Replacing 5U4G with 274B's - Which 274B's are best?

[GJcoffeeman]

---

I am experimenting with replacing some 5U4G' rectifier's for modern 274B's in my system. The traditional WE 274B's had a lower output current (150ma) and did not have the tolerance to substitute directly in the 5U4G slot. But several models have evolved with a higher output (220-225ma) and can be used in place of the 5U4G--they even tout it. Four such tubes are:
Takatsuki, Sophia Electric Aqua II, Acme PSVANE. and Elrog.
It would be fun to try all four brands in a head's up comparison, but it begins to be an expensive proposition. In my case, I would need three of each brand to do a full comparison in my chain: one in each of two 300B power amp monoblocks and one in an all-tube DAC.
Has anyone had good results with any of these as 5U4G replacements / upgrades? And has anyone compared the sound characteristics of the latest iterations of any these four tubes?

 

[Anyoldears]

I have had 2 Sophia Electric Aqua IIs. They sound great. Both blew up, the first time requiring the DAC to go back to the factory...

 

[GJcoffeeman]

Did they blow up pretty quickly, i.e. there was an immediate reaction to the tubes when connected with your Lampi? ...or did it take a while then they died? This is an important point for me on my end. Thanks.

 

[Anyoldears]

They lasted about 6 months each

 

[VinylSavor]

---

But several models have evolved with a higher output (220-225ma) and can be used in place of the 5U4G--they even tout it. Four such tubes are:
Takatsuki, Sophia Electric Aqua II, Acme PSVANE. and Elrog.

Where did you get that from? We do NOT recommend to use the 274B as a replacement for 5U4G. There are several issues with that: The 274B has lower current capability than the 5U4G and lower peak currents which results in smaller allowed input capacitance after the rectifier. Another important point: the 5U4 has a 3A filament vs a 2A filament in the 274B. Each power transformer has some degree of load regulation. if it is designed to deliver 3A on the rectifier filament winding and you only load it with 2A it will result in higher filament voltage.This voltage variance will be on top of any mains voltage variation and can easily push the filament voltage outside allowed limit. In the other case if the filament winding is designed for 2A and you load it with 3A, it will not only potentially overload the power transformer but result in lower filament voltage which again can shorten tube life.

I have seen modern 274B which were just relabelled 5U4 and there are some modern 274B with a higher filament current than traditional 274B. In such cases a substitution might work.

But in general a circuit should be designed to work optimally with a certain rectifier type and that should be used.

Best regards

Thomas

 

[GJcoffeeman]

Thomas, thanks for the response. The reason I pushed this topic was to clarify. I believe at least two of the brands listed do specifically refer to interchangeability between the two tubes. My mistake to lump them together. I did see a higher output current in all of these, more than the older WE tubes original 274B's. But the response you gave was the most straightforward I've been able to find. Better to stay safe and duly advised. Thank you.

 

[Cellcbern]

I can only speak to rectifier performance in My Modwright PS 9.0 power supply (for the modified Marantz SA8005 SACD player with analogue 5687 tube output stage), because that is the only component I own that takes a rectifier tube. I have tried a number of 5U4 brands/models, and many different rectifiers that are substitutes for the 5U4G, including 5AR4 (Phillips metal base), GZ37, 5R4GY, 5R4GYS, GZ32, 5Y3GT, etc. The Modwright PS 9.0 will not accept a standard 274B, but accepts Sophia's Aqua 274B which is designed for a first power supply capacitor up to 47uf. Two rectifier tubes stand out for me as being head and shoulders above the rest in this device - the 1950's U52 5U4G CV575 (I've seen them labeled Brimar, GEC, Marconi, and MWT), and the Sophia Aqua 274B (currently using the 2nd generation version). The Sophia is a little more resolving and modern sounding, but both have uncanny resolution and spatial characteristics while being unfailingly musical and natural sounding. All of the others I've tried sound a touch veiled and compressed by comparison. Though not quite on the level of these two the 1950's Mullard GZ32 is a very good rectifier available for less than $100. Good used U52 5U4g's by contrast are approaching $1k per tube.

 

[GJcoffeeman]

Cellcbern Thanks for your note. I had seen that others were using the Sophia Electric 274B Aqua II and not reporting issues. But the note above by Anyoldears about his blowout with those same exact tubes--twice--in a Lampizator DAC adds to the notes of precaution from Thomas Mayer of Elrog and others. It appears that your Modwright works just fine with them. I am thinking of either going back to the search for (pricey) highly touted NOS 5U4G's or just stick with the Sophia Electric 5U4G's that I have, which I think are very good, esp. as a non-NOS alternative. I was encouraged to consider the 274B Aqua II as an "upgrade" from the 5U4G version. I would hate to have a possibly questionable, not-perfect-fit valve cause damage to the unit over time. As Anyoldears reported, it may not happen for a while then eventually cause a meltdown...

 

[Rob181]

Cellcbern Thanks for your note. I had seen that others were using the Sophia Electric 274B Aqua II and not reporting issues. But the note above by Anyoldears about his blowout with those same exact tubes--twice--in a Lampizator DAC adds to the notes of precaution from Thomas Mayer of Elrog and others. It appears that your Modwright works just fine with them. I am thinking of either going back to the search for (pricey) highly touted NOS 5U4G's or just stick with the Sophia Electric 5U4G's that I have, which I think are very good, esp. as a non-NOS alternative. I was encouraged to consider the 274B Aqua II as an "upgrade" from the 5U4G version. I would hate to have a possibly questionable, not-perfect-fit valve cause damage to the unit over time. As Anyoldears reported, it may not happen for a while then eventually cause a meltdown...

Have you looked at this thread - it may just have a genuine alternative for you...

StradiTube.. review incoming (any requests?)

Hi Everyone, I was having a deep late night dive into rare Telefunkens a few months back and came across Stradi Tube from Korea. I was super curious about what they offered, given they make modern replicas of a lot of classic German DHT tubes which no-one else does. They also have some rather...

www.whatsbestforum.com

 

[GJcoffeeman]

Thanks Rob! I just spent time reading about them and have just ordered one of the 5U4G's to see how it goes. I sure we have found a new quality source!

 

[nortberg]

Thanks Rob! I just spent time reading about them and have just ordered one of the 5U4G's to see how it goes. I sure we have found a new quality source!

Have you received the Stradi 5U4G yet?
Very interested in your thoughts about this one.

 

[GJcoffeeman]

Yes, it arrived this past week but I haven't had time to install it and burn it in. I'm also waiting for a pair of NOS 5U4G GEC U5 tubes (brown base). I'll shoot back some commentary when I've had time to try them both in my system.