Forums - Safe rectifier roundup (Decware input pending)

hifitubes

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Posts: 75

Safe rectifier roundup (Decware input pending)
07/04/12 at 07:49:22

Preferred Series 274B

The Preferred Series 274B tube is a full-wave rectifier that is very similar to the classic 5U4G. This 274B tube's filament draws 2.5A of current. This current draw makes it acceptable for many amps originally designed for a 5AR4/GZ34 tube. Our PS-274B tube is a beautiful large coke bottle shaped rectifier tube with large black plates. Space may be an issued in some amps so be sure to check this.

Note - ISSUES REPORTED WITH WOO AMPS The tube emitted flashes, it turned out the first cap value is 330uF which is a lot higher than what is required to run a Sophia 274B or EML 5U4G.

GZ32

(5V4G=83V, GZ32=5V4G, 5V @ 2.3A Filament, PIV=1540V, Imax=175ma, Max Capacitance=60uf)

The 274B should be okay as should be the GZ32 imo.

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« Last Edit: 07/04/12 at 11:28:03 by hifitubes »

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Steve Deckert

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If the 1st watt
sucks why continue?

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Re: Safe rectifier roundup (Decware input pending)
Reply #1 - 07/05/12 at 18:38:32

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

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hifitubes Senior Member Posts: 75	Re: Safe rectifier roundup (Decware input pending) Reply #2 - 07/07/12 at 05:59:06 Thanks Steve. The EML 5U4 mesh plate spec. is: max value for capacitor, connected to plates - 33uF. Interesting as some GE data sheets show 40uF for 5U4 as typical. thanks jon
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Rivieraranch Seasoned Member Posts: 1109	Re: Safe rectifier roundup (Decware input pending) Reply #3 - 07/07/12 at 13:33:41 I am curious as to how one of these mesh plate rectifiers sound. Would they be that much better than a good NOS 5U4G?
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orangecrush Seasoned Member Posts: 149	Re: Safe rectifier roundup (Decware input pending) Reply #4 - 07/07/12 at 16:28:49 Emmision labs state either a max capacitor of 33uf or choke loaded. Don't most Decware Amps have chokes?
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orangecrush Seasoned Member Posts: 149	Re: Safe rectifier roundup (Decware input pending) Reply #5 - 08/04/12 at 19:12:27 Anybody know what the cap value is on the Torii?
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Les Lammers

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Posts: 137

Re: Safe rectifier roundup (Decware input pending)
Reply #6 - 10/15/12 at 17:45:33

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

At $240 each it would be an expensive coin toss.

I have quite a few 5U4G's and will put them on the classifieds soon. I've had them for years and will likely never use or need them. I'm a recovering tubaholic. ;)

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Rizlaw

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Posts: 38

Re: Safe rectifier roundup (Decware input pending)
Reply #7 - 01/10/13 at 16:42:13

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.

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« Last Edit: 01/10/13 at 16:43:54 by Rizlaw »

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Lord Soth

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Re: Safe rectifier roundup (Decware input pending)
Reply #8 - 01/10/13 at 17:30:13

To use an analogy, think of the max uF of the rectifier as blowing up a balloon. Every type of rectifier has a max uF limit specified in the tube data sheet. If the amp uses a higher uF than the maximum limit of the tube, you are over blowing the ballon and over stretching it. This stress will cause the ballon to explode.

Ermmm, hope that helps.

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Rizlaw

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Re: Safe rectifier roundup (Decware input pending)
Reply #9 - 01/10/13 at 17:58:18

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 http://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. Cry

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marky

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Posts: 132

Re: Safe rectifier roundup (Decware input pending)
Reply #10 - 01/10/13 at 18:28:01

I understand the point. Seems like all the old NOS 5u4`s were similar spec and the EML comes along, same...but different...but why ? They must be aimed at a particular amp family. I see they dont make a mesh EL34 but do make a mesh 300B and 2a3. Could be the clue.
I`ve been reading a few forums on them and it`s the same story, if you use them they wont last long with the 47uf.
I`m interested because I still haven`t decided what pair of rectifiers to go for on 2 Rachaels.
So far I`ve bought old nos Tesla mil EL34`s and b/boy 6dj8`s.
Not to expensive so far. The EML`s would seem like overkill. :)

