Decware amps typically use between 33 ~ 47uf caps as the first section of the power supply filter after the rectifier tube.

In the case of the SE34I.3 the value is 47uf.

So far all the 274B's I've looked at ( and I haven't looked at all of them ) would like to see less than 10uf as the first section of the power supply filter.  Going beyond the value could cause flashing upon startup.  That said, many people ignore the warning and use it anyway, claiming the sound is worth the potentially short-lived tube.

Steve

I am curious as to how one of these mesh plate rectifiers sound. Would they be that much better than a good NOS 5U4G?

Anybody know what the cap value is on the Torii?

I've been following this particular thread with interest since I have a SE34I.35 on order. Unfortunately, while I love tubes I'm not well versed on the technicalities as they apply to safe rectifier tube rolling in the SE34I.3.

My understanding of Steve's 1st reply to this post, is that the SE34I.3 has a capacitor value of 47uf and he doesn't recommend using the EML 274B rectifier tube because, in his experience, many 274B type tubes want "to see less than 10uf as the first section of the power supply filter." Ignoring this fact could lead to premature failure of a very expensive tube. From Steve's point of view an EML 274B is not a safe tube to use in the SE34I.3, or any other Decware amp with higher capacitor values.

What I'm unclear about is whether the EML 5U4G mesh plate, which, according to EML's specs, wants "the first capacitor connected to plates to be 33uf" also falls into the same unsafe catagory. http://www.emissionlabs.com/datasheets/EML5U4G.htm  since the SE34I.3 uses a 5U4G rectifier at 47uf, albeit, not an EML mesh plate.

Does this mean that even though the EML tube is a "5U4G" tube that it can not safely be used in the "Rachael" which uses a 5U4G rectifier? If so, why? I'm confused about this.

Thanks Lord Soth for the analogy.

If I understand your analogy correctly, that means that we can not use an EML 5u4g tube spec'd @ 33uf in a Decware SE34I.3 integrated amp which has a 47uf cap. The tube would spark, which is bad and also voids the EML warranty. This, in turn, seems to mean that not ALL 5u4g brand tubes are electrically interchangable in an amp designed to use 5u4g rectifiers like the SE34I.3. This just sounds wrong to me. But, it still doesn't explain why any true "5u4g" tube would not be electrically identical to any other 5u4g tube and a "no worries" drop in replacement.

Is it the mesh plate design of the EMLs, or are variations in the spec perfectly permissible?

Looking at the Decware Factory Tube replacement page https://www.decware.com/newsite/tubesets.htm the Ruby brand 5u4g is offered, but no specs are noted regarding capacitor rating.

How disappointing. Say it ain't so Steve.

Yes.

In the old NOS days, there was an industry standard which major manufacturers adhered to.

The new vacuum tube manufacturer has deviated from the industry standard for 5u4g rectifier.

The old NOS tubes made by major manufacturers such as Tung Sol, Mullard or Telefunken were often designed to be able to take more punishment than their official specs. Hence they are more rugged than new production tubes.

The EML is overpriced to me.

At those kind of prices, I'd rather get a trusted NOS tube.

BTW, I suggest trying the Philips 5R4GYS from upscale audio as a replacement for your 5U4G rectifier. It only costs $45. There are glowing reviews over there and I have experienced it for myself.
If that works out for you, the Brimar 5R4GY will definitely sound even better in your setup.

I finally ordered the philips rectifiers and reading L Soths observations
in the above were very helpful in decision making. In fact I`m getting
warmed to the Philips brand. The miniwats always look enticing.
Riz, I did read that a user of the EML got 600 hrs out of the tubes before they went on the blink whereas they should last 1000`(s) +. So you could take a flier, if it`s just the tubes that go and no damage elsewhere....
In the info they provide they mention some component changes inside the amp and also they had to change or add extra heaters because of problems. I think if you wait they will eventually fix all the bugs.
Lotta money for a punt.

My mind is melting with this 5U4G rectifier issue.

I just went back to the EML 5U4G technical spec page. As I posted yesterday (Reply 7 & 9), EML spec'd their 5U4G at "33uF for 1st capacitor connected to plates" (that was on Jan. 11, 2013).

I also posted the email response I received from EML's Jac van de Walle where he confirmed the EML 5U4G had a max capacitor value of 32/3 uF and the 5U4GB (an electrically different tube) was 40 uF (see my Reply 12 this thread).

This evening, Jan.12, 2013, I went back to the same EML spec page and guess what, EML changed the max safe capacitor value for the 5U4G from 33 uF to 40uF! I sure wish I had saved a copy of yesterdays EML 5U4G web page. So maybe they caught an error because of my inquiry and fixed it? Fair enough.

But, according to Mr. de Walle's email of 1/11/13, the 5U4G and 5U4GB are electrically different tubes, so how can they have the same capacitor value when he stated different values in his email to me? Perhaps another error regarding the 5U4GBs correct max capacitor rating?

