最近陸續售出一些USAF-596,有同好問我USAF-596的聲音表現,發現網路的訊息太多了,剛好有國外有一位同好比較過各種5U4類似的整流管,在這裡翻譯給大家參考,另外我也用ChatGPT幫我整理一下,USAF-596全世界的評價,這些評價當年USAF-596價格還不算高,但隨著越來越多人認為USAF-596應該是舉世最佳的整流管,或是整流管中的殺手等,USAF-596就開始被很多人收集,價格也越來越高,目前單顆價格已接近台幣15000元,雖然沒有WE274B那麼離譜過也是很驚人了.文中當年USAF-596的網路價格僅100-200USD,已經被稱為極為昂貴了.

(一)ChatGPT幫我整理一下,USAF-596的評價

(一)各種5U4類似的整流管的比較(順序與聲音表現無關)

------- ChatGPT 翻譯成中文

8. United Electronics (USAF) 596

目前市場價格每支約在 $100 至 $200 美元之間，視管況與賣家而定。但我認為它完全值得入手，這是我最愛的整流管之一！

Anyways here it is! And in no particular order...


1. Western Electric 422A (early 50's grey plate and later 60s black plate)

This is Western Electric's version of the 5U4G, with slightly different specifications, it should be fully compatible with 5U4G amps (Stratus - maybe, Woo, Decware, etc.). The construction is quite interesting, having the same domino plates and overall build as the Tung Sol 5998 power tubes. Anyways, the sound? This is by far the best tube I have ever owned or heard. My reference tube. As with many of the rare holy grail super tubes out there, they are nearly perfect in every way. Hauntingly beautiful tone, lots of air, great layering, transparency above the rest, and just perfect extension in both the highs and lows, deep bass, palpable, lucid midrange, holographic 3D staging and imaging (like with the WA22 and Glenn OTL, the image is very life-like and out of head unreal good at times), amazing! Overall balance is great as its neither overly warm nor bright, transients and PRaT are as good as they get with tubes (like seriously, beautiful liquid transients!). Out of both tubes I have, I think they both sound pretty much identical, the older grey plate looks a little nicer and might sound a bit better, but they're pretty much the same tube. Price is generally high with singles being anywhere from $400 to 750$.

2. GEC U52/5U4G/CV575 (Brown base)

British tube made by GEC/MWT/Marconi/Osram, etc. I've also seen it branded under Mullard or Brimar. It should be compatible with most 5U4G amps (I have confirmed compatible with Woo WA22 and Stratus). Mine has grey plates but I've also seen black plates as well as black base versions of this tube. Compared to the Western Electric 422A, I think this would be the second best rectifier tube available. Performance is almost the same as the Western Electric 422A, perhaps only being a little warmer and having a more euphonic tone/timbre/decay. However, it maintains its speed, transparency, layering, soundstage, and imaging. Like the WE422A, it's pretty much nearly perfect in every way and maintains a sort of neutrality throughout. Warm tube sound but with extended air and treble, great staging, deep bass extension, very nice texture and decay as well. Absolutely zero grain with this tube, just like the WE422A, one of the best tubes out there! Sound-wise, it's very similar and shares the same British tone and sound signature of the GEC 6AS7G power tubes. Great synergy with Sennheiser HD 800. Just like the WE422A, this tube can really bring you to tears on the right music, so much magic in the sound of legendary tubes. Price is slightly cheaper than the 422A but similarly priced with tubes going for $350-500$ a piece.
　

3. Mullard/Cossor CV378/GZ37/53KU (fat bottle GZ37) (Brown base)

Another British tube, this one made in High Wycombe, England around the early 1950s. I've seen it branded as Cossor, Mullard, and GEC/Osram/Marconi/etc. It comes in brown or black base as well. This is a very nice tube overall. Its slightly warmer than the GEC U52, offering a little more bass body and punch and more warmth while maintaining good speed and PRaT. Transparency is very similar, offering liquid silky smooth transients and a grain-free presentation. However, this tube is warmer, not as airy, and the slight extra fullness and more tubey midrange make it a little slower overall. For brighter setups and headphones, this tube offers top-level performance while maintaining clarity and detail. It doesn't veil the midrange or treble like cheaper tubes would (this is very noticeable on headphones like the T1 or the HD 800). This tube is also great for jazz and vocals, very natural timbre and tube warmth. Great bass performance and warmth make this tube a winner for me. Unfortunately, this tube can be hard to find, often selling for $300-450$. It is cheaper than the U52 or WE422A though and might be good for those wanting to use it in a WA5 or WA6-SE. Compared to the newer and much more commonly available Mullard GZ37/CV378 skinny bottle, this tube is much better since it's not as slow and the bass is better textured and cleaner sounding as well as being faster and more resolving overall.


