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Old April 7th, 2010, 12:24 AM   #1 (permalink)
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274B rectifier tube...swap for a 5AR4? Hear of it? Done it?

I was poking around pricing some NOS tubes and what not and came across this concept - swapping a 274B (a big coke bottle shaped thing) rectifier for a 5AR4/GZ34. Apparently it will do wonders for tone. However, the application discussed turned out to be high end audio equipment. But I was wondering if anyone knew anything about this in a guitar amp circuit.

Apparently the NOS 274B was made by Western Electric and there's a few modern production including a cheap Shuguang version.

Valve gurus?

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Old April 7th, 2010, 01:18 AM   #2 (permalink)
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Looks sexy, but it's more of a 5U4 with a 200mA current rating. (5U4G is rated for 225mA, 5U4GB for 275mA.) Compared to a 5AR4, it'll sag and soften attacks quite a bit.



For the price, they're probably best displayed in a pretty-looking hi-fi rig than tucked inside a guitar amp.

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Old April 7th, 2010, 11:13 PM   #3 (permalink)
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The Chinese version is pretty cheap...they are cool looking. Wonder if they work.
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Old April 8th, 2010, 01:24 PM   #4 (permalink)
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Oakland, as SCott alludes to, the current draw is the big question mark. I generally adhere to the thought that a power transformer that is built for a GZ34 does not want to see a rectifier tube that draws higher current. Therefore, I do not substitute a 5U4 tube in a GZ34 application. I would hold the tube you are considering in the same light...higher current draw could put the PT at risk. I have heard a BFDR with a 5U4 running in the rectifier position....volume was much diminished, tone was non-existent. The owner had just purchased the amp and had not noticed the improper substitution. When I put a GZ34 in the rectifier socket, the amp came to life...the PT was not being drawn down by a basically improper demand. Luckily, the PT was not damaged. IF this tube you have has a current draw of 200ma, it is closer to the GZ34/5AR4 sepc of 175ma than is a 5U4, but I still would not advise using it in place of a GZ34.
A GZ34 can be used in place of a 5U4 with the only concern being that the GZ34 will yield higher voltage to the B+. The concerns are what the tubes will handle and does the player want the resulting sonics.
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Old April 8th, 2010, 04:14 PM   #5 (permalink)
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If the Chinese 274B has a 2-amp filament like the original, it would be fine. I'm suspicious that it's a re-bottled 5U4, though.
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Old April 9th, 2010, 08:38 PM   #6 (permalink)
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Guys, bear with me as my understanding of some of this stuff isn't quite there yet.

Some blurbs on this tube:

"The 274B tube is designed to supply direct current up to 200 milliamperes from an alternating current source. It comprises two filament type diode units with a common filament."

and from a hi-fi guy's blog:

"My best sounding one is the Mullard GZ34. It's one of those short stubby jobs that lives up to all of the hype that surrounds a Mullard tube. The GZ34 is warm, detailed and dynamic without sounding overblown at all.

Enter the Sophia 274B, ST bottle, solid plate rectifier tube. This is one extremely cool looking tube. It's almost the same height and width as the 2.5 volt 300b. The construction is a square plate though after checking the Sophia web site they are now offering this in a Meshplate also.

Apparently, this is a fairly fragile tube (electrically speaking). Richard at Sophia asked me to send him a copy of my schematic before I installed this in my system. He wanted to check to see the value of the first cap of the B+ voltage after the rectifier tube. In the case of the Handmade amp, it's 22uF. Richard recommends that the first cap be no greater than 10uF. In my case I ended up changing out the 22uF cap for a 6.8uf Solens. The reasoning behind this (as I'm told) is so the 274B doesn't have to work as hard pushing the current beyond this first cap. In turn you will receive a rectifier tube with long life and good reliability. I won't even attempt to explain what happens to the voltage and current downstream of the first cap, I'm not qualified. Though after checking with a couple of people that I trust, they said the sonic result of lowering the value of that cap should be fairly benign.

