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Are you this R.Lawry? re: "listening notes"

I tried sending the listening notes to your other e-mail address but it bounced back, so I am trying the cut-and-paste method.

I now have a solid-state amp, which I would have previously regarded as heresy. I was beta-testing an amp for Michael Yee, who designs phono stages etc. for Musical Surroundings and others. It uses some new type of circuit and MOSFET, and blew me away the first time I heard it, so I bought it and sold the tube amp and tubes. I still have a CAT tubed preamp though. Hope this works.

Output Tubes

Chinese KT88: These tubes were the stock tubes in the AES AE-25 Superamp, probably because they were the cheapest good-sounding new production tubes, other than the JJ E34L IMO, whose supply Cary Audio can guarantee. I can see why Cary used the KT88 rather than the E34L because of its greater power output. And the first time I heard this amp I was blown away, as it definitely was the best-sounding one by a wide margin. However, compared to all other tubes I have tried, most notably the NOS ones, these tubes are found wanting somewhat. Are these Chinese KT88’s bad-sounding? No, not at all. But soundstage dimensionality, quickness and detail, warmth, dynamics, bandwidth is superior with the other tubes. The Chinese KT88 is full-sounding with a big soundstage and fair transparency, and punchy bass, but as with most new production tubes, lacking in dynamic range, detail and refinement, as well as bass clarity and extension. Bass is more full than with the various EL34’s and 6L6 variants, but doesn’t have that sock-in-the-gut extension that those tubes, at least the Amperex EL34, Mullard EL34, and Mullard EL37, have, making it difficult to distinguish bass guitar from bass drum. And it certainly is not in Philips 6550 and Sylvania 8417 territory. String bass is full and woody, however. Highs are sweet but rolled off and have more of a white noise character, but still aren’t bad. Details in voices and instruments are missing, as well as soundstage detail and depth. It is more difficult to pick out individual instruments and how they are played. If I had to use a word to character these tubes, it would be bleah. They are certainly not annoying, but nothing to get excited about.

Svetlana KT88: (Letter I sent to Kevin Deal of Upscale Audio): I tried the Svetlana KT88’s as replacement for the stock Chinese ones, and I totally agree with the results found by your friend Bill. As much as I found the EL84 current source tubes to make a difference, the improvement wrought by the Svetlanas was much more impressive. I even liked the looks of the Svetlanas, as they are considerably taller and clearer than the Chinese tubes. There was definitely greater soundstage transparency, detail, and a sense of envelopment, i.e. the feeling that you are sitting on the stage with the performers. Dimensionality is better than most tubes, including the Chinese KT88, and the soundstage is more open. Overall warmth is also greater, similar to the Tung-Sol black plate 6550, but falling a bit short of the GEC KT88, Visseaux 6L6G, or NU 350B. There was a lot more bass punch, extension, and definition, although these tubes are brighter than the KT66’s and 8417’s. It is tough to get increased detail without the brightness, and the Svetlanas fall into this category, although the brightness is not objectionable.

GEC KT66: Speaking of GEC, I tried the Genalex KT66, and again, Bill was right on. Although the bass depth was somewhat reduced from that using the Svetlana KT88’s, and was downright loose on some recordings, who cares? These totally transformed the Superamp, as there was a new clarity in all areas: soundstaging, highs, voices, instruments. Listening to Steely Dan’s Two Against Nature on vinyl, I couldn’t get enough. The music was mesmerizing and completely nonfatiguing. Bass was punchy, but lean, not terribly defined, and not extended on most recordings. On some bass-heavy recordings, like America Holiday, these tubes couldn’t quite keep up, causing a lot of boominess. Did I miss the deep bass of Amperex or Mullard EL34’s, Mullard EL37’s, Philips 6550, or Sylvania 8417’s? Well, sometimes, but not usually. The speed, detail, and transparency made me forget about the lack of bass on most records. Highs were very detailed and extended. The GEC KT66 has immediacy in spades. Using my Radio Shack sound pressure level meter, I was listening at only 94-95 dB peaks, which was much lower than the 100 dB peaks I need to listen to with previous tubed and solid state power amps I have owned. Yet I felt much more enjoyment listening to this amp with the KT66’s. I heard stuff on some of my recordings I have never heard before. These tubes have lots of detail and are quite transparent. Yes, they are not full and rich like KT88’s or 350B’s, but they are quick and detailed, and I certainly didn’t miss the extra power of the 6550 and EL34 family. If you can’t afford these tubes, it is time to get that second job at Domino’s.

