Vintage Mullard and Magnavox tubes

[Bigsby_fab]

Looking to identify those 2 vintage tubes:

_ one being a long plates Mullard ECC83/ 12Ax7 Made in Great Britain.
_ one being that Made in Japan yellow lettering long plates Magnavox 12AX7A.

I am no expert in identifying vintage tubes, but would like to know more about these, date of production, specs etc…
Seeking help from the experts on the subject, any help would be greatly appreciated.

Thanks a lot

 

[Wally]

No expert here….but
There should be a code on the tube with the Mullard logo on it.
It will be etched and be more durable than the rest of the markings on the tube. The two lines of these codes will be on the bottom third of that tube. The top line will have three letter&numbers. The bottom line will have three or four….prior to 1960 there were three on the bottom line. In the ‘60s and ‘70s there were four. If that code is not there, it was not made in England by Mullard.
Magnavox??? My guess it is from the 1970s?? Maybe the late ‘60s.

 

[Wally]

One might think that four digit number on the Magnavox is a date code….17th week of 1969??? Are those the numbers…6917?
Do you see those two lines of codes on the ‘Mullard’?

 

[Bigsby_fab]

One might think that four digit number on the Magnavox is a date code….17th week of 1969??? Are those the numbers…6917?
Do you see those two lines of codes on the ‘Mullard’?

 

[Bigsby_fab]

Thanks Wally!
Bottom third of the Mullard seems to read
F91
B8B
Then top third says 128

 

[Bigsby_fab]

(link removed)

 

[Wally]

MULLARD VALVE ETCHED CODES - HOW TO INTERPRET THEM

There is much conflicting fokelore on the internet about the Mullard etched valve codes so I thought I would add our two penny-worth. The etched codes have value to us today as they contain two discrete nuggets of information; firstly, should a valve loose it's printing you can identify the...

mullard.org

F91 is a type of ECC 83/12AX7 it seems.
B8B is Blackburn, 1958, February.

I don’t know what the 128 at the top is…but it is not part of the etched
markings that establish what Mullard tube and where it was made.

 

[Bigsby_fab]

One might think that four digit number on the Magnavox is a date code….17th week of 1969??? Are those the numbers…6917?
Do you see those two lines of codes on the ‘Mullard’?

Ok from Ampgarage.com it says:

F91 Long Plate Dual Halo Getter: Similar in sonic characteristics to the MC1 Mullard above. This version comes from the late 50's (roughly 1957-1958) and will sometimes come with a square getter. It sounds very similar or the same to the MC1 Mullard, but is usually a bit less expensive. You can tell this type by the etched F91 code on the bottom of the glass, along with the 'B' Blackburn Code + a Number and a Letter.


MC1 Long Plate Square Getter: The most sought after, early production and expensive Mullard ECC83 from the mid-1950s. This one has 17mm long gray ladder plates and a dual supported square getter. This is the ultimate 'Mullard' sound.... big, open and warm with a tweedy harmonic overdrive. The etched MC1 code on the bottom of the glass denotes this type, along with the 'B' Blackburn Code + a Number and a Letter.

So date around ‘57/‘58

Guide to NOS and Vintage Audio Tubes - The Amp Garage

 

[dan40]

That 58, longplate Mullard is a highly sought after tube. Hopefully it still has plenty of life and is not microphonic.

 

[Wally]

There you go. The WWW is full of info. When you put it in an amp, you will know what that individual tube does…..

 

[Bigsby_fab]

That 58, longplate Mullard is a highly sought after tube. Hopefully it still has plenty of life and is not microphonic.

I just put it in my Vox AC30 in V1.
it sounds beautiful, with a lot of details and harmonics, very open sounding, sustain is excellent and this highs are smooth.
The mids have a “woody” quality if that makes sense, I love it!

 

[Wally]

No microphony?

 

[Bigsby_fab]

No microphony?

No microphony and very quiet, no hiss!

 

[Vibroluxer]

A real Mullard 12a*7 will flash when the power is turned on. No other preamp tube does this, only vintage Mullards.

 

[Engine Swap]

Amperex 12AX7 tubes also flash

 

[Bigsby_fab]

Now, a question I have is about the Magnavox (Japan) 12ax7a, would it handle being in a cathode follower spot?

 

[Wally]

Now, a question I have is about the Magnavox (Japan) 12ax7a, would it handle being in a cathode follower spot?

Being a 12AX7/ECC83, it should. If not, it is a compromised tube.

 

[tubedude]

Amperex 12AX7 tubes also flash

Many sold under that name were actually Mullards. They'll have the Blackburn code on them.

 

[fretknot]

A real Mullard 12a*7 will flash when the power is turned on. No other preamp tube does this, only vintage Mullards.

Tungsram will also flash.

 

[abcdefghijklmnop]

I just bought this 1956 Mullard yesterday for $6.50 out of a lot of NOS tubes, from a local electronics store. It tested good on their tube tester there. It gives the little "chirp" flash when installed and the amp is turned on, but alas it is dead with no output. Its too bad.... what could have been. RIP.