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NOS tube questions (Read 1303 times)
derekinla
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NOS tube questions
08/31/21 at 04:52:08
 
I recently placed a deposit for a Torii Jr and am interested in starting to compile some back up tubes to have in anticipation. I purchased two RCA 5U4GB NOS rectifier tubes from vintage 1965 for about $20 a piece on EBay.

1) Is there a big difference between 5U4G vs 5U4GB in terms of impact sound, or longevity of the tubes? I ask as there are way more 5U4GB‘s than 5U4G’s on EBay. The GB variants are also way cheaper. Unless there is some compelling reason to get the 5U4G, I presume I’m good with the GB’s.

2) I am looking to get some 6N5P input tubes and all I see are NOS Russian tubes on EBay. I’m guessing these are fine? Do the 6N5P’s have to be a matched pair ?

3) my impression is that the OA3 regulator tube will probably the longest lasting tube on the amp since it operates at a much lower temp. Is that correct? Is it worth getting back up(s) of these?

4) Any reasonably priced brand recommendations for the EL34 output tubes?

Thanks
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GroovySauce
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Re: NOS tube questions
Reply #1 - 08/31/21 at 12:57:41
 
For the rectifiers. 2 RCA 5u4GB will in theory last you many years. Yes there are differences between the 5u4GB and 5u4G. My 5u4GB's are from the 70's and my 5u4G's are from the 40's so that's also a factor.

I suggest looking at also trying a 5AR4 it will have a dramatic effect on the sound.

OA3's should outlast all the other tubes. grab an extra pair, it's good to have backups of tubes. You can also try OB3's or OC3's drastic change in sound and power output of the amp.

For the 6N5P YES matched pair and matched sections / triodes, AFAIK 6N5P is a Russian designation. Chinese may have made some, I would stay away if you do see any Chinese made. Other tubes to try are: 6922, 6DJ8, 7DJ8.

I liked the Tung-Sol EL34's that shipped with my amp. I do prefer kt66's and kt77's over the EL34's  I like the GL kt77's they are on the spendy side.
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Lon
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Re: NOS tube questions
Reply #2 - 08/31/21 at 14:08:03
 
You have gotten good advice from GS. I say let the stock tubes season in and give you a good experience with the "base line sound." The most important tube to replace is the rectifier and you have that covered. The other tubes are going to be a good solid sound to experience til they start to age. I do agree that it is fun to experiment with the rectification tubes--in one decade or so I went from 0A3 to 0D3 to 0B3 to now 0C3 as my daily tubes! Each tube influences the other so there are so many possible configurations and you'll not get bored with these amps as you can subtly and strongly alter their overall sound just by tube-rolling. Still, what Steve sends has little wrong with it other than as he mentions himself the reliability of the rectifier.
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CAJames
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Re: NOS tube questions
Reply #3 - 08/31/21 at 20:58:11
 
The big difference between 5U4G and 5U4GB is the GB is a more recent version, 5U4Gs are older and have the (sexy) "coke bottle" shape. Old is generally better for vacuum tubes so the Gs tend to command a higher price. Electrically they are the same, but, as GS notes, that doesn't mean they sound the same.

Just FYI/FWIW I'm a big fan of the 5Z3 which is a 5U4G tube but with a 4 pin base. You can get adapters from ebay, and in general you can find a lot of great 5Z3 tubes from the 40's and early 50's (the golden age of tube tech) for a less $$$ then the 5U4G version of the same tube.
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derekinla
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Re: NOS tube questions
Reply #4 - 08/31/21 at 21:12:15
 
Thanks of the info guys. Will look into the 5Z3 tubes.  :)
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Tony
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Re: NOS tube questions
Reply #5 - 09/02/21 at 00:01:45
 
You can get adapters from ebay, and in general you can find a lot of great 5Z3 tubes from the 40's and early 50's (the golden age of tube tech) for a less $$$ then the 5U4G version of the same tube.