Sylvania 8417: These tubes are physically smaller than most other output tubes, but were probably developed to give very high plate dissipation in a small package. Let me tell you that the 8417’s knocked my socks off. They didn’t have the relaxed ease of presentation of the GEC KT66’s, but had a similar level of transparency, soundstage envelopment, and clarity. The comparisons end there. The music using these tubes literally leaped from the speakers. I was taken aback with their dynamic range, bass extension and clarity, and detail. The bass isn’t as prominent as with the KT66’s, or even the KT88’s, but it is much tighter, extended, and defined. There seemed to be an extra half-octave of bass, which seemed to cause the room to move around me. These are the first tubes I have heard that have that bass growl heard on solid-state gear, as well as the bass extension and impact. I heard all kinds of new details on very familiar recordings, like how acoustic guitars are played, saxophone fingering, voices, etc. The nice thing about these tubes is that they had all of the above without sounding hard or brittle, and they don’t have the brightness of the Svetlana KT88. They have tons of gain. I REALLY recommend these tubes. The Quicksilver Audio website says that it was felt this tube, one of the last to be developed, does some things that other tubes don’t, and I agree. In terms of bass extension, gain, dynamics, and speed & detail, they are startlingly superior. Nothing else comes close. The closest tubes in these areas are the Philips ECG 6550, Mullard and Amperex EL34, and perhaps the GEC KT77. And other aspects such as transparency, clarity, soundstaging, and tube glow are good. They are not, however, slow and round, nor are they relaxed. I biased at 50mA per tube.

Tung-Sol 6550: I absolutely love this tube, which is the most sought-after black plate version. It is similar to the Svetlana and GEC KT88, and has similar transparency, soundstage, and highs as the GEC. They are perhaps a little leaner than the KT88’s, but images are tighter, as is the bass, and there is more detail. And did I mention that big, big, big soundstage with the tight images that the DJH AE-25 is so willing to share? Perhaps better dynamics than the KT88, but not the equal of the 8417’s, nor is bass depth or gain. Bass is extended and punchy with good definition. More forward than the GEC KT66, but have some of that ease of presentation. Voices are eerily real. And lots of that tube glow. The soundstage is transparent and detailed, and completely envelops the listener. I would say that the T-S 6550 and GEC KT88’s are champs in this area. IMO, the T-S Black Plate 6550 at prevailing prices are an absolute steal. They easily sound as good as any KT88 and prices are half that of the GEC KT88.

Ei KT90: Next up were these. And I must begin by saying that these tubes are a major pain in the neck. I put them in the amp, cooked them for several hours, biased at 50 mA, and started listening to a highly sought-after MFSL test pressing of Steve Winwood’s Arc of a Diver, but not for long. All of a sudden, there was a pop, and the music ceased. After my heartbeat calmed, I realized the tube fuse had blown, and a call to Kevin Deal of Upscale Audio revealed the need to cook the tubes for several days at a lower bias, and that their full potential wouldn’t be realized until the tubes had several hundred hours on them. At my current listening rate, this could be several years! Had I known this, I might not have bought these ridiculous things—what a joke! Well, after running them for several days, I was able to listen at normal levels, and so far, they are good-sounding, but nothing special. They have good dynamics and bass depth, but not in 8417 league. They are transparent, but not like KT66’s, KT88’s, 6550’s, or even 8417’s. Soundstaging is good but not exemplary. Their soundstage is flatter and smaller than that found with KT88’s, KT66’s, 6550’s, 350B’s, or even EL34’s and KT77’s, the last two not being the last word themselves in dimensionality. Clarity and detail are fine, but not in KT66, EL34, or EL37 land. Tonal balance is definitely lean, especially through the bass and midrange, and highs are extended but somewhat forward, which is probably exacerbated due to the lean sound. Either these things are highly overrated, they haven’t completely broken in yet, or I am biased (pun intended) because they caused me so much trouble in the beginning. Biasing them at 55 mA each as suggested on the Audioasylum website didn’t seem to improve matters much; if anything, they were even more lean.

