12AX7A and 7025 tubes. The same?

I have three pairs of 12AX7A tubes two pairs of 12AX7A Hit Ray, a Japanese joint venture in the 60's between Hitachi and Raytheon (these are damn cheap and beautifully sounding tubes despite all the hype to Mullards or Telefunkens) and one pair of late 60's 12AX7A.
I also have a pair of Hitachi 7025 tubes which also sound outstanding.
If my understanding doesn't fail me, the 12AX7A tube is a lower noise and less hum of the original 12AX7 tube. Also, the 7025 tube is a lower noise and reduced hum version of the original 12AX7 tube. Both can be used where a 12AX7 tube should be used so they are fully compatible with the original design.
Both my 12AX7A and 7025 tubes sound dead quite clean, they have very low noise and hum is vitually inaudible, unlike some other 12AX7 tubes I have.
Are the 12AX7A and 7025 tubes actually the same tube, or are they different designs looking for the same goal?
I'm just curious about it.
Thanks in advance for your replies.

 

A 7025 is a 12AX7 except for a low noise spiral heater (RCA refered to it as a “single helical hairpin heater”), which should make it quieter than a standard 12AX7.

A 12AX7A can be used with heater circuits wired in parallel and series, whereas the 12AX7 can only be used in parallel circuits.

 

Thank you for your reply. Both my Raytheon 12AX7A and Hitachi 7025 sound very very quiet with very low noise and hard to hear hum on my Phono preamp turning the volume all the way up on the amp.

 

@BIGGER Dave has it right. Essentially, 7025s are like super-12AX7s. They operate the same way but the 7025s test higher in some ways. They're interchangeable in amps so enjoy tube rolling.

 

Thank you! A pitty I could only get those Hitachi 7025 dirty cheap (around 45 € including shipping to Spain) and they were NOS tubes. I've seen Shuguang 7025 tubes for little money but I doubt they are actual 7025 or they sound good. The Hitachi 7025 I have sound outstanding, not only super clean but also very smooth with silky mids and highs. What are other nice 7025 brands I can get NOS and cheap on Ebay?

 

@Kiko1974 and the rest of members here, this was the exact thread I was looking for and made me sign up!
Kiko, could you recommend where you got those Hitachi 7025 to fellow Iberian Peninsula member?
I’d like to start some experimentation with a “tube drawer” myself.

 

Hello my fellow Spanish. I have bad news from you,if you don't want to spend a leg and an arm on NOS tubes living in Spain you/we just have eBay, but don't look for them on Spanish eBay because you won't likely find them. Start with UK and US eBays.
Those Hitachi 7025? I got them a year ago and I haven't seen any more of them since then, if I had I'd have got more. I also have Hit Ray (a joint venture of Hitachi and Raytheon in Japan in the 60's, tubes were made in Japan and bear the Hitachi logo) 12AX7A and 12AU7 tubes which sound great to me, as good and as quiet as the Hitachi 7025. But I also have bad news regarding the Hit Ray 12AX7A and 12AU7, I got four 12AX7A and two 12AU7 from the same seller, the 6 of them new and in their original boxes, and that was it, I also got them around a year ago and I've never seen them again, if I had I also had bought more.
If you want good Japanese tubes that sound detailed yet warm look for NOS Matsushita 12AX7, they use a Mullard design and they were made on Mullard tooling, and the good news is that they show up in NOS condition on eBay from time to time.
If you want good 12AX7 tubes and don't want to wait for NOS tubes to show up on eBay, I received a week ago a pair of TJ Full Music 12AX7 tubes. Yes, they're a Chinese brand and of course are made in China but they are on a different league as Psvane (which are not bad but not as good as NOS tubes) or any Shuguang or New Sensor made tube. They are very detailed,very revealing,their sound is smooth and warm and these are the ones that are staying on my Phono preamp, I love them, I didn't expect such a quality from a new production tube. Of course I'm not selling all the NOS tubes I own.
If you're interested on the TJ Full Music 12AX7 you can find them here: New Matched Pair TJ Fullmusic 12AX7 ECC83 Vacuum Tubes for Vintage Guitar Ampx1 | eBay

 

Thank You @Kiko1974, I'm on a mission now! will let you know what I discover, all the best