Hi CAJames

Knowing absolutely nothing about tubes, when someone shops on ebay for an adaptor, is there something specific you ask or look for?  Is an adapter generic?  Thanks.
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CAJames
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Re: NOS tube questions
Reply #6 - 09/02/21 at 02:06:46
 
Hi Tony,

Assuming you know "absolutely nothing" about tubes I'll answer like this. There are many types of adapters for sale on ebay, so you need to find the one that adapts the tube you have, in this case a 5Z3 to the tube your amp expects, a 5U4G. In short search for "5Z3 to 5U4G adapter."

Once you have that you will still see many adapters, that have 4 holes on top and 8 pins on the bottom, and they are more or less generic. But for me personally I always buy adapters from xulingmrs I've had really good luck with them.
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Tony
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Re: NOS tube questions
Reply #7 - 09/02/21 at 05:01:55
 
Got it,  that makes sense. Thanks
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derekinla
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Re: NOS tube questions
Reply #8 - 09/02/21 at 19:53:25
 
CAJames,

Just ordered the adatper from xulingmrs. Also picked up a NOS National Union tube from the 1940's. Thanks for the tip!
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CAJames
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Re: NOS tube questions
Reply #9 - 09/02/21 at 22:06:32
 
Good stuff. I love my NU tubes!
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derekinla
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Re: NOS tube questions
Reply #10 - 09/02/21 at 22:17:28
 
There is so much experience and wisdom on this forum! We should leverage that and create a forum crowsdourced open source tube rolling guide. Using something like google docs, the members of this group could create a centralized source of information for newbies.
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will
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Re: NOS tube questions
Reply #11 - 09/03/21 at 00:14:59
 
I have been into tuning so much, and so long, my preferred envelope is probably relatively narrow, and perhaps somewhat subtler stuff sounds big to me???

That in mind, I like variety within this envelope, and have been testing a bunch of 5U4s the last several days, the first rectifier I got into more extensive exploring with quite a long time ago ... I started with a smallish bottle RCA 5U4GB I recall trying because Lon liked them back then in his room. The particular tube I got was notably weighted toward bass, and my room, with Bob's MG944s and the Torii III (both designed for big bass), this particular tube tended toward an overly thick/full bass, so a bit too thick/muddled, while darkening the mids, and the highs were recessed, not cutting through the bassy veils very well...

Bad combo for me, this was compared to the stock Ruby 5U4G-ST that came with my very early Torii III, and some reproduction JJ and Sovtek 5AR4s. The Ruby was pretty neutral and open to me, but a little thin and uninteresting, and the 5AR4s were more potent....fast/dynamic, with bold tight bass, articulate, and spacious, tubes I used mostly then.

Then I found a late 40s Raytheon 5U4GB with a two step base made to accommodate a fat/straight bottle, black plates, and top/side horseshoe getters on both sides. Seems most fat bottles, the glass narrows on the bottom to fit into a narrower bass, so this tube caught my attention as unusual, and early. Still weighted toward bass in the balance, but also nicely dynamic and really good at fine detail and space.... and having finally found 5AR4s a little in the face on dynamic hit in my system/room, these were interesting to me. The bass needed some adjustment with some leaner tubes elsewhere, but then, instead of dark, I would call this tube "warm" having good space and detail within its dark leaning sound, even slightly euphonic, the complex warmth having a sweetness.

Chasing more 5U4GBs, I ended up with several really good sounding ones (to me). And who knows, with the better ones, I might still be using them had I changed back then to more open OC3s, but I only had warm/smooth OC3Ws at the time, nice tubes, but with two baseline tubes tending darksish, I didn't get into these OC3 with the 5U4GBs. Though I never liked OA3s... too forceful in my setup, there was something about the slightly milder/more open, and generally smoother feel from OB3s I loved here, so I tended to stay with them mostly for years.