As Mr. de Walle's email also mentions, the photo of the SE34I.3 on the Decware site shows a 5U4GB rectifier being used.

So as Dr. Szell (Laurence Olivier) asked Dustin Hoffman in "Marathon Man": "Is it Safe?" the EML 5U4G that is.

P.S. I'd prefer not to have my teeth probed without anesthetic on this one.

Clowkoy, my apologies in advance for this long winded reply. It's more, or less, a summary of everything I've said before and where, in my thinking, I'm at now on the subject. I'm hoping it will be my last post on the subject.

Quote:


Clowkoy, the problem to which you refer (rectifier tube/amp compatibility) IMO, is not just my problem, it's a problem for anyone who owns or contemplates purchasing a Decware SE34I.3 and contemplates tube rolling. At this point, at least for me, the jury is still out on whether it's the amp or the particular tube that's at the rooThere is no mention of any other type of 5U4 tube, i.e., 5U4GA, GBt of the problem in the first place. This is assuming there is a problem at all! Until I hear more from Steve, I shall reserve judgment. (skip to the last paragraph if you don't care to read any further)

As for replacing caps, that, IMO, could and probably would void the lifetime warranty, not to mention compromise Steve's intended design goal for this amp. While I may be somewhat ignorant about the internal workings of tube electronics, I get the feeling that changing a cap in a preamp is less problematic (read dangerous) than doing so in a power amp.
There is no mention of any other type of 5U4 tube, i.e., 5U4GA, GB
In the end, I have to believe that Steve knows how to build a proper amp for the tubes he selects and that he knows how to select caps with proper values so that those tubes operate correctly, within their intended specifications (NOS or current tubes), and without flashing issues (all this, notwithstanding what EML's Mr. van Walle implied in his email to me yesterday. See Reply #12 above).

Carefully reading the the Decware web site "Specifications" on rectification for the SE34I.3:

Quote:


There is no mention of any other type of 5U4 tube, i.e., 5U4GA, GB
and the pdf "Owner's Manual" for the SE34I.3 "Rachael":

Quote:


you now know the following:

1. the substitute rectifier tubes which could be a problem are some 274B's. A list of know problem 274B is not given;

2. the 5AR4 or 5Y3GT tubes are compatible substitutes for the 5U4G; and

3. any "5U4G" tube will work (NOS or current) since there is nothing in the manual or spec that states otherwise similar to the caution on the 274B. There is no mention of 5U4GB which is not electrically the same as a "5U4G", although, I think, it does appear to be safe to use from everything I've learned so far. We need Steve's confirmation on this.  

What set me off on this journey was the OP's original question concerning "safe" rectifier substitutions for the SE34I.3 "Rachael". The OP wanted to know if it would be safe to substitute a 274B in place of a 5AR4/GZ34 AND his important notation of flashing problems in WOO amps which used the Sophia 274B and EML 5U4G.

To be clear, nowhere in this tread has it been stated that an EML 5U4G will flash and prematurely fail in the SE34I.3. The closest anyone in this thread has come to "suggesting" premature failure for the EML 5UG4, was "Marky" in replies #10 and 15 concerning what he read regarding the EML 5U4G tube on "other" forums, possibly with other non-Decware amps.

Nevertheless, the only reason I posted anything in this thread was because of the warning about tube-flashing of "EML 5U4G" tubes. I asked myself: why would the EML 5U4G flash in a Decware "Rachael" which is designed to accept a "5U4G"? By "a 5U4G" I am only referring to that specific tube, not to 5U4GA or 5U4GB.

When I looked at the EML 5U4G max capacitor spec on the EML web site, it was originally noted to be 33 uF and in less than 24 hours was quickly changed to 40 uF (as I noted in a post above). Both of those values were below Steve's selected cap value of 47 uF. Was this a potential flashing problem? Maybe. Lord Soth's "ballon" analogy in reply #8 on page 1, which explains how a tube can be stressed when used with a capacitor rated higher than the tube's max capacitor specification added to my concern. Adding more confusion, was the fact, pointed out by EML in their email to me, that the picture of the Decware SE34I.3 showed not a 5U4G, but rather a 5U4GB, an electrically different tube with a 40 uF cap rating. The 5U4GB is still 7 uF below the SE34I.3s 47 uF cap. Is this a problem or not?

Recognizing that tubes are tempermental beasts, and can fail at any time and for almost any reason, I am at the point of asking the following questions:

1. If the 5U4G and 5U4GB are electrically different tubes, are they safely interchangable (NOS or newer current types) in the "Rachael" in the same way 5AR4s or 5Y3GTs are safe substitutes? If not, why not?

2. If the "Rachael" is using a 5U4GB as the stock tube, rated at 40 uF max according to EML, why isn't this noted in the specifications to avoid confusion?  Steve has confirmed in an email that the rectifier he is using (without exactly specifying the model tube) is working without issues, but he can't confirm that the EML 5U4G will work because he has never tested it in the Rachael. Excluding a bad tube, why wouldn't an EML 5U4G work properly? It seems to me the specifications should state which of the 5U4 family of tubes is safe to use.

