Sophia Electric™ 274B tube is a premium rectifier tube for 5U4/5R4/5AR4* direct replacement.  It has much longer(3X longer) plate structure, thus it has a deeper, wider sound stage and even smoother sound than Mullard 5AR4.

Historically, WE 274B was designed for the WE 300B amplifier. The price for an Used condition WE 274B is in the range of  $2,000 - $4,000 per tube with no warranty.  Based on end-users reports,  Sophia Electric™ 274B tube outperforms the NOS WE 274B by big margin, which translates into better bass, dynamics, and deeper sound stage for the right application.

The sonic difference compared to more common 5U4, 5AR4*, 5R4 is far bigger than any cable upgrades combined in a high-end system.

Sophia Electric 274B is an 8-pin octal-based tube and Sophia Electric 274A is a 4-pin based tube. Our friend Art Audio is using Sophia Electric™ 274B in the Art Audio PX-25 amplifier and several pre-amp makers are using this tube for the high end tube pre amp. Increasingly, there are more users used this tube in the headphone amps with great feedbacks.

Note(*): 274B is a direct heating tube. The indirect heating 5AR4 may turn on slower; however, people who buy 274B are for its much superior sonic performance. To fully utilize its benefits, it may require the first stage capacitor (capacitor input) to be less than 10MFD; otherwise, it would shorten the 274B life span (very much like smoking is bad for your health). It would not be a problem with common choke input. Please consult your amplifier maker or refer to a tube manual. This 274B is an update of the NOS WE 274B, so both share the same characteristics.

The maximum current capability for Sophia Electric 274B mesh plate tube is 90ma, suitable for tube pre-amp and mono-block 45 single ended and 2A3 mono-block single ended amps and headphone amps.

I would recommend Sophia Electric blue glass Aqua 274B tube for 300B amplifiers. The maximum current capability for the original Aqua 274B tube is 160ma and Aqua II 274B would have above 200ma current capability.