Svetlana EL34: After my cherished experience with Ei KT90’s, I was relieved that the Svetlana EL34’s worked normally. I was surprised with these tubes in that I expected a creamy midrange with smooth dynamics and a slow, rich, traditional tube sound. What I experienced was a very dynamic sound with a full, deep bass. On a UK pressing of Genesis Nursery Cryme, I could feel waves of deep bass drum sound hit me. Again, the bass is not in 8417 land—what else is—but somewhat like KT88’s or KT90’s. They have a good soundstage, bigger than KT90’s, but don’t have as large a soundstage or that palpable glow and transparency of the 6550’s, KT88’s, or KT66’s. I was surprised at how incisive and upfront these tubes sound. They are somewhat less detailed and a little slower than other tubes, perhaps leaning toward fullness and opacity. I even tried old Mullard EL84’s and Amperex Bugle Boy 7189’s in place of the Ei EL84, but still, the Svetlana EL34 sounds a little small and hard. Vocals did have that palpable, alive, shimmering quality of better tubes, though. They do seem to open up and mellow with age, just like I did.

Sylvania 6CA7: After bidding on, and winning, a matched quad of Sylvania/Philips 6CA7 fat-bottle tubes on ebay, they arrived, with which I replaced the Svetlana EL34’s. This gave me a chance to compare the two. There was no comparison, really. I love these tubes, which, as stated on the Vacuum Tube Valley website, do sound different than EL34’s. And they should, as they are beam tetrodes, whereas the EL34’s are pentodes. Where the Svetlanas sounded small, bright, incisive, a little glaring and hard, and dynamic, the 6CA7 fat-bottles were much smoother and fuller, with a much larger soundstage, clean highs, and good dynamics. Soundstaging is good, although these tubes are not spacemeisters like KT88’s and Tung-Sol 6550’s. There is somewhat more detail than with those tubes, though. Compared to the JJ Electronics KT88’s, the soundstage is not as big or enveloping, but you can definitely hear more detail in the bass, how guitars are played, Fender Rhodes piano information, etc. And the tube glow I love in 6550’s, KT66’s, KT77’s, KT88’s, and 8417’s is in abundance here. They aren’t as relaxed as the GEC KT66’s or KT88’s, nor as detailed as 8417’s, but have a big, upfront, immediate sound, enveloping soundstage, and ease of presentation like the KT66. Bass is not as quick or deep as EL34’s, KT90’s, or 8417’s, but it is still good, much deeper and tighter than KT66’s, and quicker-sounding than that of the various KT88’s. Overall, these tubes sound similar to the Mullard EL37, although bass is not as punchy and dynamics are a little more restrained. And did I mention that big soundstage where you can point to the performers?

GEC KT88: After finding a good deal on these tubes from a dealer, I installed them with high hopes. And I wasn’t disappointed, although they didn’t have the clarity and detail of the GEC KT66. Bass was tight and punchy, though, like that of the Svetlana KT88, 6550, KT90, although, as usual, not in 8417 territory. These were richer in the midrange, but dynamics and deep bass was a little more reigned-in than the T-S Black Plate 6550. These probably have the biggest soundstage of all, and that fantastic tube glow and immediacy to boot. That shimmering, alive quality I love in tubes is found in copious quantities here. Saxophones and voices are vivid and up-front. Bass is full and weighty, giving the string bass a weighty, woody quality, perhaps a more real-life feeling than with any other tube. However, like the rest of the presentation, bass detail is easily trumped by other NOS tubes like the Tung-Sol and Philips ECG 6550, Amperex and Mullard EL34, GEC KT77, Sylvania 8417, or Tesla KT88. These last tubes have a lot more bass detail, dynamics, and extension. However, these tubes have a more lean, quick, and detailed presentation, trading this for much less fullness, dimensionality, and soundstage size. The GEC KT88’s were not as bright as the Svetlana KT88, and had a much more relaxed presentation—is this a GEC trait? And no other tube has the GEC KT88’s fullness, richness, bass weight, and soundstaging, not even the NU 350B, Mullard EL37, or JJ KT88. Good dynamics, perhaps a little less than that of Amperex and Mullard EL34’s and GEC KT77’s, which are second only to the 8417’s, and the highs were natural like that of GEC KT66’s and Tung-Sol 6550’s. One thing I was surprised about, though, was that they were quite revealing, and crappy recordings sounded so. But be prepared to bask in that warm tube glow. Overall, they are a winner, but are they worth the money? For my money, I would go with the Tung-Sol or Philips 6550, Sylvania 8417, or one of the better EL34 or 6L6 variants. IMO, the GEC KT88 is overrated and overpriced.