4. Mullard GZ34/5AR4 (metal base)

Metal base 5AR4 made by Mullard/Philips (Miniwatt) /Amperex (Bugle Boy logo) in the 1950s before it got replaced by the black base version which is much more common and not as good sounding. This ranks amongst the best tubes I own and I would place it in the top tier with the WE422A, U52, Cossor GZ37. What I really like about this tube is the cool tonality it has while maintaining tube euphony and inherent warmth. Along with this coolness (think of a minty cool kind-of sound), it has a very liquid-like decay and grain free presentation. Transparent, great clarity and treble extension. The midrange is quite neutral as well, having a nice slightly forward presentation while maintaining a good soundstage and image. Timbre remains natural as well as the decay. This tube is very dynamic as well, having some of the best dynamics of any tube. Want to make your amp more neutral and more SS like, while maintaining tube goodness? This is the tube for you! Bass is also amazing having a clean decay, good texture, and deep extension. A nice mid-bass punch as well adds to the fun-factor this tube has. Great for rock, pop, and just about any music in general. Got a slightly sluggish amp or using warmer headphones like planars or Sennheiser HD 650? This is the tube for you! Liquid, liquid, liquid minty coolness, that's about the best way I can describe this tube. Unfortunately, this tube is getting quite rare and hard to find. It often sells for around $350-$500 NOS and sometimes up to $700-$800 for NIB! The Western Electric 422A might be a better buy at those prices. Anyways, this tube is definitely worth trying out! Also to note, this tube is supposed to have a huge lifespan, many lasting for over 40 years in use and anywhere from 10,000 to 30,000, and even 100,000 hours! Now I'm not sure how long exactly they will last, but these just about last forever!


5. Mullard CV378/GZ37/53KU (skinny bottle GZ37) (Brown base)

This is the newer version of the GZ37, made in the late 50s and 60s. It was made in Blackburn, England rather than High Wycombe like the older fat bottle version. Sounds like the fat bottle GZ37 but with a few differences. Soundstage and image remains good, very wide and with great depth. But it lacks some of the fine layering of the older version. Transparency is almost as good, offering a somewhat grain-free presentation, but perhaps not as liquid smooth in the decay and transients. Treble isn't as extended, though warmth remains the same, this is a warm and laid-back tube. Bass is nice and full with good body, but it does lack the extension of the older version, by just a bit. It's also slightly less textured and has a little more overhang and it's not as refined overall. Dynamics aren't as good either. Details and nuances don't come in as cleanly as with the other tube, its more smoothed out and it seems like it can't resolve quite the same. The midrange seems a little darker as well. Overall, this is a good tube for those wanting a warm and laid-back presentation. For the price, this is a pretty good tube, but it definitely doesn't compare to the older GZ37. This tube tends to sell anywhere from $80 to $150 per tube.


