How to identify Mullard ECC83 tubes?

[Axe_78th]

Greetings,

Can someone point me to a site that details mullard preamp tubes and how to identify them?

[thousandshirts]

This site may be of some use: http://www.audiotubes.com/mullcode.htm" onclick="window.open(this.href);return false;

I can only guess you're talking about real Mullards, not the recent New Sensor production with "Mullard" labels. The good old stuff can be confusing with all of the different labels (and re-labels, and sometimes re-re-labels!!) they put on them. But there should be a date code, and the site above should be able to help you with that.

Another little chart that might help: http://home.carolina.rr.com/billdougan/Bias.htm" onclick="window.open(this.href);return false;

If you have the Mullards in hand, you can always put them in an amp and fire them up to see if they are Mullards or not. A real Mullard preamp tube will give a bright flash when the amp is first turned on, then die down quickly to a normal glow. That doesn't narrow it down completely because some of the other Phillips tubes do that as well. But you should be able to see an "I61" or "I63" or something depressed into the glass.

There are lots of pictures and information available on the internet so if you're not sure yet, it's time to do some research before spending anything on these valuable tubes.

[Axe_78th]

This is the best place I've found to date. It helped me ID several tubes I had.

http://www.tubemonger.com/

[Axe_78th]

Another site that has looks of info,

http://www.tube-classics.de/indexen.htm

[Okiwaso]

I have a Mullard short plate 12AX7A here (Pics 1-4):
https://drive.google.com/folderview?id= ... sp=sharing" onclick="window.open(this.href);return false;

I also have a recently aquired Sylvania 12AX7A International tube that also says ECC83 Made in India and this tube looks identical to my short plate 12AX7A Mullard (pics 5-10)
https://drive.google.com/folderview?id= ... sp=sharing" onclick="window.open(this.href);return false;

This Sylvania also has BH stamped on it and QV stamped on it. From the Panasonic codes at the bottom of the link ( http://www.audiotubes.com/mullcode.htm" onclick="window.open(this.href);return false; ) that "thousandshirts" provided the B stands for Mullard and the V stands for Bharat Electronics India

So is this Sylvania actually a made in India Mullard short plate 12AX7A?


Thanks

[Jeff West]

Hello Okiwaso- Yes, the first is a Blackburn made Mullard, the second is Bharat Electronic Limited (BEL) made in Bangalore, India.

BEL had technical sharing agreements with Philips, who owned Mullard since 1928, but BEL was not owned by Philips, and BEL tubes are not "Mullards" (except on occasions when Philips bought them and sold them under Mullard brand).

If you look carefully, they don't look exactly identical. Two differences you'll find on those particular vintages are that the BEL there has the circular holes in the sides of the plates that go through to the "inside", whereas no Blackburn 12AX7 does. On the Mullard, if you look at the top mica as you face the plates, there are "skipped" points on the sides, characteristic of British Mullard short plate 12AX7s after late in the first year (1959), but not BELs or other Philips 12ax7s from the 1960s-70s. Various devils in the details can help the ID even when the codes are missing.

The BELs are fine 12AX7s, IMO, and of course the Mullards are true classics.

-Jeff