Amperex Bugle Boy Double-D Getter EL34: I bought a used quad of these from VTV, and on first listen, WOW! These are some great-sounding tubes. Maybe the best overall yet, although I haven’t listened to the Sylvania 8417’s since changing all the other tubes in the system. But, holy moly, these tubes have a rich midrange, sound quick and detailed, have great dynamics, clarity, transparency, big soundstage with tight images. Marti Jones’ Used Guitars sounded terrific—I was right there on the stage and the bass was tight and deep. If you like an upfront, immediate sound, these are the ones to get. The Amperexes are completely unlike the Svetlana version, which are quick and dynamic with good bass, but whose soundstage is small and midrange is hard and somewhat undetailed. And the Amperexes have lots of tube glow, but perhaps not as much as any of the KT88’s, the KT66, Sylvania 6CA7, or 6550. Nor are they as full-sounding in the bass and midrange as the KT88, EL37, 350B, 6CA7, or 6550 (although it does sound a lot like the Philips ECG 6550). But this tube is quicker, more incisive, and more dynamic with tighter images than the other tubes mentioned, as well as having more gain and treble energy. Definitely have to try those 8417’s again.

Mullard EL37: These tubes are listed by many, along with the GEC KT66 and Western Electric/National Union 350B, as the best 6L6 variant, although these are pentodes as opposed to the other beam tetrodes. My previous experience with pentodes such as EL34’s and EL84’s, is that they are forward-sounding, robust, and dynamic. Especially Mullard tubes. And the EL37’s were true to form, sounding more like an EL34 than a KT66. These tubes are definitely dynamic, with images pushed forward in the soundstage, robust, with punchy bass and clean highs, a lot like the NU 350B. As compared to the Amperex BB Double-D getter EL34, they have similar dynamics, but the bass is weightier and punchier, if a little less extended. The bass is completely different than that of the KT66, especially on bass-heavy recordings. They aren’t as detailed as the EL34’s, but are smoother, warmer, fuller, and have a bigger, but less transparent, soundstage. They have a harmonic richness in the midrange that is lovable, and are extremely revealing—I could easily hear differences when trying various 12AU7-type preamp tubes such as CIFTE 6189, Siemens 5814A, GE 6680, and Amperex 7316 PQ. They don’t have as much of that enveloping soundstage and tube glow as Tung-Sol 6550’s, Svetlana and GEC KT88’s, the GEC KT66, GEC KT77, but perhaps similar to that of the Sylvania 6CA7 and 8417.