6. Mullard GZ34/5AR4/CV1377 (black base)

Black base 5AR4 made by Mullard in the Blackburn, England factory. This one is from the 1960s and was branded as General Electric. I've seen all sorts of brands for this tube, but they should all be made by Mullard as long as the etched code, construction, and branding are appropriate (there's straight plates as well as later 4 notch and 7 notch versions out there). This is the regular 4 notch black base GZ34, there is also an earlier fat black base version that came shortly after the metal base was discontinued, it generally costs a little more than the regular black base but not as much as the metal base. There is also a brown base version of this tube, which might be more closely related to the metal base version, and is labeled as CV1377. This tube maintains the same general sound signature of the metal base, but with differences. The minty cool sound is there, but perhaps this tube is slightly colder and more Solid-State like. The decay remains fast and clean, but lacks the liquidity of the metal base, the clarity is pretty much the same, but the transparency isn't as good. There is a tiny bit of grain at times with this tube. The treble is just as extended but has a little more hardness than the metal base. The soundstage/imaging is more narrow, dynamics are similar but there is more of an aggressive forward nature to this tube. The midrange unfortunately seems a little leaner to me on this tube and the bass while punchy, becomes not as extended and lacks some texture. Detail is good on this tube but not quite at the level of the metal base, I find it harder to hear some things and it lacks the layering and depth of the metal base as well. Overall, this tube is nice for those wanting a more neutral and faster more solid-state presentation, however, it lacks some of the refinements of the metal base. While the metal base GZ34 is amongst the best tubes I've heard, the black base is simply good but not amazing. This tube generally sells for $70-$130 a tube (and like $150-200 for the fat black base version and the brown base version) which is a pretty good deal for those looking for a long lasting rectifier, this tube has the same lifespan and longevity that the metal base is known for. It is also much easier to find and there are plenty for sale online. It just isn't as perfect or refined as the metal base unfortunately.


7. Emission Labs (EML) 5U4G mesh plate (newer ceramic base version)

This is a new and current production tube made in the Czech Republic, and is very popular amongst Woo Audio amp owners. Sound-wise, I find this tube to be warm and full sounding offering good bass punch and body as well as a nice sweet midrange. It's a well balanced tube that maintains coherency and extension in the bass and treble. The treble is quite warm and forgiving, yet has enough extension and detail to avoid veiling, it is on the warmer side though. The midrange is slightly pushed back due to the lushness, but remains good overall. The bass is punchy and has good extension, though the sub-bass might be a little lean at times. Decay and speed are good, above average, but don't exactly reach the levels that the rarer U52/W422A tubes do as there isn't that magic liquidity and grain-free clarity; though it comes very close. Tonality isn't as good as the best of the best, but is pretty nice overall. Detail is overall good, being able to pick out nuances in certain tracks and not in others. Transparency is good, but there is a slight veil at times due to the warmth, though it is slight. The soundstage and imaging is great, having a decent width and great depth, a very 3D sounding tube at times, layering isn't as good as some of the better tubes though. Overall, a winner, surprisingly good for a new production tube, and above average to most tubes. The price is a little on the high side, since this tube is around $250. There is also a solid plate version available, but I have not heard it. Beautiful looking tube and larger than most tubes, but the tube might not be as durable as the older tubes being more sensitive and "wimpy" in a way. The tube does darken quickly and lifespan might not be as long as with NOS tubes depending on how hard your amp drives this tube. This has to be taken into consideration since there are plenty of NOS tubes available for less.


8. United Electronics (USAF) 596

Made by United Electronics for the US Air Force, with 2 of the pins being place on top of the tube to avoid arcing. It's supposed to be a high voltage, high altitude, military rectifier. Known now as the "Mighty" 596, this tube is similar to a 5U4G or 5U4GB and should work in most amps made for them. It is also similar to the RK60/1641 tube which is also a 5U4G. In my opinion, this is one of the better tubes out there and I would definitely consider it to be another of my reference tubes. Soundstage and imaging are very good, though the layering and depth are only average, well balanced overall though. Transients, PRaT, and speed are very good, not super liquid like WE422A or U52, but not too far off either. This tube never sounds congested and the decay is fast and clean. Transparency is very good and there is almost no grain in the sound. Timbre and tone are slightly warm to neutral depending on the amp. Treble is quite extended yet smooth and clean. On my WA6-SE this tube was more neutral and almost solid-state sounding, perhaps due to the general sound signature of the amp. On my WA22, it was slightly warmer sounding and smoother. On the Glenn OTL amp, it is slightly warmer as well. The midrange is nice and warm yet maintains a rather neutral sound overall, very clean. The bass is clean, well textured, and with some of the best extension of any tube. Very nice bass I think, it can be a little light at times, but that isn't necessarily a bad thing since the bass is so good. Overall, this tube is neutral to slightly warm but maintains good balance and is a solid performer at any level. It's hard to find flaws in the sound. Dynamic, detailed, accurate, and extended are words that would best describe this tube. Unfortunately, this tube is getting very rare. It is sold out in almost every store and very few sales pop up on eBay, usually with bids rising quickly and selling quickly. Price and demand are rising quickly with supply being harder to find. This tube sells anywhere from $100 to $200 per tube depending on the seller and condition of the tube, but I think it's worth it! One of my all-time favorite tubes!
　

