Noise Measurements on Pre-amp Valves

I was curious to see if there was any information on the net regarding the noise figures for any noise measurements on preamp valves
Noise is just one of the many things to look at in selecting a good valve for your amp and I thought it was worth taking a look at this.
Noise measurements on pre-amp valves  requires building some specialist test gear so I thought I do some research to find information.  I was particularly interested in ECC83 /12AX7 and see what is the lowest noise standard production valves and how they compare to earlier types.
I found this article by Tavish Design.( click here). Tavish design is a small business with a passion for designing high end very high quality valve based equipment for high end audio applications. They are located in New York.
If you open the link above, you will see a table of valves and their noise figures listed following testing.
First surprise is that NOS valves in general are shown to have the highest noise figures. The previous generation to the ECC83 is the octal based 6SL7 class of product and they seem to vary widely on noise but not to good either.
The noise figures are listed on the right hand side of the table and the first item on the list is a JFET transistor. Before you get worried, it is there just to show the difference between valves and transistors.  It is worth noting that transistors have much lower noise than valve. Significantly lower but we all know we prefer the valve sound !
For us folks interested in musical instrument amps , the ECC83/12AX7 is a key valve for us.  It usually sits at the front end of your amp and where your guitar is first amplified.  Any noise at the front of your amp is amplified all the way through the amp so you want the V1 position valve to be as quiet as it can be, but doing all the other things it needs to do.
I was surprised to see that the quietest valve was the JJ  5751 ( this is a lower gain ECC83/12AX7) and the JJ ECC83S was very very close behind.
The Shuguang f12AX7 rom China was very good.
My own observation is that the JJ ECC83S becomes more prone to microphonics over time in combo amps as compared to for example the Tung Sol 12AX7
So if noise is on your shopping list then I hope I have got you thinking. High power amps, above 50 watts  will benefit  from a low noise V1 valve than a smaller amp.
There is also all the sonics to take into account.  I recently wrote a blog on the different types of ECC83/12AX7 and you might want to have a look at that too. Click here to see the article 
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