For 6BL7 tube users

[Nelco]

On the subject of 6BX7's a little while ago i purchased 3 Westinghouse branded tubes of this type for a modest sum. All tubes came in Blue and White Westinghouse branded boxes. One of the tubes seems to be a GE tube but the other two have no markings at all anywhere on the tube other than the Westinghouse branding / tube type on the base and I have no idea what they are so am hoping someone more knowledgeable can help identify them.

Tube no 1 has Halo getter support, double mica, non copper rods (steel?) and grey plates
Tube no 2 has Halo getter support, triple mica, copper rods and black plates


Tube no1

Tube no2

All thoughts gratefully received..............................

 

[gibosi]

On the subject of 6BX7's a little while ago i purchased 3 Westinghouse branded tubes of this type for a modest sum. All tubes came in Blue and White Westinghouse branded boxes. One of the tubes seems to be a GE tube but the other two have no markings at all anywhere on the tube other than the Westinghouse branding / tube type on the base and I have no idea what they are so am hoping someone more knowledgeable can help identify them.

Tube no 1 has Halo getter support, double mica, non copper rods (steel?) and grey plates
Tube no 2 has Halo getter support, triple mica, copper rods and black plates


Tube no1

Tube no2

All thoughts gratefully received..............................

Tube no1 is a later Tung-Sol. The earlier ones had black plates and mica spacers with 8 equally spaced teeth, top and bottom. And tube no2 is a Sylvania.

 

[Nelco]

Many thanks indeed Gibosi, much appreciated. Any idea as to a rough date of manufacture and why it would be completely unmarked by the original manufacturer?

 

[mordy]

Many thanks indeed Gibosi, much appreciated. Any idea as to a rough date of manufacture and why it would be completely unmarked by the original manufacturer?

Perhaps you can find some markings on the glass by looking carefully under good light and holding the tube at different angles?

 

[gibosi]

Many thanks indeed Gibosi, much appreciated. Any idea as to a rough date of manufacture and why it would be completely unmarked by the original manufacturer?

Westinghouse never made the 6BX7 and it would appear that it wasn't important to them to to date their rebrands. Further, many manufacturers used date codes that are largely indecipherable given that they were used primarily for warranty purposes. So often all we have to go on is the construction. Generally, halo getters were introduced around 1960. Further, Tung-Sol and RCA did not manufacture the 6BX7 until around 1960, so older ones, especially those with rectangular getters, were made elsewhere, usually GE and Sylvania, and simply rebranded. And then, having a bunch of Tung-Sol 6BX7, I know that that black plates are older than gray plates. But this pretty much sums up all I know. lol

 

[Nelco]

Perhaps you can find some markings on the glass by looking carefully under good light and holding the tube at different angles?

I did try with both white and UV light but i can't see any markings. I would have expected country of manufacture at least but nothing.

 

[Nelco]

Westinghouse never made the 6BX7 and it would appear that it wasn't important to them to to date their rebrands. Further, many manufacturers used date codes that are largely indecipherable given that they were used primarily for warranty purposes. So often all we have to go on is the construction. Generally, halo getters were introduced around 1960. Further, Tung-Sol and RCA did not manufacture the 6BX7 until around 1960, so older ones, especially those with rectangular getters, were made elsewhere, usually GE and Sylvania, and simply rebranded. And then, having a bunch of Tung-Sol 6BX7, I know that that black plates are older than gray plates. But this pretty much sums up all I know. lol

Many thanks for the insight, certainly a lot more than i knew
Knowing now that they are legit tubes and not likely to fry my equipment i swapped out the GE for the Sylvania. The GE had suddenly developed an extra smear of flabby bass between listening sessions. Not unpleasant but noticeable. Not sure if Tube just burned in now or degrading in some way. Anyway the Sylvania sounds very nice indeed, very similar tone to the GE but a touch clearer and bass now less flabby. Interestingly i also swapped the CIFTE 5Y3 GB coke bottle rectifier for a Phillips 5Y3 GB flat sided and this has made a big difference to the sound. Phillips tube much more transparent, less coloured and less pleasant sounding to my ears. Perhaps it will change over time but other 5Y3 GT tubes i've used i've not really been able to tell any difference between. Not so with the Phillips tube.

 

[mordy]

Many thanks for the insight, certainly a lot more than i knew
Knowing now that they are legit tubes and not likely to fry my equipment i swapped out the GE for the Sylvania. The GE had suddenly developed an extra smear of flabby bass between listening sessions. Not unpleasant but noticeable. Not sure if Tube just burned in now or degrading in some way. Anyway the Sylvania sounds very nice indeed, very similar tone to the GE but a touch clearer and bass now less flabby. Interestingly i also swapped the CIFTE 5Y3 GB coke bottle rectifier for a Phillips 5Y3 GB flat sided and this has made a big difference to the sound. Phillips tube much more transparent, less coloured and less pleasant sounding to my ears. Perhaps it will change over time but other 5Y3 GT tubes i've used i've not really been able to tell any difference between. Not so with the Phillips tube.

In terms of identifying tubes without markings I have found it useful to scroll through the offerings on eBay and look at the pictures for identification.
Another way is to go to Google Images and type in the tube designation - usually there are many pictures and links to websites together with the pictures and it can be very helpful as well.