The other day, starting these tests, I had been running sophisticated and supple sounding mesh plate 4V, 4 pin RGN-1064s (a Tesla still in the CSP3), at the time with OB3s in the heavily modified Torii IV. Though my system and room are much more refined, balanced and resolving than during my first foray into 5U4GBs, for me, they were still tending too dark, thickening/slowing the bass too much (especially on recordings leaning that way), and in turn masking the mids a bit much. A really good sound, but I need open space and relative neutrality, with tight/fast bass, complex detail, and within a mild warmth. So I put in my current fav OC3s that I actually have been using most in the last year, and they did a lot to balance the 5U4GBs in my system.... more open, textured, spacious, less bass thickness....now most seem to work on most recordings here (an important tuning standard for me) though still it is comparatively a darkish, yet resolving tube here.

I ended up gravitating to fat bottles and tall/fattish bottles, most with laddered black plates. All sound different, most good in my setup if you like that "flavor." Overall, they are notably powerful sounding dynamically, and tending bassy, but with the right company, reasonably tight bass, open/textured mids, and pretty complete detail with most of them..... and most are slightly euphonic without being syrupy in my system/room.

In early quests, seeking something similar, but less weighted toward bass, I found some value NOS RCA 5U4G-STs with a top/side getter, and this tube was more neutral, less forward, with more fine detail complexity, and pretty smooth in general...sort of like a sophisticated, fleshed out Ruby. An interesting change, I started watching for them. A few I tried had a little bigger/heavier black plates and bottom getters, nice also if the system needed more bass, but a little full/dark/solid here. Whereas the slightly lighter build plates and top side getters are more neutral and open here...maybe later 50s and early 60s models??? But finally these tubes ended up a little predictable to me they were so dependably relatively neutral in most every balance.... not much sticking out, not necessarily a bad thing, but I prefer a tube now that sucks me in more with a little more characterful complexity.

Comparing the famous '55 Winged 5u3Cs today (5U4G-ST equivalent), the Russian tube is similarly warm as some of the nicer 5U4GBs, but in comparison, has less speed, hit, detail complexity, and spaciousness, so not as alive and engaging to me. And though bigger warmth is not my thing in general, I do like a taste of it that is not particularly obvious, as long as the darker hue is relieved by good detail complexity that is not too recessed. These particular 5U3Cs are definitely warm, and the understory relatively balanced within that. But they are slow enough to feel veiled and lacking in fine detail for me.... Maybe the appeal of this tube has to do with more sharp system/rooms... don't know but lots of folks love this tube, so guessing different needs.

I have not tried 5Z3s, but by reports these are in the range (and look) of the 5U4G-STs, but generally quite a lot cheaper, the oddity of needing adapters presumably helping to keep them that way so far.

So that is a little 5U4 view from my room today anyway... hope it is of some use. I am enjoying playing with 5U4GBs...

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derekinla
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Re: NOS tube questions
Reply #12 - 09/03/21 at 01:50:49
 
Thanks for the detailed response Will! It is fascinating to hear about your experience combining the different 54U variants with the different regulating tubes to get different synergies and coloration of sound. So many variables to explore! Is my understanding correct that as you go from 0A3, to 0B3, to 0C3 tube (0A3 = 75 volts, 0B3 = 90 volts, 0C3 = 105 volts), there is a decrease in power output from the amp? In a 20 watt ToriiJr, how much off decrease in power would there be using an 0B3 or 0C3 tube?
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will
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Re: NOS tube questions
Reply #13 - 09/03/21 at 03:10:01
 
Yes, the way I understand the voltage numbers for VRs, they are voltage drops, so the OC3 drops the voltage more than OB3 or OA3, reducing voltage feeding the tube stage they filter. I am not up on how this works with the Junior, but with the MKIV, there is a regulator for both input and output tubes, the O_3s filtering the power tubes, and O_2s the input tubes, where the Junior has one.

And I don't know how to check how these adjustments change output power, so can't say how much.... but this does appear to lower overall power to some degree in the MKIV. What I like is the tonal adjustment, more voltage drop sounding like it pushes the tubes less hard, so opening the sound, and less drop making them more full and intense. A really good tool here.