9. Raytheon RK60/1641

Made by Raytheon (and also General Electronics as well as a few others), this tube is similar to the 596 and the 5U4G/5U4GB. Construction is similar but instead of little pins sticking out, its buttons. Like the 596, this tube is a very solid performer and it really doesn't do anything wrong. Bass extension is slightly less but similar. Treble is smooth, clean, and extended at the same time. The midrange is slightly warmer than the 596 but remains somewhat the same. Soundstage and imaging are above average and while not amazing and holographic, are decent. Tone and timbre are nice and tubey with a euphonic warmth. Clarity and detail are good as well as transparency. There is a little bit of grain at times since the decay isn't as liquid or clean as with the more expensive tubes, but there isn't any hardness or grit as you would find with lesser tubes of this price. Resolution is above average but not the best. Bass texture could be slightly better as well as midrange detail, the warmth kind of takes away from it. This tube isn't overly lush like the GZ37 or even the EML, but its more than the 596. A nice tube overall especially for the price. This tube is getting rarer but prices are still under $40 per tube (sometimes even 10-15$ per tube!) and it is easier to find than the 596. A great bargain tube and certainly better than most! Comes close to 596 performance and some might even prefer this tube over it.

　

10. Brimar 5R4GY/CV717

Similar to 5U4G but slightly different, this one is made by Brimar. This tube is similar in many ways to the GZ37 tubes in that its quite warm. On the WA6-SE, this was almost too much, extremely syrupy and tubey midrange, very laid-back and lush. It did however, work well with bright headphones due to the treble roll-off. If you enjoy a warm and euphonic presentation, this tube is really nice. Compared to the GZ37's, I think it stands between the Cossor GZ37 and the Mullard GZ37. It's much better than the skinny bottle GZ37 offering more transparency (zero grain!) and a richer tonality, as well as better soundstage and imaging (rivaling that of the best tubes in depth and dimensionality). Bass is tighter and cleaner as well, though not as nice as the Cossor GZ37, its slightly less impactful and not as layered, but better than the regular GZ37 and with much better texture. While this tube lacks speed and PRaT, it does have a very natural decay and timbre, and is one of my favorite tubes for vocals and slower music. Overall, this tube is extremely good for the price, offering much of the performance of the more expensive tubes, having similar transparency and richness in tone. What's even better is the fact that this tube is still easily obtained and fairly cheap with prices ranging from $45-$100. Personally, this is a steal since I think this tube is better than the regular Mullard GZ37 and rivals the more expensive and rarer tubes out there. It is a little too slow for my taste, but if vocals, jazz, and classical are a large part of your collection, this tube is definitely a must have!
　

11. Philips 5R4GYS

Described by Upscale Audio as the "best 5U4G we've ever had", they have brought much attention to this tube, recommending it over many of the other rectifiers they sell. Compared to the Brimar 5R4GY, I believe this tube is slightly inferior, but might be preferred over it in some cases. The sound is similar, offering euphonic warmth and a sweet tubey midrange. However, its slightly airier and offers better treble. Unfortunately, this also adds some hardness that takes a while to disappear (this tube was grainy until about 100 hours of burn-in). At the end, you get a warm sounding tube that's similar to the Brimar, but being a little more dynamic and a little faster, yet similar in sound. It's a little more balanced overall, the soundstage isn't as deep but imaging is very good. This tube offers better PRaT and speed over the Brimar, which helps it become a better all-rounder. Tone, timbre, and texture is similar to the Brimar but perhaps not as rich. Bass is almost the same, offering a tight, deep, full presentation without being bloaty or boomy. Transparency and clarity are similar but in some ways, a tiny bit below the Brimar. Overall, this tube is pretty good for the price, and offers huge improvements over stock Chinese/Russian 5U4G's for only $50-60. It's a good alternative to more expensive tubes as well, but I wouldn't consider this tube to be anywhere near "the best".
　