Doing some really critical listening between the two different tubes, there are some fairly audible differences. Going from the Mullard to the 274B, the most immediate thing that happens is that the soundstage opens up significantly. It becomes wider, deeper and taller. The performers take a solid one to two steps backwards. Next is focus. Where the Mullard GZ34 gives a very nicely rounded presentation of a performer, the 274B has tightened the spotlight on that same performer.

It's a bit hard to describe. I haven't lost any of the full rich sound of the Mullard but I've picked up (subjectively) a considerable amount of detail and focus with the 274B. Another byproduct is that the notes played have taken on another level of sharpness."


I barely understand about half of this...does it help you guys get a better read on this valve?
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Old April 9th, 2010, 08:52 PM   #7 (permalink)
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6.8uf first filter?! Count me out!

Gotta love the audiophool hype machine, if it's rare (because it was a short lived product quickly supplanted by a superior part), it's expensive (self explanatory) and it has the magic logo on it (like W.E.) it must be the wildest panacea on Earth for everything from halitosis to athlete's foot.

"They said the sonic result of lowering the value of that cap should be fairly benign."

Not in a guitar amp, it isn't.

"The most immediate thing that happens is that the soundstage opens up significantly. It becomes wider, deeper and taller. The performers take a solid one to two steps backwards."

Shoo-weet! Put that sucker in your amp, you'll have to re-adjust the stage lighting. Tell the followspot operator you'll be two steps further back during the show.
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Old April 10th, 2010, 02:12 PM   #8 (permalink)
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That fellow writing that hi-fi review should have to listenin a blindfolded test and tell us which tube is operating at what tiem. Then, I might accept whawt he has to say.
IME, when someone pays a lot of money for something like this, there is a great chance of expenditure-driven bias. The only way to avoid this is with a blind listening test....and I am sure this fellow did not do that.
I agree with muchxs about that small capacitance in the first stage. IF the 274 can
only handle 10mfds at that stage, then it is not meant to do well in a guitar amp, ime.
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Old April 10th, 2010, 02:22 PM   #9 (permalink)
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Quote:
Originally Posted by Wally View Post
I agree with muchxs about that small capacitance in the first stage. IF the 274 can
only handle 10mfds at that stage, then it is not meant to do well in a guitar amp, ime.
Seems like a big fat 5Y3, doesn't it? A 5Y3 is an adequate but by no means great tube IMO.

I'll betcha some hosepipe got hold of some of the dregs they hoed out of Western Electric's old building in Massachusetts not so long ago. I'm not sure if I have the story straight but Lucent bought the building, there was a bunch of stuff in the catacombs as well as a small museum of WE prototypes. It all went into the dumpster then into a garbage truck but not before a few "crows" picked some shiny trinkets off the top. The next step of course is to monetize the scrap by writing online reviews touting "Heavenly Tone."
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Old April 10th, 2010, 02:35 PM   #10 (permalink)
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much, if it is a 10mfd max rectifier, then it can't measure up to a 5Y3, which imho is a great tube when used in the proper circuit. Many great amps use a 5Y3 to great effect.

"Hey there, young man, come on over here and sample the greatest thing you have yet to encounter in your life. IF this doesn't do everything I tell you, then please see if you can catch me on down the road....don't matter which road.....just come and find me and I will guarantee your satisfaction with this product. HeHEhe.....lend an ear here. Don't you see how the soundstage has enlarged and become more transparent....why you can almost see through that girl singer's gown...but don't mind that, listen to the sparkling highs. Yessir, you are correct that her's do sit up high. Don't pay any mind to that distraction. LIsten for the dimension...it's taller, right? Fill's the upper reaches of your ear canals without a doubt. That's right, son.....this will do for you what nothing has ever done for you. NO, son, not the girl singer....the product, the product...its the product we're talking about. tHat there is my daughter, and she is simply exhibiting the product. KEep your mind on the deal, boy. Don't let things distract you, or you will buy something you don't need, you hear? NOw, back to the soundstage....."