Hopefully someone with more knowledge can help us with your question!
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All Modified: Power-PSA P5, Brickwall/Shunyata Defender>RevolutionMacMini/PureM>Kitsune Singxer/Gustard x20pro or NOS Tranquility DAC; CSP3, ZRock2, Torii IV, HR1, DIY ZBIT; Cables DIY: PCs, ICs, USB, I2S, Speaker; Feet- Archie's platform, alum/ball bearing, SR+
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dvl
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Re: NOS tube questions
Reply #14 - 09/03/21 at 21:14:59
 
i have had a Jr. since it first came out (2015?) and have had it modified twice, once with full anniversary mods and then up to version 2. i have played with several tube types over the years. Here's what i have found.

As far as OA3s go, they do last a long time if you let the amp run for 20 minutes every time you turn it on. Steve notes in the manual that it takes that long for them to stabilize and leaving them on that long helps their longevity. i have tried OB3s and OD3s. Didn't hear a lot of difference with the OB3s, but i did hear a significant difference with the OD3s. Steve states in the manual that OD3s can lower the output to 6-8 watts, but you may get better sound, particularly with a horn loaded speaker.  i found them to produce a more transparent sound, but a "thinner" sound. The bass and mid bass were not quite as full. i prefer the 0A3s.

i have tried a few different rectifiers, RCA 5U4Gs, both smooth plate and ribbed, Russian 5U3Cs, both black plate and gray plate, a Genalex GZ34, Sylvania 5Y3W, a Raytheon 5Y3, when i bought my amp it came with a Valve Art 274b, have also tried the Tube Store preferred series 274b, and a few others i can't quite remember at the moment.

To my ears, with EL 34s, the smooth plate RCA 5U4g sounded the best, but those have gotten rare and pricey. My next preferred is the black plate 5u3c. It is smoother on top than a ribbed plate RCA, and the bass it puts out continues to impress me. The gray plate 5U3C does not sound as good to me.

For power tubes, my favorites are the Gold Lion KT77s, and some good Mullard 807s. Back when i had to bias the power tubes, (you don't have to any longer with version 2 of the amp), i couldn't get the bias into the proper range with the 807s with any other rectifier than a 5Y3. That's why i tried them! i am currently running 807s with a Sylvania 5Y3W. Any other rectifier i have tried in version 2 produces an unacceptable hum. 807s produce a "sweetness" to the sound without reducing transparency or dynamics that i really like.

That said, the amp with Gold Lion KT77s with a Russian 5U3C sounds big, smooth, transparent and alive. Both sets of power tubes make me smile with the right rectifier!

i keep a set of Tungsol EL34s as a spare quad so when my power tubes get tired, i have a back up that will serve me until i get a fresh set of tubes.

For input tubes, i have tried a lot! Too many to remember. What i've settled on at the moment, and this may change, is 6N23ps from the Reflector factory. These are getting a little a pricey as well, so i may move to some 6N5Ps when my current input tubes get tired.  

i have written this elsewhere, this amp is just FUN. i have had so much fun listening and rolling tubes with amp, more than any other amp i have owned. i think you're going to love it!

David




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Dana
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Re: NOS tube questions
Reply #15 - 10/07/21 at 18:47:27
 
According to the SE84UFO manual
The volume control should be all the way down (counter-clockwise)
whenever the amplifier is first turned on and then slowly raised to the
desired listening level.

I'm not consistent doing this and noticed that the rectifier sparked (one big spark when it was warm and I was tube rolling) when I forgot

Is this the key to extending the life of the rectifier tube?

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will
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Re: NOS tube questions
Reply #16 - 10/07/21 at 19:41:42
 
As far as I can tell looking at my amps, both VRs and rectifiers are power supply tubes that feed power to the signal tubes, so I suspect warm up on these is a different thing than signal tubes where the volume effects what is happening in the tubes. And I wonder why these instructions are in your manual... I just don't know. I never turn down my amps before starting them, and I wonder if this instruction perhaps has to do more with initial use as you first start your amp in a system???

I have a few rectifiers that spark on startup when the amp is hot, but not on initial startup with the the amp cool and the caps discharged. These are RGN1064 and AZ1s, and it is only one of a pair, and the same one of each pair, the other not sparking. The same one sparks when changing channels too, so thinking it is the tube rather than possible electrical imbalances between channels.

