Back in the days of octal bases, the best double triodes were, 12SN7, 12SL7 and Mullard's wonderful ECC32, ECC33 range of valves were all the go and were the ones that everybody used. At the onset  of things becoming smaller (this trend still continues in electronics today), the B9A based valves were becoming very popular. Thanks are due again to our Netherlands friends in the Dutch firm, Philips Gloeilampenfabrieken N.V. based in Eindhoven; to the best of my knowledge, these guys developed the ECC81/2/3 range of double triodes as well as the EL34 and EL84. 

The development of the ECC81/2/3 double triodes was a major leap forward in the history of valves. All three of the variants in one way or another have been used in almost every piece of valve electronic equipment of all kinds, be it Hi-Fi amplifiers, guitar amplifiers, TV's, radio ham/transmitter equipment, radios, tape recorders, organs..... and the list goes on!? Open any of these pieces of equipment and you would be hard pressed not to find one of the ECC8's? range in there:

ECC82's were used in almost every valve TV worldwide!! What a star it is! 

ECC83's have been used in virtually every Hi-Fi/guitar amplifier ever produced too, making it 2nd behind the ECC82. 

ECC81's however were less used throughout though they almost always do tend to be be the phase inverter in almost every guitar amplifier of which uses four output valves as the ECC81 has better drive characteristics for this purpose.

 

The old octal-based range, like the 12SN7, 12SL7, ECC32 and ECC33, had the following amplification factors respectively: 20, 70, 32, 35. whereas the ECC81/2/3 range of valves have amplification factors respectively as follows: 60, 17, 100.

 

The 3 variants of the ECC81/2/3 range of valves are also known worldwide again respectively as 12AT7/12AU7/12AX7, and are almost always marked with both numbers.

 

Many of the currant valve (tube) manufacturers of today are not only reproducing the whole range of ECC8?'s (including the older octal ranges), but also are doing many supposed up-rated better variants of them all! There is a lot of these variants out there and yet there is still a high demand for the original production versions of these classic valves. I wonder why!? Is it because, as in almost all cases, the originals are the best!!?? I'm sure it is. Come on Mullard........... Why don't you jump on the current valve (tube) boom bandwagon, restart the good old British company, and give us all your super valves again!! 

 

- John Chambers.