12. RCA 5R4GY

A 1944 RCA 5R4GY with dark brown base and double getters, this tube is also available in a lighter brown base depending on the year (50s-60s), many of these were military made. Compared to the Brimar and Philips 5R4GY, this tube offers some similarities, but it's the most different sounding. It isn't as warm and tends to sound more neutral and has a more treble oriented sound overall. If you are familiar with the brighter tube sound of Eddie Current products like the Zana Deux, this tube has a similar sound overall. Very airy treble, a nice open midrange with a huge soundstage, and lighter bass. Tonality is colder than the other tubes but has some warmth, this tube has a slightly forward midrange that's open and very clear sounding. The soundstage is huge compared to the other two tubes, offering plenty of space with lots of air, the separation between instruments is very pronounced here, unfortunately layering isn't as good as the better tubes, lacking dimension and holography. The decay is more fast and not liquid smooth but liquid fast, offering an almost SS like presentation at times, but without the grain or edge. Bass is still tight and well controlled and defined, but offers a little less texture and a faster decay. Impact is also less and the bass notes seem to be spread out more and seem a little more distant. Detail and clarity is great but I feel that this tube lacks a little bit in timbre and tone. Transparency is similar to the Philips, being good but not great. Overall, I feel like this tube is a good performer for the price, it is priced similar to the Philips and can often be found much cheaper as there are plenty to go around. Personally though, this isn't one of my favorites, it can have a little too much treble emphasis at times.
　

13. RCA 5U4G

My RCA 5U4G appears to be one of the ones with smooth plates rather than the ribbed plates (the smooth plates generally seem to be more desired than the ribbed plate versions, not sure if there is any difference really). This is actually a very nice tube, I purchased this tube just out of curiosity (since Frank I has used it in his WA5 with good results), not really expecting a whole lot, but wow, this tube is awesome! It is very well balanced in every aspect, and has a warm tonality, but remains fairly neutral and just not bright or overly lush. Treble is beautifully extended, midrange is open, clean, and well presented, and the bass is tight and deep. This tube has very nice PRaT and is quite musical. Also, this tube is transparent, I hear no grain! Soundstage and imaging aren't quite as good as the more expensive tubes, but it isn't bad either. I'm surprised at how good this tube sounds, especially considering how cheap this tube can be obtained for ($15 to no more than $50), this tube is actually quite good and I think it's better than almost every current production tube available as well as most of the cheaper 5U4G's.

　

14. Sylvania 5U4G

One of the cheaper 5U4G's available, it's also often packed as a stock tube when buying a new amp; I believe Woo Audio used to do this in the past before they started including the Shuguang 274B. Overall, this tube is pretty good, it sounds similar to the RCA 5U4G, however, it is slightly less detailed and doesn't seem to offer the same clarity or transparency. It is close though. The overall timbre and decay is fuller and the tube is warmer, but there is also a slight veil to the sound. The bass appears to have a little more bloom and to be slightly less extended. I think this is a good tube for the price and is coherent and well balanced but the RCA 5U4G is better.


15. Tung Sol 5U4GB

Another cheaply available tube. It's a fairly neutral tube with a slight warmth. Compared to the Sylvania 5U4G, its more neutral, but has similar performance. I feel like this tube has a slight harshness and leanness to it. Overall, the tube is well balanced, but it isn't very resolving or transparent compared to many of the other rectifiers available out there. Speed and decay are good but there tends to be a sort of SS like hardness in the sound. Personally I do not really like this tube and feel that the older 5U4G are more natural sounding. For the price though, it might be ok. It's easy to get and cheap as well.
　

16. Sylvania 3DG4

The rectifier used by 2359Glenn in his OTL amp. This tube has different specifications from the other rectifiers and probably won't work in most 5U4G applications (3 Volts as well as a different pin layout, as of now, only compatible with 2359Glenn amps and other DIY amps), but I shall list it here just for fun and reference for Glenn amp owners. Compared to the Tung Sol 5U4GB, I think this tube is slightly better. It's a similar sound, but warmer overall. Soundstage is pretty good as well as coherency and dynamics. However, I personally do not like this tube either, it appears to suffer from the same problems as the Tung Sol 5U4GB, sounding somewhat harsh and lacking ultimate resolving ability. The good thing is that this tube is very cheap and can be gotten for about $3.00, that's about as cheap as it gets. It does sound better than the 5U4GB and than most of the Chinese/Russian new production tubes.
　