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« Last Edit: 01/10/13 at 18:33:09 by marky »

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Lord Soth Seasoned Member I'm an American BadAss! Posts: 110	Re: Safe rectifier roundup (Decware input pending) Reply #11 - 01/11/13 at 03:14:06 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.
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Rizlaw

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Re: Safe rectifier roundup (Decware input pending)
Reply #12 - 01/11/13 at 20:08:45

Lord Soth,

You may be correct on this, but EML's data sheet for the 5U4G makes it clear, or so I think, that the tube "is a direct replacement for the historical 5U4G" http://www.emissionlabs.com/datasheets/EML5U4G.htm notwithstanding the 33uF upper limit. I suppose the question is, what do they mean by "historical". They provide old chart info at the bottom of the data sheet which I don't even begin to comprehend.

I have sent an email to Emission Labs asking them to clarify if their 5U4G is suitable for the SE34I.3. I hope they respond favorably. I sent a similar email to Steve and he responded very quickly: he' can't say for sure because he has never used the EML 5U4G.

EDIT 1/11/13, 6:00 pm:

O.K., I just received EML's response to my email this afternoon.
Here it is in bold type:

"the 5U4G is originally specified for maximum 32uF.
5U4GB is 40uF. You can recognise it by the cilinder glass.

I see this amplfier pictured with 5U4GB. There are
often cases people are not aware of the
difference between 5U4G and 5U4GB.

So if someone uses 47uF that is out of specifications, and
the limit is 33uF.

One should not design an amplifier by "not having trouble"

If it is wrong, it is just not right, and that is where
we are with 47uF.

For cost reasons, you do often see this 33uF exceeded,
but it's a not so nice game, and it's on the risk of the
owner. We have to deal with amplifier builders who
know this, and some who don't know this. Both are
not easy to deal with. The Decware SE34I.3 never
had any problem reported, so I suppose we should
leave it out of the problem list. I think probably it will
work, this is just my feeling. But it's on you own risk.

You can ask any of the NOS dealers if they will
replace a broken RCA tube you used it one year
in some small overload condition. I don't think they
do that. Guarantee is only very short on NOS tubes.

However at EML we want to give you one year guarantee,
but that requires correct use of course. Sorry for
being the bad guy, but good use comes first. I hope
you understand it.

Best regards,
Jac"

So, I guess if anyone tries it, and it fails, you're out $230.00. Cry

BTW, in the 2nd paragraph of his response, I think he is referring to the picture of the SE34I.3 with a 5U4GB rectifier on the Decware "Amplifiers" homepage. If you blow up the image, you can see a 5U4GB straight bottle tube. I was a little surprised by this, but I don't think its an EML tube because EML doesn't make 5U4GB tubes.

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« Last Edit: 01/11/13 at 23:21:00 by Rizlaw »

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Lord Soth

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Posts: 110

Re: Safe rectifier roundup (Decware input pending)
Reply #13 - 01/12/13 at 01:55:59

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.

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Rizlaw

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Posts: 38

Re: Safe rectifier roundup (Decware input pending)
Reply #14 - 01/12/13 at 03:32:11

Lord Soth,

I agree the EML is expensive, but it looks beautiful and it is hand made. The EML would visually complement the Treasures I've also ordered from Steve for the Rachael. Genuine NOS Brimars or RCAs are at about the same price points as the EML at most of the online tube retailers, if and when you can find them!

I spent a few hours surfing the web today for 5AR4 variants and I came upon a thread on Upscale Audio's website which pointed me to your mini-rectifier-shootout. http://www.audioasylum.com/audio/tubes/messages/24/248138.html Nice work and helpful.

Since my "Rachael" won't be ready for, at least, another 8 weeks as far as I can guess-timate, I am reluctant to buy a couple of those Phillips rectifiers since I have no way to test them until the Rachael arrives. I'd hate to spend $$$ now and find out 2 months from now that what I bought was damaged with no recourse. Upscale only offers a 30 day warranty. I'll have to hope they are still available when I'm ready.

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