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I just won on Ebay these 3 NIB Hitachi 6SN7GTB black plates (re-branded as Tel-Rad) These are the bottom square getter ones vs the more common top getter ITT branded Hitachi version. Lots of posts here on the Hitachi's, but often it's not clear as to which of these two types are being discussed. If anyone has this Hitachi version, I would love to hear your opinion on these. I will post mine when they arrive.
Also, the date code is 8-8 as stated by the seller. Hard to find ANY Hitachi date code info, so if anyone knows that would be of interest also.
Your letting our secret out concerning the quality listening available in Japanese tubes :) BTW, if you like those tubes when they come in the mail, I see there is a lone tube on ebay being sold as a " Raytron 6SN7GT " It is being sold " as is " But the price isn't bad. Not sure what yours looks like from the top, but it appears to be the same as yours. I have a bunch of Japanese tubes stamped " made in usa " but clearly Japanese. Strange what companies did back then.
Speaking of Bad Boys: I purchased 6 pair of these tubes in the pic about 10 years ago for $16 a pair! I still haven't figured out what they are other than something out of the 50s-60s era. They are labeled Haltron, so they could be from anywhere. My guess is they are Russian. I can tell you they spanked the Bad Boys in a A/B test in my pre!
You may be right about keeping quite about Japanese tubes. There is still a good amount of "snob" bias out there from many I'm sure have not even given them a try.
The tube you posted is not the same tube as the Hitachi's I have. My pair is already in my headphone amp, or I would take a close-up. So I copied two photos from the web that shows the construction and are posted above.
I spent a good amount of time checking EVERY detail of the internals of the Tel-Rad labeled ones I purchased. Also, the print on the base (6SN7-GTB) has a distinctive print style of letters and numbers, and the Tel-Rad and Hitachi are a match there also.
Who is making a 6SN7 headphone amp?
I have a Woo Audio WA6 which I purchased new in 2012. It came with two 6DE7s and a 274 rectifier. However, it can use a pair of 6SN7's with socket adapters ( available from Wood Audio ) which I purchased two of at the same time, as I intended to use the 6SN7 from the get-go. I prefer the 6SN7 over the 6DE7, not to mention there are way more 6SN7 tube options vs the 6DE7. I also use a 1961 vintage Mullard GZ34 for the rectifier position. I love this tube amp and it drives both my Dennon AH-D7000 and Sennheiser HD600 phones very well.
Some other 6SN7 headphone amp makers I know of ( past and present ):
1. Darkvoice 336i ( discontinued )
2. Darkvoice 336SE ( Currrent model )
3. Single Power PPX3 ( discontinued )
4. Dragon Inspire IHA-1 ( Current model , but not cheap @ around $1600 )
I have heard both the Darkvoice units, which are decent sounding enough, but I prefer the Woo Audio WA6. For what it's worth, a new version of the Woo Audio WA6 came out this year and no longer supports 6SN7's from what I understand.
Don't know what to tell you about sound difference ( different or not ) as far as getter placement. I have never designed a vacuum tube. I can say that I have rolled just about every 6SN7 tube ever manufactured. Most in the same preamp. The same brand tube with different getter placement did, have a, different sonic signature. Couldn't say whether that actually is the getter, the composition of the rest of the metal, size of bottle, etc, that makes the difference. I simply know that there is a difference in same brand tubes with different getter placement. Therefor I made my notes by where the getter was. Seemed the simplest way-
A note... Raytheon 12BH7 had a definite different sonic signature. Depending on if they had a square getter, or a round getter. Go figure
Other than known and measurable electrical properties that we know effect performance, I do agree that there are no absolutes when it comes to exactly which internal parts can contribute to sonic differences in the same tube type, even from the same manufacture with identical production dates. I have a pair of Sylvania 6SN7GT 3 hole bottom getters, the so called "Bad Boys" dated from 1951. The tiny but known difference in the construction between those and the 2 hole does indeed contribute to more deep bass and a slight improvement to the top end sparkle over the otherwise identical 2 hole plates. Those who wish to argue otherwise feel free to do so, but my ears sure know the difference.
I have a pair of National Union 6SN7GT's that I purchased NOS, have the same date code, and measured the same on my Jackson Tube Tester. But they sound a bit different from each other. It's not huge, but it's there.
I too have a decent size collection of 6SN7's, including most of the agreed upon top recommended choices from around the web. These Hitachi tubes can really hold their own. Those who wish to dismiss Japanese tubes as inferior without listening to them are missing the boat. I already count these Hitachi tubes among the top 5 of my favorite 6SN7's and are also the only GTB issue 6SN7's that I really like.
The happy (or sad, depending on one's prejudices and viewpoint) fact is that probably it doesn't make the slightest bit of audible difference whether the getter is at the top or the bottom. Of course, you will almost certainly hear people claiming that one, or the other, has better "soundstaging," or something like that. Unless it could be demonstrated in double-blind testing, it doesn't count for anything.
As far as getter location, I only pointed it out as a visual way to differentiate this Hitachi 6SN7 from the other more common version, as there appears to be just these two types of Hitachi 6SN7's. The top getter tube seems to have been made with black or grey plates, and also has a Toshiba version that appears identical. I think all would agree that no matter how identical tube construction appears between different manufactures, the sonics can be very different.
I have not heard the top getter Hitachi and the more common ITT/Hitachi branded one of the same tube, but most owners say it leans towards a warm overall presentation. I did find two comments from owners of the type I just purchased and their take on the sonics is much like mine. Both those reviewers said this bottom getter black plated tube is one of their favorites, as it in likely to become one of mine.
I seem to remember having some of these branded " Raytheon " They sounded better than new production. But I guess what you are putting them into will determine how they sound to you. Not sure if they were out of out of Japan.
Most 6SN7 Japan tubes I purchased had the top circle halo. These sound sweeter than yours did to me. I thought the type you have were a bit more forward sounding. May still have some of both types of these, but all my tubes are packed as I'm in the process of moving.
Japanese did make some nice tubes in the late 1950-70s. I'm not familiar with their 6SN7GT. But, do have a stash of Raytheon labeled 12AX7A and some 5AR4/GZ34 tubes.
These are indeed Japan made by Hitachi, and also were sold and labeled under the Hit-Ray brand, which was the joint agreement between Hitachi and Raytheon. The label on mine ( Tel-Rad ) was the logo for Telrad International, a communications company based in Richmond, BC Canada. The date code would seem to be 9-8, printed on the tube. Still not certain if it is 1958 or 1968.
I gave these a few hours of warm-up and a 2 hour listening period. My initial impression is they sound somewhat like a cross between Ken-Rad and early Sylvania bottom getter 6sn7's. Very good detail, a bit forward in the mids, excellent deep bass that is not flabby, and extended highs without a hard edge.
However, I would say that the most impressive trait of these tubes is the amazing dynamics and fast transient speed. Almost solid-state fast! Percussion is taunt and punchy, as is the deep bass. Pretty decent soundstage too, although not as much as my Sylvania or Brimar 6SN7.
If your using 6SN7's and your taste leans towards less warmth and better clarity, you might well want to try these. I do know that these bottom getter Hitachi tubes are rare and less common that the top getter versions.
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