National Union 350B: Well, folks, here they are, what I previously regarded as unobtanium. A quad of these showed up on ebay, a $550 bid was put up and then retracted, so I e-mailed the seller who sold me them for the same price. I love the looks of these, with the big ST bulb and high plates—very retro looking. The sound of these were as stated by others lucky enough to find them. Big, vivid, robust, full, with a healthy dose of clarity. They are definitely the champs in this area. Instruments were round and warm, and pushed forward in the soundstage like those of the KT88’s. Bass was full and electric bass purred, like the GEC KT88, although not as tight and extended as the 8417, EL37, EL34, KT77, or Philips 6550, but more prominent. Double bass was warm, big, and woody. Not as much bass definition or detail as an EL37 or EL34, but way tighter than a KT66. I couldn’t hear the slam of the bass drum as distinct from the electric bass as well as with the Amperex EL34 or Mullard EL37, but the bass was a lot more full and tuneful. Otherwise, these tubes had the clarity and transparency of the KT66, but warmth of an EL37, KT88, or 6CA7. Soundstage was perhaps not as large as the Tung-Sol 6550 or KT88, and didn’t have the pinpoint images of the 8417, but was definitely to die for, and much more warm and round than the 8417, as well as possessing that fantastic tube glow—that shimmering, alive quality missing in solid state equipment. Dynamically, they were the equal of anything except for the 8417, better EL34’s, or Philips 6550, and not as detailed as the 8417 or Amperex EL34, but more detail than the KT88. Since I just finished listening to the 8417, I had a chance to compare the two. I would characterize the 8417 as more intellectual, the 350B more romantic. The sound of this tube is as good as any I have tried.

GEC Gold Lion KT77: Another tube that I previously thought was unobtanium, I bought a black-base quad on ebay from a guy in Hong Kong. I don’t know how they compare to the earlier reddish brown base version, but they are not as stupid-expensive as those earlier tubes, which I have seen for $300-450 each. They seem to have some break-in time, as they continue to sound better and better. Even though they are beam tetrodes, they are considered part of the EL34 pentode family, and do have some family resemblance. The KT77 sounds like an EL34 but with a touch more warmth and smoothness, and a slightly bigger and more forward soundstage, like the Sylvania 6CA7. It has the greater speed and detail of the EL34, maybe a tad less than the Amperex Double-D getter version, but due to its greater warmth, perhaps the detail is there but not as apparent. Instruments sound more rounded and immediate than the EL34, but nothing like a 350B or KT88. And the tube glow of the M-O Valve Company is here as well, sounding like a KT66, KT88, or 6550. This is a terrific-sounding tube. Listening to a MFSL copy of Blind Faith, the guitars on Find My Way Back Home were right there, and the soundstage just wraps around you. They have good soundstage depth also, and did I mention dynamics—definitely as good as the EL34, KT88, 6550, and close to the 8417. Bass is extended and defined like the Philips 6550, EL34, EL37, and 8417. I like this tube a lot better than the GEC KT88. I can’t wait until these babies break in fully.

RCA 6L6G: I bought these tubes from Vintage Tube Services, which are the original 1940’s glass version of their 6L6. The plate voltage rating of these is 360 volts, and I am running at 495, so I biased at 30mA per tube, which Andy Bouwman at VTS and Kirk at Cary Audio said should be OK. To this point I have had no problems with the tubes, although their power output is definitely reduced. Unfortunately, right after I received these tubes I started having problems with the right channel, and after trying a multitude of fixes, including sending my cartridge back to Japan for repairs, I isolated the problem to my new Siemens-Halske CCa drivers in my amp. Now that I have listened to these tubes, I would characterize their sound as very GEC KT66-like, which is not all that surprising since the KT66 was designed as a 6L6 replacement without the “kink” in the 6L6 operating curve. Since I am not driving these tubes as hard as the guitar amp guys, perhaps this is why I can’t tell as much difference between the two. The 6L6G sounds very quick, open, and transparent with lots of detail like the KT66, and has a lot of the KT66’s ease of presentation, but the bass, while reduced in level and somewhat missing in action on certain recordings, is tighter and cleaner than that of the KT66. There is not the clarity found in the KT66, but I would consider these tubes a poor man’s KT66. Images are well-focused on the soundstage. This tube falls somewhat toward the lean, transparent, detailed end of the tube spectrum, certainly not warm and rich like a KT88, 6CA7 Fat Boy, or 350B. However, they are not as quick and detailed as the better EL34’s, Philips 6550. KT77, EL37, or 8417. Dynamics are better than I would have guessed, but are entirely eclipsed by the 8417, 6550, KT90, EL34, or KT77. I definitely like these tubes, but their lack of output power is probably their biggest drawback. Doesn’t seem to be too much of a problem for me, though.