17. Shuguang 274B

Current production Chinese tube that can be gotten for around $15. It also is the stock tube that Woo Audio supplies with new amps. It's a 274B, so it probably won't work in all 5U4G amplifiers and has different specifications. Pretty much, this is a terrible tube. The sound is grainy and harsh with a congested soundstage and a confused overall sound lacking in coherency. The sound isn't very detailed and there can be fatigue in the treble despite the muddy veiled midrange. I would never recommend this tube and only mention it here as a reference. It's a pretty bad tube and should only be used to burn-in the amp or to include when selling the amp for testing purposes.
　

18. Mullard GZ32/CV593/5V4

Similar to the other rectifiers, this is another Mullard made tube labeled as CV593 and having a brown base. I believe there is a black base version and several variations of this tube out there. Mine was purchased from Upscale Audio since they seem to have a good supply of them and easily available. As soon as I put this tube in, I was surprised at how good it sounded! Personally, this is near the top of the list amongst the other really good sounding tubes. Transparent, tight-bass, beautiful midrange with a sweet tone, euphonic warmth and tube sound without losing any detail or resolution, vocals are amazing! Great extension in all directions and a great soundstage and image with great depth. Decay and timbre are very natural and musicality is very good. Sound overall is similar to the U52 and the other British tubes; amazing! This tube only cost me around 60$ and is readily available online. If your amp is compatible with them, buy them, performs much better than the price suggests!
　

19. Sophia Electric Princess 274B mesh plate

This is a current production 274B rectifier offered by Woo Audio as an upgrade to the stock tube. As with the other 274B tubes, it might not be compatible with all 5U4G amps, though Woo Audio amps are all fully compatible with this tube. Though this plate is sold as a "mesh plate", it is not a true woven mesh plate like the Emission Labs tubes, but rather a stamped mesh. This tube is a rather warm sounding tube, though not overly so. Tone is fairly neutral and not overly rich or overly cold, but accurate. The treble is smooth yet extended and airy without being overdone. The midrange is slightly forward with good definition without becoming edgy or harsh. Bass is deep and full but might be slightly bloated for some. There is a slight bass boost and some might find the colorations a little distracting, taking away from some of the transparency and detail. However, it also adds musicality and makes the tube forgiving of poor recordings. Soundstage is very wide and imaging is quite good. This tube has good PRaT as well and is very musical. Overall, I think this is a great tube and while not the last word in refinement, is definitely a solid choice that I think many amp owners will enjoy. While I think for $150 you can get NOS tubes that sound better, this is still a good buy and good for those who want a modern tube that's readily available and that performs well. Do note though, reliability of this tube might not be as good as NOS tubes, though they do say that when used properly, it should provide anywhere from 5000 to 9000 hours of life.

　

20. Emission Labs (EML) 274B mesh plate (older plastic base version)

This is a new and current production tube made in the Czech Republic, and is another popular choice for 274B amp owners. Like the 5U4G, it is available in a solid plate version as well. This is a pretty nice tube and on the WA22, I preferred it to the Sophia 274B. It is warmer and has less bass, but the soundstage is amazing. Extremely wide, holographic, and 3D like with lots of air, very magical sound. Treble is smooth and midrange is warm yet not overly colored. Dynamics are slightly less than the Sophia 274B but this tube is much sweeter. Tone and decay are quite natural. Compared to the EML 5U4G, it offers a similar warmth and sound, but has more treble and less body, the sound is slightly faster and there is better separation. Detail and clarity are good but not amazing. I really enjoyed this tube with the Sennheiser HD 800 and Hifiman HE-500 headphones. Overall, I think this tube performs similarly to the EML 5U4G but with a different sound and is worth checking out. For the price of $250 though, it might not be the best value out there.
　

Well, that's about it for now since those are the only rectifiers I have left (except the Shuguang 274B which got sold).

Tubes to be added to this review at a later date
-Tung Sol 5U4G
-Any other tubes I am interested in trying out