So, in the end, I believe what is needed for the SE34I.3 is more and clearer information from Steve himself. Much akin to what he provides for the Mini Torii information page (pictures and descriptions of all the compatible tubes).  

This is asking questions about tubes that I haven`t got involved with on the spec sheets.
I`ve bought 12ax7`s, 12au7`s, 5u4`s, 5y3`s, 5ar4`s, and 5r4`s with all sorts of different suffixes....I just buy them put them in. So far no prob.
When I read here about the 247b`s I thought wow, yeah, must get one, they`re huge. But...they came with baggage, as in the brightest light burns half as long..possibly. I still check them out, out of curiosity. Then a couple of months ago the mesh rectifiers were mentioned. I couldn`t find them until Rizlaw brought them to light. I thought they would be old NOS at just a bit more cost but they`re new and 3-4 times more expensive.
I must say I was hoping someone would say " Oh, I use them and ...."
Are they the only makers of mesh 5u4`s ?
How new are the mesh tubes ?

There are infamous tube equipment which literally eat tubes.

AFAIK, Decware amps are not designed like that.

The cap values used in their amps is pretty standard and tube friendly so you can literally pop in any of the standard NOS rectifiers such as 5Y3G to 5R4 to 5U4 to GZ34 .... Etc. Those few uF will not make any difference so quit ya yammering will ya?

BTW, the ultimate rectifier is a GEC U52 or the Western Electric 274b.
These have a lower maximum uF cap rating than the standard 5U4, 5Y3 rectifiers used today. I believe that Steve designed his amps to sound fantastic based on good old American made standard rectifiers which were (and still are) cheap and easily available.
Case in point is the CSP2 amp, the US$20 5y3 sounds fantastic in this tube amp.

The cap values also have a bearing on the final sound and so based on what I've mentioned above, I don't see any fault with Mr. D's designs.

If you still insist on using one of those mesh rectifiers, I'd suggest opening a dialogue with Steve to specially accommodate that. The famous Woo Audio also made a special version of some of their amps to accommodate exotic rectifiers like the mesh plates.

However, your final sound output will be different from the original design a.k.a Mr. D's "vision".
The final sound could be better or worse.

LS,

For the record, nothing I have written casts any doubt on the quality of Steve's designs (that was something EML's Jac van Walle seemed to imply in his email to me if his tube didn't work in the "Rachael." He ultimately felt it should work). I wouldn't be ordering a fully optioned "Rachael" if I had doubts.

And yes, I've already quit my "yammering" (although, I thought that what I wrote was better than simple "yammering", perhaps more like "kvetching" when something is not clear enough.

BTW, I thought you rated the Brimar 5R4GY rectifier #1 and the Philips 5R4GY #2 in your shoot out? I just checked, TubeDepot has the WE 274B for a mere $999.00, which, I imagine, is a non-starter for all but the most prosperous hardcore tube-o-philes.http://tubedepot.com/nos-274b.html

Do you promise, by all the pixie dust in NeverNeverLand that those few uFs won't make a difference.

Hi Rizlaw,

Yes, I'm positive that you can safely use any NOS 5Y3, 5R4, 5U4, GZ34 rectifiers in Decware amps. Within each of the major families, there will be a slight variation in uF, e.g. 5U4G vs 5U4GB. This is perfectly fine.

The WE 274b and GEC U52 are really out of the "safe" range wrt uF.

The Brimar 5R4GY retails for around US$100 whereas the Philips 5R4GYS costs less than half of that. From my point of view, they are both Military grade tubes which should be able to last at least 10 years, so the cost is reasonable.
New vacuum tubes don't last as long, hence my personal adversion to forking out 200$++ for the mesh plates.

Now it's me who's doing the yammering.

And I listen to Mr. Steve D.

;)

Steve,

Thank you for removing my veil of confusion about this as it regards the "Rachael". I have three more questions:

1a. Notwithstanding cost, which is considerable, does the same caution you give for the mesh plate EML 274B rectifier apply equally to the mesh plate EML 5U4G rectifier with a (40 uF max cap value)?

1b. Does it have something to do with "mesh plate" type tubes, or has it more to do with current tubes vs. NOS tubes?

2. Apart from the two rectifiers (Sovtek 5Y3GT and Ruby 5U4G) you offer, are there other NOS or Current new tubes) in the tube groups you mentioned that have been found to work well with the 47 uF "Rachael"? If so, listing a few would be greatly appreciated?

Again, Steve, thanks for the clarification. I want me "Rachael" straight, thank you.

Congrats Rizlaw. Hope you get that hum issue "rectified."

Anyway, a headphone jack, eh? I had said all the Rachael needs is a headphone output to be the perfect integrated amp. Sounds like a great rig.