JJ Electronics KT88: The first tubes I have bought in a number of months, I wanted to try them as the word on Audioasylum is that they sound a lot like GEC’s, perhaps more so than the Svetlanas. And I have to agree with that assessment. They are definitely full and rich, present not so much of a soundstage as a soundscape, have a sweet, but rolled-off, high end, and good, tight, extended bass. That alive, shimmering tube glow is here in spades, voices floating between the speakers, and instruments well-separated. They don’t seem as bright as the Svetlana KT88’s, but smoother like the GEC version, and dynamics are good, though probably not quite as good as the Tung-Sol 6550, GEC KT77 or Amperex Double-D getter EL34, and certainly not up to Sylvania 8417 standards. Quickness and detail, while not as good as the GEC KT66, 8417, EL34’s, or KT77, is still very good, perhaps the best of the KT88’s. These tubes, like most other new production tubes I have heard, have good warmth and soundstage, but do not have the speed and detail or dynamic range of the better NOS tubes, and have a tendency toward opacity. They do have better clarity than Svetlana EL34’s, but perhaps not quite as much as the Svetlana KT88 or Ei KT90. This is definitely a great-sounding tube, especially for a new production tube.

JJ Electronics E34L: These new production tubes have a really cool blue color, which looks great at night. They are also relatively inexpensive at $13.95 each. When I first put them in the amp I wasn’t too impressed with the sonics, as it was small and hard, but after a few hours, wow! These things are terrific! Much, much better than the Svetlana EL34. This tube has it all. Big, big soundstage with great dimensionality, tube glow, immediacy, good dynamics, speed and detail galore, good, tight extended bass, riveting (pun intended) highs. They sound like a good KT88, but with more detail and transparency, and better bass and dynamics. I was mesmerized while being immersed in the soundstage while listening to a Nautilus pressing of James Taylor Gorilla, and Holly Cole’s Temptation jumped out of the speakers and washed over me. The bass might have been a little too prominent, but it is partly the recording. Even with the speed fluctuations of the James Taylor (what is with the electric company and its voltage variations?!!) the sound was as good as a lot of NOS tubes. Maybe still a little short on resolution compared to the best NOS, such as the 8417, 6550, 350B, KT66, KT77, but in the same league. These things are definitely a well-kept secret, although VTV liked them. This is no doubt the best-sounding new production tube I have heard, rivaling even the Amperex Double-D Getter EL34 and the GEC KT77, and for the price, an absolute STEAL.

Philips ECG 6550: Bought these rare 6550’s from Kevin Deal of Upscale Audio, which have the word “aged” on the tubes, meaning they were burned in at the factory for military use, and Kevin also burned them in before testing. This means they should be well burned in, and their sound shouldn’t change appreciably with age. And some sound it is! These are great-sounding tubes—it seems like I like everything in this amp these days. Their sound is much closer to that of an Amperex Double-D Getter EL34 or GEC KT77 than to a Tung-Sol 6550 or any KT88, leaning toward quickness, dynamics, and bass control, rather than warmth, dimensionality, and bass weight. Listening to record 2 of Holly Cole’s Temptation, after listening to record 1 using the JJ E34L’s brought the differences into focus. The JJ’s were fuller, richer, had a bigger soundstage and more bloom, with more bass weight. In fact, too much bass weight, to where it was somewhat overwhelming and a little loose. With the Philips 6550 the bass was much more controlled, quicker and deeper, but some dimensionality and richness were lost in the process. I can’t say for sure which presentation I liked better, but on a Rob Mullins Audioquest record, the quickness, dynamics, and slam were fabulous with the 6550’s. I could hear a lot of detail in the bass, piano, drums, saxophones, and voices were great with these tubes. Again, they fell toward transparency rather than soundstage size. Highs were also well-detailed and extended. It is difficult to say how they compare in sound to most of my other tubes because so many things of my stereo have changed since I listened to the other tubes, but I will be trying the others in the near future. One thing is certain, I love the sound of these tubes.

