CV4003, M8136 and 6189 are of the same family as ECC82 and 12AU7. CV4003 and M8136 were the codes commonly used by European manufacturers, such as Mullard and Brimar of Great Britain. 6189 seems to be an American code as I have a pair of 6189 made by Sylvania of United States.

Below are my last five pairs of tubes of this family series.

Mullard CV4003 / M8136 / 6189 (Big Shield Logo)

This can be considered as the best tube in my collection. A pair of Mullard tubes made in ’60. The tube was etched with the word “Mullard” inside of a big shield logo and word “M8136 Made in GT Britain”.  On its back, the tube glass was also etched with code  “6189 XA CV4003”.

Code 6189 is used for identification of a military spec tube and a premium industrial tube.

British Code CV (Common Valve) was said for replacing three sets of the old military used codes during Second World War. The three codes are:

• British Royal Air Force – V series, e.g. VCR, VU
• British Army – A series, e.g. ACR, AT
• British Royal Navy – N series, e.g. NC, NU

This tube delivers very rich mid range with full detail. It sounds also much luscious and creamy than the other Mullard tubes in my collection.  My opinion, it is surely an excellent and all round tube highly recommended for use.

Mullard M8136 (Big Shield Logo)

This is another pair of Mullard that it looks alike with the 6189 tube introduced above.

The tube body was also etched with a big shield logo word “M8136 Made in GT Britain” , except for its back does not have the code   “6189 XA CV4003”.

I am not too sure on when it was manufactured. It sounds quite close to the 6189. For the reason, I continue with the 6189, the best one for my amp.

Mullard M8136 (Small Shield Logo)

This tube looks alike with the M8136 above except that it has a smaller shield logo than the one above. Mullard tubes of small shield logo were said for manufacturing in ’70.

This M8136 still has an identity of Mullard sound of rich mid range, but is interior to his elder brother of M8136 big shield logo in terms of musicality and smoothness.  

Mullard CV4003

A pair of Mullard CV4003 has no shield logo at all. The tube body was etched with code “000 4003 CV4003 KQDD/K 81-27”.

It seems that 81-27 was a date code for the tube production.

If this assumption is correct, Mullard manufactured this tube at its latest production stage. 

Sylvania JAN 6189W

As mentioned earlier, 6189 can be both a military spec tube and a premium industrial tube.

My opinion is, this classic American tube has similar sound quality to Philips JAN tube, which delivers fast, clean and detailed sharp soundstage but does not have the warm and rich mid range sweeties, like the Mullard always does.     

When time allowed, in next articles I shall continue with my collection of audio tube series 12AX7, 5751, ECC83, CV4004 and M8137 that are of the same family for use in pre-amp.  See you!