[gibosi]

Sylvania 6HZ6 (and probably the Sylvania 6DT6 as well)
 
In order to get a handle on the sound of this tube, I pulled out the Sylvania 5915 (a premium version of the 6BY6) to compare. For those just joining us, this tube first came to our attention wearing Telefunken paint. Dubbed a "Tele/vania" by Audiofanboy, this is an excellent tube. You can read more about it here and here
 
Now my Sylvania 5915 are wearing plain-jane Sylvania paint, not the fancy Telefunken paint, but inside they are identical to the Tele/vanias.
 

 

 

For both tubes, I used the EF95 1-7 configuration. Initially, my old ears could not discern any significant difference between these tubes. Both have strong, detailed bass, clear vocals that are less warm than the RCA and Tung Sol, and open and airy highs with great detail. But then I remembered Audiofanboy's comments about the Tele/vania's sound stage on Dreams from Fleetwood Mac's album Rumors, and I added it to my play list. 
 
While both of these tubes have a very wide sound stage, the 6HZ6 seems to be a bit more two dimensional, whereas, the 5915 is more three-dimensional. With the 6HZ6, vocals are right in your face, but with the 5915, vocals and instruments seem to be a tad bit farther away and there is a very real sense of 3D space. As Audiofanboy put it, a "boundless" sound stage.
 
So while the Sylvania 6HZ6 is still a very good tube, I have to give the nod to the Sylvania 5915 due to it's superior staging. And if you do not have this tube in your collection, I encourage you to get a pair.

 

[Iron58p]

Are the same Gibosi ?
 
http://www.ebay.it/itm/TWO-5915-SYLVANIA-TUBES-N-O-S-/261257069567?pt=Vintage_Electronics_R2&hash=item3cd42283ff
 
i have buyed

 

[duncan1]

In answer to you all= A HEXODE has 4 grids+plate and cathode= 6 electrodes. A HEPTODE has 5 grids+ plate and cathode=7 electrodes--You cannot just change an INTERNATIONAL agreed  tube recognition formula that the World of EEs has designated by saying- grids 2+4 are tied together so that make it one -Wrong!  This is in the Mullard/ osram/philips/rca/etc  tube books - Its a FACT 

 

[foreign]

I'm currently burning in a pair of Hytrons 6ak5 has anyone tried these before and if so what is your impressions??

 

[gibosi]

Quote:

Are the same Gibosi ?
 
http://www.ebay.it/itm/TWO-5915-SYLVANIA-TUBES-N-O-S-/261257069567?pt=Vintage_Electronics_R2&hash=item3cd42283ff
 
i have buyed

 
Yes, these are the same. Enjoy!

 

[Iron58p]

I'm very happy
 
Thank you very much !!
 
Really, for the moment i can't enjoi anything, i have only the stock Valvo 6CQ6 ( that i think have problems to be red and not hot ), in my home

 

[Oskari]

Quote:

Mikelap, great pics of both tubes! So, can we conclude that they're the same? Have we solved the Siemens mystery? Are those foreign Siemens just Japanese Matsuschiita tubes?

 
Actually, I think they were made by Toshiba.
 
Quote:

 
The type does not appear in the Matsush¡ta catalog but does appear in the Toshiba catalog.

 

[Audiofanboy]

Quote:

 
Actually, I think they were made by Toshiba.
 
 
The type does not appear in the Matsush¡ta catalog but does appear in the Toshiba catalog.

 
Actually, I believe you may be right or at least close.
 
I read that long Matsu catalog yesterday, and the types (look at the picture of 12BE6 -12V version of a 6BE6- on page 16) that are similar to 6CS6 tubes don't appear to look like those Siemens-ish ribbed tubes. They look like Mullards, and they should, since that's the factory tooling they had bought, or so say many people.
 
Now, I don't know what the link could have been between Toshiba and Siemens -or if they even was one- or if this is just another story of factory lines and tools going from Europe to Japan in the later tube manufacturing days.
 
I know that Siemens has had links with Fujitsu though -hence the company name for some products- but I haven't looked at when that dates back to, or whether or not Fujitsu ever made tubes.
 
Fascinating stuff really.
 
So, do these 6DT6 tubes I bought look Siemens-ish to you? Or Toshiba-ish I guess?
 
Edit: Actually, the Japanese 6CS6 and 6DT6 I bought were definitely manufactured by Toshiba, no doubt about that. Just look at a few pictures of similar or remotely close tubes made by Toshiba on google or ebay, and you'll see those ribs on the plates and the same construction. Toshiba made tubes for a bunch of companies in the late tube days apparently: ITT (one 6DT6 on ebay has those ribs), HP (yeah, computer-rated tubes!), and other specific companies like Tektronix (and yes, you can find Tek-matched tubes) or some weird organ-makers and guitar amp makers. Anyway, all the similar tube types I saw look the same.
 
Now, why do they look the same as Siemens branded tubes?I just can't see the pattern here. That Siemens evantually sold 80%+ Philips tubes and some odd-ball Japanese tubes for the last dozen percents just doesn't make much sense... Not with the cheap East German stuff they could get much closer. That some cheap cheap relabeler Haltron or Zaerix tubes be Japanese makes sense, but that a few lonely German brand tube be does not. Still, unless Toshiba somehow bought some German tube-making gear in the 70s, that's how things are looking right now.

