Rays Tubes

Whoops! I just googled Billington out of my own curiosity.  To my surprise, the business is still in operation. I don't know whether their Chinese made 12AT7 (which went by another alphanumeric designation, as I recall) is still available.

My Atmasphere monoblocks originally used 12AT7s as input tubes, which means they were responsible for most of the voltage gain across the whole circuit. At that time, I purchased a wide variety of different brands of 12AT7, to determine which sounded the best. The first finding is that it made a considerable difference; different 12AT7s sounded different. The surprising finding is that a Chinese variant sounded the best.  In those days, there was a tube vendor operating in the UK called "Billington". Their top of the line 12AT7 was called "Billington Gold", made in China.  I compared it to Mullard, GE, Sylvania, and some other NOS types. Billington Gold were the best sounding by far. The bad news is that they had a short life span in the amplifier circuit.  This saga played out in the late 90s or early 2000s. I think Billington the vendor is no more.

In many cases, in phono stages, 12AU7 is used at the output, as a cathode follower. The CF is needed to reduce output impedance, so the stage can drive a linestage or amplifier. The CF adds no voltage gain, so the choice of brand or provenance is relatively inconsequential. Same applies to an amplifier where a 12AU7 may be used as a phase splitter. In a linestage, 12AU7 may add signal gain, and there it may pay to use a select tube. But just remember that tubes age and over time that wonderfulness you think you hear may fade. Real Amperex Bugleboys are the best 12AU7s I’ve heard, but 12 or 6FQ7s were better.

Carpathian, it’s really not that hard to understand the differences among tubes, if you read some basic texts on the subject. Of course before substituting one type for another you need to understand how to read the data sheets.

The carpathian, yes, 12AU7 and 6 or 12v FQ7 are interchangeable, but you have to choose the version of FQ7 that matches the available filament voltage. Same specs for all other parameters, more or less.

Any 6FQ7 or 12FQ7 (depending upon the available filament voltage) will out perform any 12AU7, and they’re cheap.