 

[Designsfx]

@mordy / @gibosi
Thought I would jump in here with a quick post and story as this thread hasn’t seen much love lately. This last weekend I was at a swap meet here in the LA area seeing what I could dig up. There was a man there who had row after row of tubes- literally thousands. He walked out to meet those browsing the tables and would tell everyone “all tubes on these tables are going for $1 each today!”. After a couple of quick walkthroughs I realized that most of these were meant for the television market but I wasn’t going to let that get me down. As I was reading the numbers on the boxes I saw one I had not heard of before- the 6BL7GT.
I pulled out my phone for a quick internet search and came across the data sheet- perfect! It will run just like a 6SN7. I then noticed a link to a Head Fi forum thread and I followed it here. A quick scan left me with the impression that this was a good tube to have. Needless to say I grabbed everything he had!

After returning home I started going through these boxes checking the condition of each. The Zenith branded tubes were in great shape and as they were the tubes I had the most of I decided to try them first. Those who I’ve chatted with in the past know that I don’t use these in a tube head amp but rather a Lampizator TRP3 tube dac. Here they are in the Lampizator stacked on parallel adapters.

These tubes are AWESOME! I am really impressed with the sound quality these produce across the entire frequency range and I’m really baffled by the fact that these still seem to be one of those “under the radar” tubes. I haven’t had a chance to read the entire thread yet but am looking forward to catching more insight on these. Thanks to everyone who participates here as this has definitely led me to another great find!

 

[mordy]

@mordy / @gibosi
Thought I would jump in here with a quick post and story as this thread hasn’t seen much love lately. This last weekend I was at a swap meet here in the LA area seeing what I could dig up. There was a man there who had row after row of tubes- literally thousands. He walked out to meet those browsing the tables and would tell everyone “all tubes on these tables are going for $1 each today!”. After a couple of quick walkthroughs I realized that most of these were meant for the television market but I wasn’t going to let that get me down. As I was reading the numbers on the boxes I saw one I had not heard of before- the 6BL7GT.
I pulled out my phone for a quick internet search and came across the data sheet- perfect! It will run just like a 6SN7. I then noticed a link to a Head Fi forum thread and I followed it here. A quick scan left me with the impression that this was a good tube to have. Needless to say I grabbed everything he had!



After returning home I started going through these boxes checking the condition of each. The Zenith branded tubes were in great shape and as they were the tubes I had the most of I decided to try them first. Those who I’ve chatted with in the past know that I don’t use these in a tube head amp but rather a Lampizator TRP3 tube dac. Here they are in the Lampizator stacked on parallel adapters.



These tubes are AWESOME! I am really impressed with the sound quality these produce across the entire frequency range and I’m really baffled by the fact that these still seem to be one of those “under the radar” tubes. I haven’t had a chance to read the entire thread yet but am looking forward to catching more insight on these. Thanks to everyone who participates here as this has definitely led me to another great find!

The 6BL7 (and it's close sibling, the 6BX7) are great tubes that are underrated.
According to some, the Sylvania early 50s 6BL7 with parallel plates are the best sounding - possibly the Zenith tubes are Sylvanias with this construction. Most of these tubes have X plates and it is not so easy to find the parallel plates.

 

[LobalWarming]

The 6BL7 (and it's close sibling, the 6BX7) are great tubes that are underrated.
According to some, the Sylvania early 50s 6BL7 with parallel plates are the best sounding - possibly the Zenith tubes are Sylvanias with this construction. Most of these tubes have X plates and it is not so easy to find the parallel plates.

Agree. Altho I don't find my parallel plate 6BX7s much different that the X-plates.

However, some others (probably troublemakers like, @bcowen) claim that only GE (oh the horror!) made 6BX7/6BL7 during the 1950s. In the 60s, RCA, Tungsol and Sylvi began their own production. Sometimes finding the true origin of our thermionic treasures is like deciphering renaissance texts - by flickering incandescent light.

 

[mordy]

Agree. Altho I don't find my parallel plate 6BX7s much different that the X-plates.

However, some others (probably troublemakers like, @bcowen) claim that only GE (oh the horror!) made 6BX7/6BL7 during the 1950s. In the 60s, RCA, Tungsol and Sylvi began their own production. Sometimes finding the true origin of our thermionic treasures is like deciphering renaissance texts - by flickering incandescent light.

TBH I was referring to the 6BL7 about the parallel plates. I have several 6BX7 tubes under at least four different labels, but they are all made by GE - the sandblasted dots on the glass are the giveaway.

 

[Designsfx]

Having no experience with these I’m assuming “parallel plates” are the same as the “flat plates” mentioned on the first page of the thread. Of the batch I just purchased I ended up with-
Zenith, black parallel plates with triple micas x7
Sylvania, black x plates with triple micas x4
Tung Sol, black x plate x3
GE, black x plate x2
RCA, black x plates with triple micas x1

So now I just need to find mates for the last three so I have complete quads. The triple mica tubes are interesting- hope those weren’t some rare form of construction.

 

[mordy]

Having no experience with these I’m assuming “parallel plates” are the same as the “flat plates” mentioned on the first page of the thread. Of the batch I just purchased I ended up with-
Zenith, black parallel plates with triple micas x7
Sylvania, black x plates with triple micas x4
Tung Sol, black x plate x3
GE, black x plate x2
RCA, black x plates with triple micas x1

So now I just need to find mates for the last three so I have complete quads. The triple mica tubes are interesting- hope those weren’t some rare form of construction.

Parallel plates is the same as two separate flat plates. The Zenith tubes with the triple micas should be the right kind - check the numbers and codes on the bases and also a three digit code on the glass under the tube description.
Any tube with a number of white dots on the glass is made by GE.