 

[Oskari]

Quote:

I read that long Matsu catalog yesterday, and the types (look at the picture of 12BE6 -12V version of a 6BE6- on page 16) that are similar to 6CS6 tubes don't appear to look like those Siemens-ish ribbed tubes. They look like Mullards, and they should, since that's the factory tooling they had bought, or so say many people.

 
True.
 

I know that Siemens has had links with Fujitsu though -hence the company name for some products- but I haven't looked at when that dates back to, or whether or not Fujitsu ever made tubes.

 
If you are thinking about Fujitsu Siemens Computers, that was much later. Fujitsu Ten certainly made tubes.
 

So, do these 6DT6 tubes I bought look Siemens-ish to you? Or Toshiba-ish I guess?

 
Indeed.
 

1. http://goods.ruten.com.tw/item/show?11091126815870
2. http://articulo.mercadolibre.com.ar/MLA-456642910-valvulas-electronicas-6dt6-nos-nib-toshiba-japon-_JM

 

That some cheap cheap relabeler Haltron or Zaerix tubes be Japanese makes sense, but that a few lonely German brand tube be does not. Still, unless Toshiba somehow bought some German tube-making gear in the 70s, that's how things are looking right now.

 
Why not? It's just business after all.

 

[Audiofanboy]

Quote:

 
True.
 
 
If you are thinking about Fujitsu Siemens Computers, that was much later. Fujitsu Ten certainly made tubes.
 
 
Indeed.
 

1. http://goods.ruten.com.tw/item/show?11091126815870
2. http://articulo.mercadolibre.com.ar/MLA-456642910-valvulas-electronicas-6dt6-nos-nib-toshiba-japon-_JM

 
 
Why not? It's just business after all.

 
I have actually seen TEN -the brand- tubes, and they look different from the Toshiba. I ruled out Fujitsu being a possibility the second I took a look at Toshiba tubes... So minutes after I wrote that comment.
 
About Siemens supplying Japanese tubes, it just surprises me a bit that they would do so in that time frame. Actual Siemens tubes, like olde worlde Siemens & Halske double triode types are typically well regarded, which leads me to think that the Siemens company had fairly high standards, kind of like Telefunken. So, either it means that by the 70s, they just didn't care much about quality anymore, or it implies that Toshiba tubes were at least OK (Hewlett Packard used them so they couldn't have been horrible; they sound good at any rate), or of course none of these were considerations and it's just basic business as you say. I guess my view of the tube times is the same as my world view: a bit manichean...

 

[mordy]

Did not find much in trying to research Japanese tube manufacturers (Hitachi has not been mentioned yet). However, I found this example of a Toshiba tube radio. IMHO the design is absolutely beautiful.
 
 

 

 

[Audiofanboy]

Quote:

Did not find much in trying to research Japanese tube manufacturers (Hitachi has not been mentioned yet). However, I found this example of a Toshiba tube radio. IMHO the design is absolutely beautiful.

 
It's funny you would mention that picture mordy, as, looking at it an hour ago on google, I was just thinking to myself: "Wow, what a nice looking radio! How long before some manufacturer copies that design on some random neo-retro Apple-like product...?"
 
It does look nice though. A lot of people actually buy old radios like this one, empty them from their original contents, and just use the case for some other -assumingly- audio role.

 

[mordy]

"Great minds think alike" - lol
 

 

[Acapella11]

Quote:

EH90 VS 6DT6

I have been rolling tubes like a madman lately, and I figured I'd share my notes on what are in my opinion the best tubes for the Little Dot 1+ we all so love!
 
...
 
Early Conclusions
 
These are easily the 2 best tube families out there for Little Dot amps... so far... I will be keeping at least a pair of both families! More to come this weekend (more 6dt6's incoming)

Great contribution kvtaco17. When going through the first two songs with my Blackburn Valvo EH90 strapped, unstrapped and 6/7, I was quite surprised how differently the songs changed with the straps. And I could exactly understand why you preferred unstrapped over strapped in "Taking a chance on love". I would choose the same. In the first song (Moonshine) 1/7 and also 6/7 do work better. I like when head-fiers post music, because you always discover good new music. Good thing, there were even quite a few tracks to go through.

My impression is that the EH90s are a bit lesser ambience tubes but rather have their strengths in detail and tonality. I haven't heard the 6DT6 yet but they seem to go more into the Siemens EK90 (black bottom) direction, which I have as in they are a tad warmer and give a good spatial impression. If this is the case, then these will shine in occasions where the recording is favourable towards the perception of the room and the EH90s play out better when the room itself doesn't really come out that well but it is rather about the more forward placed instruments / singer. Just a consideration.

 

 

Mordy, how do your power tubes along? Just curious since you had them already a while.

 

 

Oh, one more recent finding. When going back to the special quality 6BE6 tubes, I kind of re-discovered the Sylvania JAN 5750. I didn't like them much on my old setup with the HE-500 and a darker cable. If your setup is bright enough to to fit a really dark tube, then these Sylvanias are highly recommended. Amazing imaging and extremely large stage. Very well articulated bass. One of best instrument separation I have heard. 1/7-strapping opens them up but makes them also sound more forward, such that you lose ambience. Seriously good, dark tubes.

 

[kvtaco17]

The Sylvania 6DT6's came in today! Burn in starts now!
 

 
Initial impressions (1hr of run time) are similar to the RCA's but with less bass and maybe the illusion of better treble detail, and a better focused sound stage.
 
EDIT
 
The bass showed up just short of 3 hours... Very similar to the RCA's, with a touch more treble.