Folks I am going to start this post and it will be a long one. It's been promised for a while and it is the result of months of good old rollin'. Pictures first and I am sure you will know where I am going with this.
Brimar 5R4GY, Double D Getter, sometime 1950s, England
Osram 5U4G (early milspec GEC U52 and arguably better), inverted cup, 1950s, England
Sylvania 274B, 1942, D Getter, Milspec
RCA 5Y3GT, double D Getter, 1952, black base
USAF-596,
US Air Force version etc
Gear used:
Decware Taboo MK3 (we all know this one) w. Amperex "Pinched Waist" 6922, Amperex EL84s or 6P15P-ER milspec
Ariand FV34-A (Single ended speakers amplifier), 2x12W, Psvane EL34
Woo Wee (electrostatic headphones converter)
Stax SR-009, Stax SR-007 MKI
Custom made 96dB Front Loaded Horn Speakers (Fostex Full range)
Music:
Stockfisch Reference Recordings (various genres: vocals, classical)
Infected Mushrooms
Pink Martini
Leonard Cohen
Katie Melua
Pink Martini
Introduction:
For several reasons the rectifiers have always been to me a fantastic and de-facto way to tweak the sound to my preference or system changes. Firstly these coincidently or not work with both my amplifiers (and soon to be 3) and also for this reason I found them a very worthwhile investement. It's an easy swap too. No need for gloves as there's a good base and a lot of the time there's only one. This is a comparison where I tried to be completely unbiased by the price. Some of the above are extremely rare and expensive, some less so and some are incredibly overlooked. But we all know everything is fair in audio.
Why these? I have a lot of rectifiers of this type and I feel the below represent the BEST of the best in my collection. They are all well burnt-in samples and sometimes I compared multiple samples of one. There are variations, but roughly within the same decade you'd probably be in the same ball park. The fact that I already selected these out of many different models, they are ALL already SO very good. This makes it sometimes super difficult to rate them, and obviously preferences play a signficant role. To try to hit an average I used two very different sounding amplifiers (Taboo MK3 - quite neutral, Ariand FV34A - classic tube sound), different coloration headphones, SR009s extremely neutral and the SR007 MKI warmer. The speakers are in between the headphones in tonal balance.
Bass Impact/Weight:
Sylvania 274b > GEC/Osram U52 > RCA 5Y3GT > USAF-596 > Brimar
Bass Control & Tightness:
USFA-596 > Brimar > RCA 5Y3GT = Sylvania > Osram
This was very difficult to assess because all of these are close. The bass quantity is plenty with all of them.
I don't like bass weak tubes, and none of these is that. Also none of them really have flabby bass either.
It is difficult to call a winner though. The bass driver control and added tightness can result in aparent reduced bass weight. This is why I wanted to separate the two sections. Overall when I wanted to choose one tube for the overall combination bass presence and quality it was either the RCA or Sylvania. If I want top control it is the USAF-596. All of them did a great job here.
Male vocals (Tonality, Texture, Extension):
Sylvania 274B (WOW. To die for.) > GEC/OSRAM U52 (WOW Reloaded) = RCA 5Y3GT (WOW Incredible) > Brimar (Still WOW) > USAF596 ("Only" Excellent)
All of these tubes are very special and excellent with mids. Was it not, any of them would have otherwise been excluded from this round-up. In this select company it is the Sylvania that comes first due to the most fantastic mids texture I have heard. I do not know how they were doing things back in 1942, but while retaining exceptional clarity the mids are smooth and with formidable texture and tone. This said it's almost unreal there is something better than the Osram (which is the milspec version of the famous GEC U52). This one is also extremely impresive. What I said regarding the Sylvania applies here as well.