Ei 6CA7: I bought these new production tubes from Upscale Audio without much background information, but thought I would try these tubes, which look like a scaled-down version of the Ei KT90. Unfortunately, I tried them right after the Philips ECG 6550, which are a tough act to follow. And I find the Ei 6CA7 to be a good-, but not great-, sounding tube. It’s not that they do anything wrong, it is that they don’t really do anything right, either. Dynamically, they are OK, but not anything special, especially compared to the Philips 6550, which was far more dynamic on Audioquest jazz recordings. Bass is OK, but not that extended nor punchy. Perhaps their best performance is in dimensionality, where the soundstage is big and clear, but images are not that tight or palpable. Highs are quick and clean. The midrange is fairly warm with an upfront perspective, but resolution is not these tubes’ strong suit: speed and detail are missing in action. I wasn’t enraptured by recordings the way I am by the better new production tubes like the Svetlana or JJ KT88 and JJ E34L, and certainly not by the likes of the best NOS tubes. I feel rather ho-hum about these tubes, which are in the same class as the Chinese KT88, Svetlana EL34, and Ei KT90.

Tesla KT88: I bought these tubes from ATSI, which were “on sale” below their “normal” price. According to Ken Chait, ATSI owner, and word on Audioasylum, this is the same tube as the highly regarded, but problematic, KR Enterprises KT88 so highly thought of by Dennis Had of Cary Audio. Ken says he has had only one failure in a big batch sent to him by Tesla. As far as looks, they are great; very clear glass with copper-ringed bases. In fact, they look a lot more like GEC KT66’s, with clear glass and slightly sloped glass bulges, rather than the more abrupt transitions of other KT88’s. And I will tell you what, these were a big contrast sonically to the Ei 6CA7. Where the latter are warm and bland, these are controlled and detailed. Listening to Audioquest jazz and a Nautilus pressing of Seals and Croft’s Summer Breeze, the amount of detail was elucidated. There was a delicacy of detail, an ease of presentation, a control that made it easy to follow individual instrumental lines. The bass was highly detailed and tuneful, highs were shimmering and well-defined, not white noise like on the Ei 6CA7. Dimensionality of the soundstage was superb, with great transparency and clarity, and instrumental images were well-formed. They were quick and dynamic, but not like that with the Sylvania 8417 or Philips ECG 6550. In fact, it was interesting how these 3 tubes, while all presenting a quick and detailed presentation with great transparency, they were quite different in other regards. The 8417 and Philips 6550 are propulsive and visceral, with explosive dynamics, especially in the bass. On recordings with low bass, the room seems as if it is moving around. If you want to hear bass dynamics like those of live music, listen to an Audioquest recording using these tubes. The Tesla KT88 is more refined, with delicacy, smoothness, and an ease of presentation, a more intellectual approach like with the GEC KT66. Bass is more defined and detailed, but much less weighty and extended, with much less slam than with the 8417 and 6550. Dimensionality is also better with the Teslas, which brought out voices well.

Visseaux 6L6G: I had read about these on Audioasylum as being very superior 6L6 versions, but I had never seen one until KCA tubes listed them. They have a retro look, with a tubular glass envelope, and look like some tube out of your grandfather’s radio, which they indeed might have been, as they were made in the 1950’s. And the inmates were correct, this is definitely a sleeper tube. They have a big, upfront, dynamic sound with a big soundstage, good detail, and deep and defined bass. Highs have that burnished brass sound rather than bursts of undefined white noise, and are upfront and prominent. Bass was definitely tuneful, punchy, and deep, although extension and dynamics not quite to the level of the Philips ECG 6550 and Sylvania 8417. The soundstage is big and wide, but perhaps not as dimensional as the better KT88’s, 350B’s, or Tung-Sol 6550. They are definitely dynamic, as indicated on Audioquest jazz recordings, and their quickness was a delight. The sound was a lot more visceral and palpable than the Tesla KT88, whose sound is completely different than the Visseaux. Detail and transparency-wise, the Visseaux 6L6G’s are very good, but perhaps edged slightly by the Tesla KT88, GEC KT66, Amperex Double-D EL34, and, of course, the detail king, Sylvania 8417. These things make the Ei 6CA7 seem like a joke. And these are low-power tubes to boot, but they sure don’t sound it.

