I originally thought this was a SQ (special quality) model just like the one above, but I'm not so sure anymore. There is no SQ marking like on the Miniwatt. Both have a o-ring getter but the one on the Miniwatt is much smaller.
E188CC Valvo Code: VR9 ⊿9F1
Got this tube with the Valvo tube below for about €40. My favorite tube so far. It does not have massive bass like the Miniwatt but it is far more balanced than any other tube. You can hear practically everything over the whole frequency band. The soundstage is amazing. Much more open and just smoother than the other tubes I have. This is my daily driver at the moment and it will be until it dies or I find a better tube for a reasonable price. I don't want to pay €150 for a CCa or Siemens E188CC. It is just too much.
I also noticed that this tube does not have any hum or microphonics at very high volumes. Absolutely NOTHING. I was fascinated. Most of my other tubes hum at high volumes and they behave microphonic. You can test it yourself by putting the volume at max and tapping against the tube. If you hear that tap in your headphones your tube is microphonic.
E88CC Valvo Code: 7LG ⊿0C3
This is the tube I got with the Valvo E188CC. It's an okay tube. I guess it has seen its best days because it sounds quite different than the other Valvo E88CC below. It's still an okay tube, but nothing more.
E88CC Valvo Code: 7LG ⊿0I4
Got this tube also for about €5 and holy mother of bass! This tube is really bass heavy. But it's treble is also through the roof. It almost hurts my ears. I guess I have to lower them in the EQ. This is just too much. Unfortunately the mids are suffering because of this.
E88CC Siemens Code: A64G
A tube marked with BWB (Bundesamt für Wehrtechnik und Beschaffung). It was most likely used in the german military (Bundeswehr) and found their way to me for a reasonable price. Although they were quite heavily used they still sound very nice. My favorites next to the Valvo E188CC. Compared to the Philips E88CC they have a better soundstage, a little bit less bass but more treble. In my opinion more balanced.
This is the one with the single stage plate getter.
ECC85 Siemens Code: ?28 ⊿9G4
I don't really know why I thought it was a good idea to get these ECC85 tubes. They have a much higher heater current than the E88CCs and I'm not sure if the T1 can handle that over a longer period. This is the only ECC85 tube from the 4 I got that actually works in the T1. It sound okay, but nothing special...
This one has a disc getter.
ECC85 Siemens Code(s): 1U8 ‡1B, 1U7 ‡5K, 1U3 ‡7E
Stay away from these. Completely distorted sound. It also hums like crazy. Even at normal volume. Nothing to see or hear here...
They have o-ring getters.
E288CC Valvo Code: N60G
My first E288CC. It isn't a direct exchange for the E88CC family, well, at least normally. But it fits just fine in the Aune. It does have a higher heater current so the tube gets quite hotter than E88CC ones. These tubes go for at least over €100 on eBay. Really good NOS tubes are even more expensive. I waited long enough and got a really nice deal. I bought one tube for €35. NOS! This tube looks perfectly. Also remember this tube is about 2cm higher than E88CC tubes. The guards will still fit but you have to experiment with the placement.
The sound is really nice. Compared to the E188CC the bass is not as strong but the difference is only really marginal. What I really like about the tube is the fantastic soundstage and better mids. It also has a much more warmer sound than the tubes from the E88CC family. I really like it. But I would only recommend the tube if you can get it for a reasonable price.
EDIT: After several hours of listening this tube really starts to open up. The sound is so open it makes my head fly. Very nice!
No hum or microphonics on this tube! Excellent!
This one has an O-ring getter.
E288CC Valvo Code: N65A
This one is a little bit different than the E288CC I got before. It has a single stage plate getter. But it is my favorite tube so far. It's like the other E288CC but it is warmer. The bass is a little bit more intense and so is the treble. Soundstage is the same which is great. Still the same great open soundscape. As far as I know most if not all the E288CC tubes were made by Siemens so it shouldn't really make a huge difference which brand you buy if the getter type is the same. Unfortunately they are very hard to find or extremely pricey. I was lucky two times and I don't think I will be again.
All reviews were made with a Beyerdynamic DT 770 Pro 80 Ohms!
These are all my tubes I have at the moment. I will try to add more tubes if I get more and also update the reviews if the sound somehow changed.
Changing caps!
Here are some pictures of the process.

I changed the headphone coupling caps first (right ones). ELNA Silmic II 47µF 50V. You have to bend them like that otherwise there is no other way to fit them in there. The old ones are ridiculously tiny.

Here are the rail voltage caps. ELNA Silmic II 470µF 25V. And they are huuuge. Good luck fitting them insde the case. I had to bend them like that .
The secondary supply caps were really tricky. I wanted to close the case so I had to improvise. I took some wire and twisted them like in the picture. This is important for reducing the inductance of the wire. I positioned the caps on the right side of the case where there is a little bit more room. Then I fixed everything with tape. Don't forget to fix the caps inside the case too. I used tape for that too. But you can't see it in this picture.
The main supply caps are still the old ones. I'll change them tomorrow if I got my new ones.
Puhh..and it still does turn on! I need to let the caps break in until I make my decision on the sound quality.
In the front you can see the old caps on the right side. Still got some of the ELNA Silmic II left as you can see. Always good to have some spare parts.
About the sound difference: I definitely recommend changing the caps. They make a huge difference. The volume is now through the roof. I did notice and increase in the mids and lows. They also improved the soundstage. I never thought changing caps would make that much of a difference.
I also replaced the really bad Lelon main power caps with Panasonic FR 3300µF 25V caps. They also were bigger than the old ones. I didn't think that I could fit them all inside the case but I managed to do it. Everything is in place and the T1 still works.
Soundwise they don't make any change at all. But Lelon is famous for making very bad quality caps. No harm in changing them.
Many thanks to CoiL for suggesting the caps and more help!