These tubes are rated for big power supply caps, but are 4 Volts rather than the 5 volts these amp circuits have. They are also both mesh plates with pretty delicate seeming upside down V shaped cathodes. And both pair have been in for extended times (one for several years of heavy play...like 5-10 hours a day most days, and a lot of off and on with many progressive modifications happening, though I do discharge the caps before working in there).... and no blow outs yet. So I can't say in my case if it is the construction or voltage, or age, or all.... they are from the 30s and 40s.

On the other hand, I have had a number of times over years where "normal" 5 volt rectifiers might spark or flash on cold start up, and if I am remembering correctly, it got worse, sometimes quickly and sometimes slowly, but ended up blowing.

Having had it happen both ways, I don't know what to suggest in terms of your tube perhaps being near death..... Does it happen to be a Type 80 globe? They have worked well for many, but not lasted well for everyone...
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Dana
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Re: NOS tube questions
Reply #17 - 10/07/21 at 20:50:49
 
No I experienced this with the original tube provided by Decware.  I purchased a couple of NOS 5z3s for cheap and the 4 to 8 pin adapter that I want to try and I'm trying to see if there are any steps I could take that would extend their life expectancy before I finally invest the BIG bucks into a high end rectifier. My other option would be to  purchase a VARIAC.

What I'm taking from the discussion is arcing is bad and may be the forerunner to tube death is that correct?


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'Cause the piano has been drinking,
The piano has been drinking
The piano has been drinking,
Not me, not me, not me, not me, not me
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will
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Re: NOS tube questions
Reply #18 - 10/07/21 at 22:19:10
 
I think so... that arcing is an indication of problems. But as I said, sparking when hot is not necessarily deathly in the short run, at least here.... sometimes yes, and sometimes no. Presumably it will at least shorten tube life in some way though. Was that stock tube a Valve Art or Shuguang 274B? I had one of those spark on startup and last quite a while, though I did not use it as long as these 4 volt tubes.

Unless you are using tubes known to be borderline electronically, I think a lot of times it is just a defect in a tube, whether new or old, and I personally don't worry about things like a variac when using tubes that act right. I used 5U4G-ST types for many years, very close to 5Z3s, and they lasted and lasted for the most part... well made, and the electronic specs right for these amps.  But on rare occasion, I got some old tube that was compromised and failed.... So I would think that if your 5Z3s are not damaged/compromised, they would probably last a really long time with normal use.

It does seem a variac could help with lengthening the life of rectifiers.... especially with suspect tubes, but I wonder how much it would downgrade the sound quality of a high end tube. Would the trade-off be worth it, the variac effecting the sound of every part in the amp. I have one and tried it to force my house voltage down into a range where I preferred the sound. It could be 123 volts out of the wall, and I prefer my system sound at 117-118 volts. This made a big difference in sound. The higher the input voltage with my Toriis, the denser/darker/thicker the sound... not where I was wanting to be. But I could hear masking/veil degradation from the variac none-the-less. And this makes sense to me because they are made for variable voltage control, not audio. And we know that different receptacles, switches, resistors, wire metal purity and forming methods, etc, all influence the sound via the quality of the energy power supplies produce... whether in amps, power filters, regenerators, audio system receptacles, house wiring, you name it. With transparent and resolving systems we can hear these things individually, and they can really add up, often appearing to be OK until we make them collectively better and then, Wow!

I ended up finding a demo PS Audio P5 regenerator. And it has a sound too, but after some modifications and a special power cord I like it for the most part...not totally transparent and fast, but getting there. And I am glad to be able to tune for steady, regulated voltage and phase specifically for my house power, system, and tastes. All make a notable difference here.
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CAJames
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Re: NOS tube questions
Reply #19 - 10/08/21 at 02:30:16
 
What I'm taking from the discussion is arcing is bad and may be the forerunner to tube death is that correct?