SNake oil, son, its snake oil. Lubricates the wallet so as to facilitate the removal of greenbacks.
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Old April 10th, 2010, 03:17 PM   #11 (permalink)
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Quote:
Originally Posted by Wally View Post
much, if it is a 10mfd max rectifier, then it can't measure up to a 5Y3, which imho is a great tube when used in the proper circuit. Many great amps use a 5Y3 to great effect.
10uf first filter is "by the book" for a 5Y3, that and a relatively large voltage drop are what make a 5Y3 adequate but not great in my book. Of course if you have 4 amps on 5v winding not 3a you can use 2x 5Y3 and accomplish interesting things. But, shhh... don't tell the medicine show guys that! They'll want to sell you 2x fancy Western Electric rectifiers in matched pairs for 4x the amazing sonic effect.

Oops! Did I say that out loud?!

Let me de-mystify this for those who aren't following the tech joke banter:

6.8 uf is where your old Astron electrolytics end up when your amp is way overdue for a cap job. A small minority of technicians will use relatively small (6.8uf is tiny!) filter caps to "loosen" their amp up. It's generally not a good idea if you want to hear your low "E" string...

Quote:
Originally Posted by Wally View Post
Don't you see how the soundstage has enlarged and become more transparent....why you can almost see through that girl singer's gown..
I now appreciate enlarged and more transparent soundstage. Now that you've explained it to me...
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Old April 10th, 2010, 06:38 PM   #12 (permalink)
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Oh Wally and muchxs, it is not all that bad. 6.8uf PP as the first cap is going to have an ESR an order of magnitude lower and flater then an electrolitic and it will do find in an SEamp that never sees overdrive. In an amp that does see overdrive, you just have not take power from that node, and make the next cap bigger. It is all part of using your parts correctly.

Now is it a great tube for guitar amps? not likely. Is it a great HiFi tube? I will never know, I switched to SiC schottkys long ago and never looked back. Some day that technology will be priced so it makes since in a guitar amp, but not yet.
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Old April 10th, 2010, 08:17 PM   #13 (permalink)
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Oh Wally and muchxs, it is not all that bad. 6.8uf PP as the first cap is going to have an ESR an order of magnitude lower and flater then an electrolitic and it will do find in an SEamp that never sees overdrive. In an amp that does see overdrive, you just have not take power from that node, and make the next cap bigger. It is all part of using your parts correctly.

Now is it a great tube for guitar amps? not likely. Is it a great HiFi tube? I will never know, I switched to SiC schottkys long ago and never looked back. Some day that technology will be priced so it makes since in a guitar amp, but not yet.
Technical writing 101: Same as Music Performance 101, take stock of your audience. The OP's question was "Is this thing really superior to a 5AR4?" The short answer is "No, in fact it's relatively useless in any conventional guitar amplifier I can think of." It's like Minty and Sandy who work in the front office. Minty... yum, yum! Sandy... ptoo, p'tooey!

Mullard 5AR4 rectifer for guitar amps... yum.

Western Electric 274B for guitar amps... p'tooey!
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Old April 12th, 2010, 11:57 AM   #14 (permalink)
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I run 5U4GB Winged C's in my Delux Reverb and my Bonpicker Half Breed amplifiers, most of the Budda Amplifiers use these as well.
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Old April 12th, 2010, 10:44 PM   #15 (permalink)
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A comment or two...

To this -
Quote:
Originally Posted by muchxs View Post
The OP's question was "Is this thing really superior to a 5AR4?"
Um....actually I never asked that or implied that. The original question, paraphrased for clarity is, "would this tube work in a guitar amp and do so as well as it's alleged to in a hi-fi amp". The answer to this after a lot of tech jargon appears to be a solid no.

That's all I was wondering about. I know tubes work different in different applications...was just wondering about this tube. Clearly it won't work. End of story. I'll know if anyone asks me now.

And I wouldn't beat the hi-fi guy up too bad about the hype. We see it everyday on this forum re tone wood, caps, pickups, speakers, and yes...tubes.

Thanks for the responses.
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Old April 12th, 2010, 11:08 PM   #16 (permalink)
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Well, I wouldn't call it a "solid" no... I'd treat it like a 5R4. Keep the input capacitance light, and don't put it in an amp that needs lots of current. But then, the Chinese ones are cheap, so why not. There are less noble ways to have fun!

In my posts, I was mainly concerned about people buying genuine WE 274B's thinking they are going to do amazing things for their guitar amps!

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