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

[GJcoffeeman]

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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]

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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.

 

[ketcham]

The Stradi 5u4g has all the qualities of the GEC U52 but more crisp/resolving. Highly recommended.

Stradi 274B will be released q4 2025.

(KA has No fianancial affiliation)

 

[GJcoffeeman]

I pretty much agree with you, Kevin. I have both GEC's as well as the Stradi. I have tried quite a few 5U4G's, both old and new stock--most of them fall way below these two. My next recommendation would be the 5U4G and 274b from Sofia Electric. They are both excellent and actually work interchangeably in a 5U4G slot. BTW, the SE 274B has indeed been designed to work in most 5U4G slots, unlike the discussion and questions about it earlier in this thread. I dialogued a good bit with Sue from Sophia Electric after some of the previous discussion, plus spent a good bit more time with these tubes. A typical 5U4G has a 3A filament. Traditionally, the 274B's filament is a 2A. However, the SE 274B has a 2.8A filament, not an insignificant difference. And as Cellcburn mentioned earlier, the SE 274B was designed for a first power supply capacitor up to 47uf, so was designed to handle a broad spectrum of the 5U4G demands. It produces a very different, rich sound from many 5U4G's, including their own version at Sophia Electric. Both their 274B and 5U4G are very good and which sound you prefer would depend on where you put them in a chain and the type of speakers/room, etc. They all can "tone" the sound in the direction that might best compliment the whole.

Currently, I'm running a pair of matched GEC U52's in a pair of 300B monoblocks alongside a pair of 300B Tsakatsuki's. I have a/b sampled both the Tsakatsuki's and the Western Electrics. The former were much better for my setup and the GEC's compliment them very well. I have a Stradi in the DAC. The Stradi comes closest to the GEC sound, a little closer than the SE's. It is quite neutral, never harsh, clean at top and bottom, good detail and not overly colored. But the SE's might compliment better in some systems. Sometimes I will change the Stradi for one of the Sophia Electrics. The sound is different but still very musical and will bring out something different. I haven't had the opportunity to try a pair of the Stradi 300B's, but am curious about how they would figure in this! Stradi is definitely going in a good direction and I imagine will become the go-to valve for many.

 

[Cellcbern]

The Stradi 5u4g has all the qualities of the GEC U52 but more crisp/resolving. Highly recommended.

Stradi 274B will be released q4 2025.

(KA has No fianancial affiliation)

Wouldn't want any more resolution/"crispness" than I get from the U52/5U4G and Sophia Aqua 274B in my Modwright PS 9.0

 

[GJcoffeeman]

I thought I would add one more note to this thread. Since my post a few days back, I have spent the past couple of days swapping out the Stradi 5U4G and the Sophia Aqua 274B in my DAC without adding any more valves to mix or changing anything else in the setup. I had been using the Stradi for some weeks and enjoying it. When I put the Sophia back in, I was impressed all over again--what a sweet valve. I will step out and say that, to me, the Sophia Aqua is the closest I have heard to the GEC U52. The Stradi is clean and pretty resolving, but the Sophia is... hate to use a trite phrase but... simply more musical and gives up very little of the Stradi's detail. Very little. Virtually none. I'm leaving the Sophia in place. It won it's slot back and I did not favor it in any way. I'll end with this. If you are looking specifically for the GEC U52 sound but have trouble paying for or much less even finding a NOS GEC U52, your next best valve in the current lineup would be the Sophia Aqua 274B. If you have a system that needs more definition and less warmth (due to speakers, amp/preamp, etc.), then you might want to go with a solid choice like the Stradi or the Sophia Electric's version of the traditional 5U4G. In my case, the choice was conclusive.

 

[Maxamillion]

The Emission Labs 274B works great for me in my DIY 01A preamp/DAC. Not cheap, but definitely a first class tube.

 

[warnie7]

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...

What dac are you using Lampizator web page it says these rectifier tubes are compatible one rectifier DHD : 5U4G or 274B or 5C3S or 5Y3 or GZ37 or 5R4WGB with Baltic4

 

[DasguteOhr]

depends on how big the first filter capacitor is, if it is too big you won't be able to enjoy the 274 for long. If you have a choke input there are no problems. Second problem if indirectly heated tubes are used in the subsequent circuit. They need ~15 seconds to warm up, then you have a high voltage peak on the first filter cap maybe~ 150 volts higher than the normal output voltage. Sometimes this overloads the capacitors. It is best to connect two capacitors in series with a voltage divider. Then there are no nasty surprises.

 

[Anyoldears]

What dac are you using Lampizator web page it says these rectifier tubes are compatible one rectifier DHD : 5U4G or 274B or 5C3S or 5Y3 or GZ37 or 5R4WGB with Baltic4

Pacific - as per the signature