If the TU-8200DX really does pair well with headphones of lower ohms, it would be very cool. I do plan on obtaining at least 1 new headphone in the next 6 months, but probably either a medium or high ohm model, so we'll see. As far as something like an IEM, which I personally would never use with this amp on purpose, I'm not too sure... might be some hiss; it would be quite the feat if it did though!
It's nice having someone like Victor so close, as shipping and import is much cheaper. I wish it was a little more feasible for you, as it is a very nice amp.
As far as tube rolling differences, I actually mean both differences, between variants and brands that are both more impactful; however it comes in varying degrees of impact, so it would help if I clarify.
An analogy of these differences I could try to use, would be similar between different types of cable changes, where some can have more of an impact than others seem to. I would say that the differences in brands, but same make of tube, are generally much more subtle than differences between different labeled designs. Such as the differences one might find between 2 really good RCA cables of similar material. While the differences between actual variants is more discernible and I find is easier to detect. More of like going from the stock power cord to a nice high end power cord of good quality materials. I would say that I've found the effects are generally twice to close to three times as impactful between variants than between most brands of the same. Of course, everyone's mileage will vary by system and I've also not not always found this to be the case; the automatic bias feature of the TU-8200DX does make auditioning these many variants easier. However, the sound quality has always been very good with the tubes that I've tried so far, just interesting alterations between them, that I believe is due to the greater resolution of the amplifier when compared to the 336se.
There are a ton of tube-rolling threads out there over sonic differences between brands, but I've often found that it is best to let my own ears decide sometimes and will try any manufacture at least once. I do believe that everything from the materials used, to the fitting of the factory, and especially design can lead to differences in characteristics; how small vs. big these differences are is dependent on many things. There are a ton of ways manufactures designed their tubes in the day, even within the same family/brand, usually at least distinguishable by the years of production. Some specific factories, such as Mullard's Blackburn, tend to give more resolution/detail than Mullards made elsewhere, as their factory in India. Everything from plate structures to getter shape/location all seem to have an influence on the signal, I guess it makes sense, since the tube is in the path of the music. If this wasn't the case I've found, my wallet would be a lot happier!
There would also be no need to switch out the stock tubes, or run a Bendix 6080WB or GEC 6080, rather than a GE 5 Star 6080 or run of the mill RCA, which in my opinion can sound very thin often.
As far as the impact between rolling the 336se to the TU-8200DX, I believe what I'm hearing is partially due to the better separation between the channels in the TU-8200DX. That the added silence, detail, and resolution from the Elekit has made the sonic differences more distinguishable than before, at least for me. At times, it has made me wonder if I was ever truly getting all the differences between the different brands/designs of 6SN7s in my 336se because of some congestion/bloat. I never felt much congestion nor bloat with all of the tubes I've tried so far in the Elekit, unlike a few with 336se. Also, during the burn-in period these differences were much more pronounced and since have smoothed out quite a bit; blending in better and are now a little harder to pick out. I use a selection of 15 to 30 seconds clips that focus on some of the sonic aspects the tubes seem to impart on the sound; some show me lower mid-range resonance levels, while others sound stage/imaging, and even a few I use to test high frequency, such as the crispness of a cymbal crash and the layers of resonance that follow; I also find that even voices are very good for testing. Over time, consistent use of these test tracks has given me a better baseline to judge between various brands, which isn't always an easy thing to do.
I have spent some time with 6AS7G/6080/5998, as it is the power tube in the 336se as well, but unfortunately there isn't huge copious amounts of different types of this tube to roll out there; there are still a few though. The 6AS7Gs are almost all RCAs, with a few being made by tungsol/chatham for military use. There is a small difference in the mids/bass between the black and gray plates, with the gray plates being a little softer around the edges with better mid range and sound stage; the black plates are older with silver lettering, while the more recent production gray plates have orange lettering. I find that the bass is somewhat lacking on the gray plate RCA, with the black having better weight. The 5998 is almost exclusively Tung-sol with re-brands by Chatham, which I find is more in line with the sound of the 6AS7G than the 6080, but with deeper bass, extended highs and more weight to the sound. It is hard with the 5998s, as they also give a bump to the overall gain, so everything is more pronounced unless adjusted. The 5998 are great for slam and dynamics, but lack overall air and depth many times, IMHO. I find that neither of these can touch the sound stage and air of the 6080 though, with an exception maybe with the RCA gray plate. I do find the 6080s to be more polite, but with added air as well as bloom, if at the expensive of slam and weight, especially compared to the 5998. You really have to be a little careful though because I've found that several brands/batches of 6080 are a little light in the low end. I've never liked the GE 5 Star and RCA (except for older JAN RCAs) for this reason, and while the Tung-sol and Bendix WB build with cast iron plates can give nice highs, great mids, and enough bass for most music, at times they can sound a little thin in the upper mid-range. For 6080, I prefer the mids and extra airiness from the European variant, the CV2984, with Brimars and British Military being very nice if you can find them. Then there is the GEC 6AS7G, with comes as a coke bottle as well as a 6080. I purchased one about 5 years ago for a great price, at $80 shipped NOS, however it was damaged in shipping. Supposedly they have the same internal structure, but the coke bottle 6AS7G generally commands higher prices. I wish there was a little more variety with the 6AS7G type, but the 6sn7 is truly a monster when it comes to different brands/builds and one of the main reasons I bought the amplifier and have kept it for so many years.