Mullard xf1 EL34: I finally bought a quad of these expensive things from KCA Tubes after nearly mortgaging the house, biased at 50 mA, fired up an Audioquest pressing of Bruce Katz Transformation, and Whammo! Huge dynamics, tight and punchy bass, big soundstage, prominent and burnished highs, lots of detail. Man, these things are awesome. Dynamics, both in the bass and midrange, are explosive, like those of the Philips ECG 6550. Bass is extended and detailed. On cymbals, they were right there and shimmered like brass. The soundstage is far and wide, and dimensionality good, but perhaps not like a good KT88, --what else is? However, KT88’s don’t have detail and dynamics like the Mullard EL34. Saxophones honked and drums snapped like in real life. The sound is definitely upfront and immediate, full and smooth, more so than the Visseaux 6L6G, and dynamics are somewhat better. The Visseaux trades these attributes for more soundstage detail and dimensionality, but the Mullards are definitely not lacking in any of these areas. Tonally, the Mullards are on the warm side, perhaps not like the Visseaux 6L6G or any of the KT88’s, but not lean like a GEC KT66, Sylvania 8417, or Ei KT90. And whoever says the Svetlana EL34 is up to Mullard xf1 EL34 standards has been smoking something funny. Even the JJ E34L is considerably better than the Svetlana, but the Mullard and Amperex, as usual with NOS versus new production tubes, are somewhat better than both the Svetlana and JJ.

Tube
Detail
Dimen

sion

ality
Sound

Stage
Clarity
Imme-

diacy


Dyn-

amics
Bass

Ext-

ens
Bass

Tight

ness
Bass

Dyna/

Wgt
Highs
Tonal

Balance
Ease

Of

Present

JJ

KT88
2
3
4
2
3
2
3
2
2
3
3
3

JJ

E34L
3
3
4
3
3
3
3
3
3
3
3
2

Sylv

6CA7
3
2
3
3
3
2
3
2
2
3
3
3

Phil

6550
4
3
3
4
3
4
4
3
4
3
3
2

Ei

6CA7
1
1
3
2
2
1
1
2
1
3
2
3

Tesla

KT88
4
4
4
5
3
1
2
4
2
4
3
4

Viss

6L6G
4
3
3
3
3
3
4
3
4
4
3
3

Mull

EL34
4
3
3
4
4
4
4
3
4
4
4
2

GEC

KT88
3
5
5
3
4
3
3
2
2
3
3
5

Amp

EL34
4
3
4
4
4
4
4
4
4
3
4
2



Mull

EL37
4
4
4
3
4
3
4
4
3
4
4
3

NU

350B
3
5
4
3
4
3
3
3
3
3
4
5

GEC

KT77
4
4
4
4
4
4
4
4
4
4
5
3

RCA

6L6G
3
3
3
3
3
2
2
3
3
4
4
4

Chin

KT88
2
3
3
2
3
2
3
2
3
3
3
2

Svet

KT88
3
4
4
3
3
3
3
3
3
3
3
4

GEC

KT66
4
3
4
5
4
2
2
3
2
4
4
5

Syl

8417
5
4
3
4
4
5
5
5
4
4
4
3

T-S

6550
4
4
5
4
4
4
4
4
3
4
4
4

Ei

KT90
4
3
3
3
2
4
4
3
2
4
3
3

Svet

EL34
3
3
2
3
3
3
4
3
3
3
3
2

JJ KT88: 2.67

JJ E34L: 3.00

Syl 6CA7: 2.67

Phil 6550: 3.33

Ei 6CA7: 1.83

Tes KT88: 3.33

Vis 6L6G: 3.33

Mull EL34: 3.58

GEC KT88: 3.42

Amp EL34: 3.67

Mull EL37: 3.67

NU 350B: 3.58

GEC KT77: 4.00

RCA 6L6G: 3.08

Chin KT88: 2.58

Svet KT88: 3.25

GEC KT66: 3.50

Syl 8417: 4.17

T-S 6550: 4.00

EI KT90: 3.17

Svet EL34: 2.92

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