Sovtek 12AX7LPS tube is the best value for HiFi Audio.
Sovtek 12AX7LPS has a long ribbed plate derived from Siemens design. 12AX7LPS has great low-mids that provides warmth without the mud or spitty highs.
If you are looking for the right warm tube sound at a great price point, Sovtek 12AX7LPS is the best value there is.
We sometimes get questions regarding the filament of 12AX7LPS. The light from the filaments in 12AX7LPS is hard to see, even when it is fully lit. You can be assured this is perfectly normal and is by design.
The reason the filament seems dark on 12AX7LPS is that the filament ends are purposely hidden to minimize noise from the filament. This takes more precision in assembly and only a handful of 12AX7 tubes are put together this way.