The 6sn7 has a ton of brands/designs, which makes it a favorite tube of many rollers. Within the 6sn7 type there are different designations separating designs by the addition of functionality and/or purpose. Some have heaters and warm up quicker for example. While there are differences between these types (designations GT, GTB, A, W, etc.), different brands/years used not only different components/designs, but also different materials. All of this can affect the sonic characteristics of the sound, but I've found that price isn't always a true determinative value of quality; like a lot of things. Many tubes that I purchased on the cheap have really impressed me, at least in my system and to my ears. Some are definitely worth their money, such as the Tung-sol Round Plate, or the metal based and plastic short bottle 6SN7W, which can really go for a lot. However, others such as the early Hytrons/CBS, or the militarized
micanol bases can be had for cheaper prices and still sound very good. For example, one little generally unknown tube, the 60's Brazilian Aluminum RCA 6sn7gt, is very different than any other 6sn7 I've tried, closer to the Tung-sol "Mouse Ears" than anything else, but still very different. This Brazilian metal design can add a ridiculous amount of air and seems to push the sound out in all directions by many feet; very good with chamber/orchestra and even live acoustic. Then there is the European variants like the CV1988 and B65. I've never had the pleasure of trying a B65, such as the Osram/Marconi brands, as they can be very expensive. I do have a Brimar CV1988 black glass that has very good mids, but seems to cut off too much of the highs and also be a bit sibilant. Others can work in place of the 6SN7, such as the ECC32 and ECC33, in most applications, with more impactful differences than within same family.
The 6AS7G/5998s really don't have a whole lot of different manufacturers out there, at least compared to others, there is more as a 6080 variant, but still not a ton. On the other hand, the 6SN7 is a widely popular tube, even during it's day, and was made by many different manufacturers/brands, which in most designs/brands provides enough variation to warrant large tube threads/discussions/rollers, not to mention the varying degree of prices asked for on-line and in auction. However, I do believe everyone's mileage may vary as ears and systems are different. There are also a lot of re-branded tubes that not only sound exactly like their OEM brothers, but because so generally go for cheaper prices.
As far as the TU-8200DX, there are a ton of different actual variants of tubes you can use, regardless of brands, and the differences between them are not always subtle at all. The KT series sounds very different to the EL34, or even the 6L6CG. However, at times I've found differences even within manufactures, with the blue glass Telsa EL34 being much brighter up top with great air, but a little thinner and lighter in the low end than the Tesla yellow seal clear glass. GE and RCA 6L6GCs are similar, but the GEs tend to have quite a bit of bass compared to the RCA, which I found is more balanced, similar to the 5998 and what it does to the speed and articulation of the notes. Within these types there are also many new production tubes, some of which are really only geared to guitar amps, which can really eat up tubes during live shows. Since they are constantly going through them, they need more inexpensive new production brands. Most of the time these are Russian, such as Svetlana's, JJ's, or the re-branded Tung-sol's. Others such as the Russian re-brand of Genalex's Gold Lion brand give better sound quality, but at a higher price. Russian manufacturers bought the rights to use the names of classic out of production NOS types, building them to the specifications of the original designs (or at least they claim). However, many believe that most of these do not sound as good as their original NOS counterparts, and the cheaper brands aren't seen as reliable. Many like the Russian Gold Lions, as an inexpensive alternative to the NOS original. The KT88 GEC's or original Gold Lions can bring large prices at $200-$300 a tube, which is a product of both their scarcity and sonic enhancement; arguments for both. Other new production, such as Psvane and Shuguang Treasure ask higher prices for claimed higher fidelity; many have had great results.
There are also many variants for the 12au7 and even more brands, which can either be dirt cheap or command very high prices. With the TU-8200DX, I find that the differences between signal tubes can vary from subtle to slightly impactful, with again the more impact coming from variants than individual brands. The Tung-sol black glass provides a very nice full sound, while some of the GE's can sound a little thin. I've also enjoyed the CBS/RCA black plates, with the RCA clear glass being very clear and detailed, but a little thin with certain songs. Then there are the variants, such as 12au7a, 6189, 5963, 5814, 7730, 6680, ECC802S, 7136, ECC82, 13D5/4/8, and probably a lot more I missed. Within a few of these variants there is only really one brand, sometimes with a few re-brands, but generally the 12au7, 12au7a, 5814, and ECC82 have quite a few brands. Another example, I've been using some Tesla silver pin ECC802S recently and rolling Siemens, Valvo, Mullard, and Philips EL34s; I'm getting some really great smooth detail with great clarity in the mid-range, very nice. There are the more expensive Telefunkin gold pin ECC802S, that are supposed to have better clarity, but only these two brands. While the different brands of EL34s listed all have varying degrees of detail, air, and sound stage in the mids/highs, but not huge differences. So, a bigger impact to what I'm currently hearing would be to change to say a KT88 and a Mullard Blackburn ECC82. I believe this is due to the increased resolution of the TU-8200DX over the 336se, as the differences between these similar EL34 brands seem to have more of an impact than say a GE 6080 5 Star gray plate and an RCA orange label black plate 6080. Now, putting in a Telefunkin EL34 or a SED Winged "C" or even a Groove Tube, will give me a more intensely different flavor.
From my experience, I would say that it depends on the types of tubes used and the resolution of the amplifier in the end, which both are a testimate to good design. Some designers have chosen to go with newer production tube implementations, utilizing new production Chinese and Russian types, while others have kept the NOS market very much alive today by choosing types such as the 6sn7 and 6AS7G. With a ton of NOS options as well as plenty of new production today, I'm sure glad Mr. Fujita picked the ones he did for the TU-8200, even though my wallet may not be...
