The Reference 6J5 Thread (L63, 6C5, 12J5, 6P5, etc.)

[WildPhydeaux]

Nice find with the boxes displaying the signal corp contract number SC961A! Are the tubes also stamped with that mark?

To my understanding that would be month (top) and year. Oddly KenRad used both A-L and M-Z for the month but I've never read a plausible reason why. Note that neither O or Q are used. Perhaps the M-Z was used after GE purchased Kentucky Radio's tube division in the mid-40's? Dunno.

So I would say those are November 1944.

Cheers,
Robert

 

[shwnwllms]

I've never read a plausible reason why. Note that neither O or Q are used.

Just a guess, but they may have omitted them as they were too close from a font standpoint and could be mistaken for each other (esp when markings fade over time)

 

[WildPhydeaux]

Just a guess, but they may have omitted them as they were too close from a font standpoint and could be mistaken for each other (esp when markings fade over time)

Very droll, dude, nice work.

Cheers,
Robert

 

[Designsfx]

Nice find with the boxes displaying the signal corp contract number SC961A! Are the tubes also stamped with that mark?

To my understanding that would be month (top) and year. Oddly KenRad used both A-L and M-Z for the month but I've never read a plausible reason why. Note that neither O or Q are used. Perhaps the M-Z was used after GE purchased Kentucky Radio's tube division in the mid-40's? Dunno.

So I would say those are November 1944.

Cheers,
Robert

I considered the post GE production but I believe at that point they would have included EIA codes as well. The only markings on these tubes are the brand name and the K/3. I figured 1943 for the year and added one two week period for each letter which brought me to the end of May. I did not consider two month periods for each letter- not that savvy when it comes to the art of deciphering date codes. I haven’t checked the second quad yet- they may be the same as the seller claimed to have 80 or so tubes all from the same box.

 

[mordy]

I considered the post GE production but I believe at that point they would have included EIA codes as well. The only markings on these tubes are the brand name and the K/3. I figured 1943 for the year and added one two week period for each letter which brought me to the end of May. I did not consider two month periods for each letter- not that savvy when it comes to the art of deciphering date codes. I haven’t checked the second quad yet- they may be the same as the seller claimed to have 80 or so tubes all from the same box.

My guess is that each letter represents a month, skipping I which could be read as a 1. That leaves K = October. Sometimes the alphabet sequence started with N and omitted Q and W: Q could be mistaken for O and W was used in tube designations.
But different manufacturers used different systems in different time periods; therefore you have to know who the manufacturer was as well.

 

[Designsfx]

So a two year period for the alphabet? (or close).. I think I read something similar in one of the RCA dating schemes along those lines

 

[jonchard]

I bought the Mullard white print version of these and used with Elrog TM.
I was so underwhelmed with these that I sold them at a loss just to get rid of them. I have a hard time believing there is a huge difference between the white and red version but I didn't want to hunt for another quad. I tried a Russian version (?) and also sold those and the adapters!

I trust your ears @shwnwllms but these were not a driver tube for me! Thankfully they were cheap enough to try the experiment.

I absolutely adore the whiteprints and the Russian 6C5C (both 60's and 70's). I just dont hear them lacking in any way. Whereas most others i listen to are missing in many areas. Maybe we have different synergies with different systems. What are your favourite drivers? What do they bring to the party that others dont? I have a very eclectic and varied taste, but would not really listen to classical or chamber music. I guess different drivers will synergise with different amps and designs. It almost seems a fools errand to chase another persons favourite.

 

[mordy]

So a two year period for the alphabet? (or close).. I think I read something similar in one of the RCA dating schemes along those lines

No- the alphabetical sequence only covers one year but sometimes a manufacturer uses A as a starting point and sometimes N as a starting point.

 

[mordy]

I absolutely adore the whiteprints and the Russian 6C5C (both 60's and 70's). I just dont hear them lacking in any way. Whereas most others i listen to are missing in many areas. Maybe we have different synergies with different systems. What are your favourite drivers? What do they bring to the party that others dont? I have a very eclectic and varied taste, but would not really listen to classical or chamber music. I guess different drivers will synergise with different amps and designs. It almost seems a fools errand to chase another persons favourite.

MIt almost seems a fools errand to chase another persons favourite.

You are right in that the same tube may sound different in different amps.
However, some tubes sound very good in almost any amp.
To me that is a reason to pick up on someone’s favorite tube. However, it helps if you know that person’s taste in sound and how it aligns with your taste.
Even though people hear things differently and have different tastes in music and different equipment, in my personal experience, it is quite possible to rely on the recommendations of certain people who hear things the same way you do.
In the beginning of my tube equipment journey I did not think that it was possible given all the above mentioned variables, but experience has borne out that it is quite possible.

 

[Designsfx]

No- the alphabetical sequence only covers one year but sometimes a manufacturer uses A as a starting point and sometimes N as a starting point.

So basically a 50% (actually much less) chance that you’d ever guess a correct date across any given decade! Someone was really overthinking that concept!

 

[WildPhydeaux]

Back in the day nobody cared in the slightest about the year, nevermind the month and would assume we have all taken leave of our senses. They're mostly there for production reasons, being able to track issues months down the road, not years.

Cheers,
Robert

 

[Designsfx]

Infinite numbers and combinations there of- if only they would have had bar/QR codes we could get down to some serious bragging on tube dating.

 

[mordy]

So basically a 50% (actually much less) chance that you’d ever guess a correct date across any given decade! Someone was really overthinking that concept!

You can educate your guesses lol - by looking up the tube on Radiomuseum you can see when it was first produced. As an example, if the tube was first made in the 60's, you can cut out earlier decades and you only have to choose between the 60's and the 70's. If you have the original box it can often give clues to the decade since most boxes changed design over the years. Likewise, the coding system and print on the tubes changed and all this helps to identify the decade.

 

[mordy]

Back in the day nobody cared in the slightest about the year, nevermind the month and would assume we have all taken leave of our senses. They're mostly there for production reasons, being able to track issues months down the road, not years.

Cheers,
Robert

I think that it is safe to say that very often older NOS tubes sound better but not always. Since tubes are getting more scarce you often can only buy one at a time and you need that information to make pairs that more or less match each other.

 

[WildPhydeaux]

Infinite numbers and combinations there of- if only they would have had bar/QR codes we could get down to some serious bragging on tube dating.

The scanners required to use those codes would require vacuum tubes. And their accuracy would depend on brand, construction, era, circuit design, physical location of where the scanning was done, angle at which the scanner was held, cleanliness of the power supply and the dexterity of the person holding the scanner. So they went another direction.

Cheers,
Robert