter sounding. But the deep, 3D soundstage I had previously enjoyed was almost completely gone with the Electroharmonix tubes. Tempted to try the Apos Ray tubes. I see they have a 45 day return policy which is nice.

Hopefully these new production tubes are a success and Apos starts making 6V variants as well like the ECC88 since I have mostly tube amps that use those.

no 6sn7's yet 😭 i'll keep an eye on them, thanks duderooney! ✌😎👍

This family of tubes isn’t universally interchangeable. I wanted to lower the gain of a Traynor guitar amp I replaced a 12AX7 in one position with an AU7 and I instantly smoked a plate resistor. Easy fix with the replaced resistor. Just be cautious and be smart. Check the work.

I use a 6922 in my Woo OTL, recently changed to using a socket adapter that converts them to a 6SN7. The adapters are available for the 12AU7 also. There is no way I can change back because the 6SN7 gives so much more stage and room size to everything. It is ironic the timing of your reviews, I have literially just pluged in my new 6SN7c (Coke shape) and they are better than my Tungsol.

Always appreciate your input Lachlan. Any personal experience with anything in the Feliks Audio line? What can we do to get Zach to send you a demo decware/ZMF OTL??

Which tubes should i roll to affect the sound of my integrated amp? I have a total of 10 tubes. Output tubes, rectifier tubes, preamp tubes, and a couple others. Any help would be appreciated. Cheers.

If the AposRay is as good as the Amperex 7316 or Raytheon 7028, then shout hallelujah. Those valves were epiphanies. I had read the great HP mentioning sound stages that were "lit up all over", and these two were responsible for my hearing it. But I don't know if they are even available. I bought mine back in the eighties, and i had a hell of a time finding good ones then. Does anybody here listen to IEMs with tubes? Interesting you mention Ken rad 6sn7. The ten or so ive heard, mostly Vt231, sounded bassy. What would be a good 12au7 tube amp for IEM?

Still waiting for Ananda Nano's review and comparison with similar headphones. When are you tentatively planning to post the video on that?

Great video again! Only quality content! I have use nos tube but for my 1978 yaesu radio communications and power amp! In the music/audio department I only have a duo 601 pair with a Sennheiser 58x! Always wondered how it will sound by changing the tube, but spending more than double of what my duo 601 cost in a tube have stopped me to do sow! Do I make the purchase or just get another tube amp! And do I need another amp for just my 58x, if I get another amp do I need to get a better headphone? That the question I always get in my way when in searching, and just stop and don't get nothing! Lol

Cool new tube! Not sure they’ll outshine my Telefunken G73-R (about a $400-$500 single tube when you can find it NOS), but I’m pretty curious to hear these. You never know!

Having a xDuoo TA20+ on its way to me soon and RayTubes not available here in Germany, the ElectroHarmonix with their deeper and slightly tubier sound might pair well with the TA20+ being a hybrid :) Psvane Art series are also on my watch 👀

Great KZfaq channel and please get Ray co to make KT170 tubes and 300b tubes.

Lachlan, have you been to or bought from Tube Audio @ Latrobe st? i'm looking at their Gold Lion

Never touched my tubes with bare fingers - is that ok now with these?

Silicon or death.

You really shouldn't put stuff out if you don't understand the subject. 12au7 are not simply interchangeable with 12ax7 or 12at7. They may light up and make noise but you'll be tampering with linearity and moving the amp away from spec. People listen to you. You owe to your viewers to be informed.

Psvane is pronounced puh-van

there is something odd with the sound quality of your voice, like the extra encoding made it worse