Female vocals (Tonality, Texture, Extension)
Osram > Sylvania 274B > RCA = USAF-596 > Brimar
While I already had the ranking done from before, I wanted to try a few more songs and start from scratch last night. This time I started comparing the tubes in the reverse order of how I classed them with male vocals. The Brimar was very good but it turned out as the least impressive in this great company. It has excellent tonality, but the texture did the least for me. Again this is only compared to the others. Moving next to the USAF-596 - it was an immediate added sign of goose bumps on the test track: Pink Martini - Taya Tan. The texture and extension were both a step up. I long deliberated back and forth between the Sylvania and Osram with female vocals. They are exceptional and exceptionally close to each other, but a bit different: while Sylvania digs in deeper vocal detail with a bit better extension, I give a slight preference to Osram's texture and refinement.
Treble Air/Clarity:
Sylvania > USAF-596 > Osram > RCA > Brimar
Treble Attack/Quantity:
Sylvania > USAF-596 > Osram = RCA > USAF-596 > Brimar
None of these is a bright sharp sounding tube. Yet there a differences. The only one that I feel coming a bit short in the treble department is the Brimar
I really like the air and treble extension of the Sylvania and USAF-596. It makes these two tubes sound just a bit clearer than the others. However in the case of the USAF-596 there is something with the texture of the upper treble that does not sound as natural as the RCA, Sylvania or Osram.
When it comes to overall treble quality with super air, extension and tone, it's the Sylvania that takes the prize.
The Brimar was not going to win any prizes here. The treble has a slight rolloff, but not a deal breaker. Definetely nothing compared to some chinese production tubes.
Cold/Warm:
USAF-596 -> Sylvania -> Osram = RCA -> Brimar
Speed:
USAF-596 > Sylvania > RCA = Osram > Brimar
Clarity/transparency:
Sylvania 274b = USAF 596 > GEC/Osram U52 = RCA 5Y3GT > Brimar
Soundstage size:
Sylvania 274B > USAF-596 > GEC/OSRAM U52 > RCA GY3GT > Brimar
The USAF-596 produces a very wide spacios soundstage. The Sylvania while still very wide in presentation, has additional height and depth. These two are the rectifiers for large scale orchestras and classical musical.
The others are respectively more upfront with a gradually more intimate presentation that caters many modern genres and smaller ensembles even more.
Conclusion:
Best overall you're saying? Firstly the obvious caveat is: This is a tube out of many in a component (or two) part of your system. I obviously can't provide the right answer for something I do not know. Second of all, preferences are anyone's. I always look for synergy and good balance, as no system is perfect or perfectly balanced. This is a reason I favour having some tube gear, as it facilitates fine tuning through tube rolling. For my almost neutral sounding Taboo MK3 I had most of them for an extended period of time in combination with diverse output and input tubes, but a good 60% of time the RCA tube was running the show. For my warmer speaker amp I prefer the Sylvania, USAF or Osram.
I also want to add this should not be read by just looking as what came "first" and "last". These I repeat are what I consider my top 5 tubes. I personally think highly of each one of them.
Value:
Value wise if I only had a small budget to spend on a rectifier, it has got to be the RCA. It's a no brainer. I paid 30-40$ for each of mine, including shipping to far away.
Moving up the cost next is Brimar. Unless I find my system a bit too bright, I would actually probably stretch to the USAF-596. They go for 100-150$ if you can find one that is. But if you ask and look around there are still a few. The first was difficult for me to aquire and then I found two more NOS. They are not going anywhere, that's for sure.
The Osram was a very lucky find through a British army person. The base was loose and the guiding leg is missing. I don't have high hopes I will find another one for a non astronomical price, and yes it's a very special tube. The equivalent, the GEC U52, is avaible here and there, but expensive.
Now the Sylvania 274B is the oldest made and most expensive of them all ... it's everyone's decision whether it's worth it. But if you decide it's not or you cannot find one, worry not. The USAF-596 or RCA are in the same tier.
Notes: I also have more recent editions of some of these tubes. Moving into the 1960s and later... it wasn't quite the same quality with many times a drop in SQ.