I'm going to say categorically yes. If a tube arcs there is a problem, and it is almost certainly the tube. There is a (very) small chance there is a problem with the amp itself but IMO you should absolutely try a different rectifier. If there is no arc then the old rectifier was bad: throw it out and move on. There is no reason you should need VARAIC, although it only makes things better, at least for tube life. I'll defer to Will on how it may impact the sound. FWIW below is post by Steve regarding rectifiers that lines up perfectly with my thoughts on the subject as well.

Quote:
Re: Roll Rachael Roll
Reply #13 - 06/23/20 at 06:08:32
Some great feedback regarding quality tubes...  

The beauty of a tube amp is that you can change the tubes.  You can change the tubes when they grow tired and lazy sounding over time... or you can change the tubes when you grow bored or just want to take a different seat in the music hall so that you can hear the music from a different perspective. So this leads to tube rolling which leads to brands and types... and here is some of what I know that you should know:


Current production vs. New Old Stock. In my experience the only consistently solid tubes on the market today come from Russia. Brands like Mullard, Tungsol, Electro Harmonix, Sovtek, Svetlana. The rights to these brand names have been acquired over the years by New Sensor Corp in the USA, who is predominately a tube supplier for the music industry / guitar amps. They own or partially own factories in Russia.

Decware purchases it's Russian tubes direct from Russia in bulk with the exception of the larger output tubes (EL34/KT66/KT88) which are current production branded tubes imported into the USA. All of the the Russian tubes that we purchase direct from Russia are N.O.S. Russian Military Grade tubes. Many of them have Gold grids, thick glass, high G ratings for missile use, and longer life, in some cases 10,000 hours.  These are ultra-hi-end tubes in disguise and have always been.   To hear how good these tubes are you have to install an American New Old Stock rectifier tube.

My experience with Boutique Chinese brands is mixed. The sound is good, the reliability and or consistency is ridiculous. I have been purchasing samples of these fancy tubes as they come out over the past many years and I have an entire collection of crippled tubes. Even KT88's that cost $1600 a quad drifted out of usable tolerance within days and had to be replaced.

New Old Stock is the real deal. Those who like to push the envelope of what is possible with their amplifier will often go down this path with no regrets. For one thing, the tubes not only sound better, but often last longer, in some cases like with rectifier tubes up to 10 times longer.

Rectifiers are a subject all in their own. Russian rectifiers are acceptable, everything else is a no-go from a reliability standpoint with some rare exceptions that are very pricey. My advise to all Decware amplifier owners is to find yourself a New Old Stock 5U4 or a 5R4 that has never been used and comes in it's original un-molested box. Consider the current production rectifier tube we ship with the amp the best sounding and most attractive  option that will last long enough for you to find a real N.O.S. replacement.

Finding N.O.S. tubes is easy, even on eBay there are millions. Since you only need one or two you will have more to choose from than you know what to do with.  Finding quantity of these tubes is another story. If Decware could secure reliable inventory of 1000's of N.O.S. rectifiers, it is an investment we would gladly make but in 25 years is has yet to happen. Because we can't find N.O.S. tubes in large quantities, even batches of 100 would be gone in less than 30 days, we feel there is no point in even trying.  

For the customer it is easy, just find a N.O.S. 5U4 tube on eBay that is unused, and in it's original box for $40 and it could easily last for 10 years or more and sound better the entire time.

As an amplifier designer, it is possible to create circuits that baby the rectifier tube by limiting inrush current, using smaller capacitors, running higher voltages with a choke and so on.  Correctly done, this can make a Chinese rectifier tube last the full rated 500 hours or more.  The problem with this is that it changes the sound quality of the amplifier well outside what we find acceptable.  So, we have to make a choice, do we design tube amplifiers to baby the crappie rectifier tubes being made today, or do we design amplifiers to use REAL tubes.  Of course the answer has to be REAL tubes, because we make real amps.
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Dominick
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Re: NOS tube questions
Reply #20 - 10/08/21 at 08:24:37
 
A while back before I had placed my order for my Torii… I was doing some research on rectifiers.  I went Down a small rabbit hole and was inquiring about the EML 5U4G mesh plate rectifier.

http://www.emissionlabs.com/datasheets/EML5U4G.html

When I looked at it further I realized that it may be a borderline rectifier to use due to the specs.  The first capacitor required was 40uf and it’s a 5 volt tube.  While I forget whom I had the conversation with at the time… It was recommended that if I wanted to try that rectifier that a Variac could be used for a soft start up.  At the end of the day I decided it was not worth going any further and jumped out of the rabbit hole and moved on.  

Out of curiosity… Has anybody used this rectifier in their amp with success?  I’m asking because I never really got any closure on whether or not the specs and requirements on this rectifier would cause potential damage to the amplifier if used.  

Dom

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CAJames
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Re: NOS tube questions
Reply #21 - 10/08/21 at 15:20:39
 
I can't speak directly about the EML 5U4G (although a lot of people I know really like it). But I will say there is a fair amount of confusion, or ambiguity, about rectifiers and the recommended first power supply capacitor.

I guess it really boils down to this, my understanding is Decware amps have a first power supply cap that is 47 uF, which just happens to be the spec for the 5U4/5Z3 rectifiers. And in theory any rectifier that is spec'd for less is "dangerous" because the initial current inrush when you turn on the amp can damage the rectifier. But Decware sells, and recommends, the 5Y3 rectifier, and I've seen datasheet values ranging from 15 uF to 33 uF for that tube. Steve also recommends the 5R4 rectifier, and according my RCA tube handbook the first power supply cap ought to be 4 uF for that tube. So there's that.

I'm not going to tell anyone that the first power supply cap spec doesn't matter, but IMO it seems more like a guideline than a rule. For me, I feel like the currents generated in my UFO amps are small and the quality of NOS rectifiers are generally so high that I'm not going worry about it. If you have a higher powered amp the situation may very well be different, so all bets are off. The other thing is, and while I'll never say never, it is highly unlikely that using a rectifier that is spec'd for too small a cap will damage the amp. The "damage" is the rectifier tube ages more quickly and will fail sooner. Usually it will start to arc and pop before it fails but in general the worst case is you blow a fuse, just like if a properly spec'd rectifier reaches the end of it's life.


I'll also mention some rectifiers, and I'm specifically thinking of the GZ32/5V4 and GZ34/5AR4 although there are others, are  "indirectly heated" tubes, which means they power up slowly over several seconds as opposed to almost instantly  for your 5[U|R]4s and 5[Z|Y]3s. How they actually sound is a totally different question, but if you're concerned about tube life get an indirectly heated rectifier and your tubes will benefit from a soft start without having to mess with a VARIAC.
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Re: NOS tube questions
Reply #22 - 10/08/21 at 20:35:03
 
Dominick,

I have been running the EML 5U4G mesh plate in my SE84UFO25 since March of 2019 without issue.
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Re: NOS tube questions
Reply #23 - 10/11/21 at 01:33:06
 
I can add my experience here as well. Mostly due to ignorance regarding any engineering numbers I should be looking at, I have run EML 5u4g and 274b mesh plate tubes, all the PSVane recitifers, Takatsuki 274b, various metal/plastic base Mullard/Amperex GZ34, metal 5AR4, RCA 5R4GY, and WE422a. My Taboo and CSP2+ have run everything without issue.

For input tubes, I've run 6922 without adapter, 12AU7 without adapter, 6SN7 with adapter, 6F8G with adapter, dual 6J5 with adapter.

Thanks,
Richard
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Re: NOS tube questions
Reply #24 - 10/12/21 at 06:06:18
 
CAJames, MrDerrick, and morph…. Thank you for your input and it’s good to know that you have been running that rectifier without issues.  

CAJames…. Yes you are correct that there is a bit of confusion and ambiguity around the first power capacitor in relation to rectifiers.   I’m guessing that with the lower powered Zen amps..it’s not as much of an issue as with the higher powered amplifiers.  If the potential damage was only isolated to the rectifier being used… then that’s not the end of the world. I would be more concerned with causing internal issues with the circuitry of amplifier itself.  

Dom
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Re: NOS tube questions
Reply #25 - 10/12/21 at 09:59:04
 
Dom,

Have you received your Torii yet?
If you are still waiting, will it be a "MKV" version?

From the Torii product page;

"This new model features for the first time an 8uf input capacitance on each rectifier for a softer startup to increase tube life."

If the 8uf is the first cap, you could probably run just about any 5 volt octal rectifier without worry.

The EML 5U4G mesh plate is a very large rectifier, check your clearances!
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Re: NOS tube questions
Reply #26 - 10/13/21 at 06:04:55
 
MrDerrick,

I have had my Torii MKIV 25th for like 6 months now. Steve did the design change like 2 months after I took delivery.  

I feel the amp is fairly broken in by now that I am going to start tube rolling. I have a really good feel for the sound of this amp, so the rectifiers are the first choice.    I have only tube rolled my ZSTAGE with the Torii thus far with nice results.

Dom


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Re: NOS tube questions
Reply #27 - 10/13/21 at 14:56:57
 
Dom,

If you are still considering the EML, ArtAudio US was the best price including shipping that I have found. I would like to know if you find a better price.

I actually have a spare that should arrive this week.
I'll test the new along with the 2+ year old and see how they compare.

There's well over 5000 hours and maybe even closer to 10,000 hours on the 2+ year old rectifier. Every week I'm powered up for around 3-4 days at a time.

EML has detailed burn in instructions for the 5U4G mesh.
I can't recall the exact hour cycles for burn in, but I followed them.
I'll see what instructions are with the new tube.

BTW, the EML sounded very good straight from the box, I had an Aqua that I was running in at the time and I never put it back in after the EML was in place. I really should have given the Aqua time to settle in, but the EML was so much better from the start.

I did register the rectifier for the 5 year extended warranty that they offer, though It probably would not be valid with the first cap sizing of my amp.

What I would like to know from any other Decware amp user, have you replaced the internal rectifier fusing with upgraded fuses?

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Re: NOS tube questions
Reply #28 - 10/13/21 at 15:36:14
 
MrDerrick wrote on 10/13/21 at 14:56:57:
What I would like to know from any other Decware amp user, have you replaced the internal rectifier fusing with upgraded fuses?


A good question. I haven't seen anyone catalog any impressions or experience.
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Re: NOS tube questions
Reply #29 - 10/15/21 at 00:51:13
 
It appeared that the Valve Art 274B that came stock with the amp was having a plate coating issue and when it started first time today  little burning embers would shed off the bottom.  It still worked but it is now relegated to the back of drawer.
It also was a just a 4 pin tube but had the key race so it could only be put in one way. The 5z3 is a 4 pin with no key race so I used the adapter.  The cheap adapter had no markings on the top and it was hard to tell which holes took the big pins and which holes to smaller ones.  The 5Z3 tube only seemed to go in one way but saying I was a little anxious when I turned the amp on is an understatement.
The good news is it worked and sounded much better right of the bat.  Its got a couple hours on it now and the sound is smoother, deeper and to me  the most noticeable is guitars seem to jump out at you and vocals have lost the glaring texture I was noticing with the Valve Art rectifier tube.  I bought two rectifiers for 6.95 plus shipping and haven't tried the other one yet.  
Man this is fun and I'm just grinning listening.
Thank you Steve for a great amp and Thanks to everybody else who was willing to share your experiences.  Hopefully I'll be able to pay it forward to someone in the future.
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Re: NOS tube questions
Reply #30 - 10/15/21 at 01:09:28
 
Great news Dana! Now you may be in trouble, "needing" to explore tubes more, and more, and more, and more. In an advanced form of the malady, you could end up like me...not having counted, but guessing I must have somewhere between a hundred and two hundred NOS tubes around!

Roll Eyes

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Re: NOS tube questions
Reply #31 - 10/15/21 at 01:40:28
 
First comes the Decware family, then the tube rolling obsession. Enjoy the journey, and keep us posted on your adventures.

Glad the 5Z3 worked out for you. Honestly I never even put the stock rectifiers in my amps, I just went straight to NOS. As Steve says in the post I quoted earlier, the stock rectifier is just there to hold you over until you can get something better.

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