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Sunday, January 16, 2022

Tube of the Month : The 6AW8A

 Hi!

Over the years I kept buying tubes which I found interesting based on their tube data but which are completely unknown in the audio world. One of these is the 6AW8A.



The 6AW8A has a triode and a pentode section. The triode section caught my attention due to the technical parameters which seemed interesting for audio use.


The 6AW8A is a 9 pin miniature tube. The pinout is shown on the left. It has a 6,3V heater which needs 0,6A. It is suitable for series connected heating in a 600mA heater string as well as parallel heating. There is also a version called 8AW8A which has a 8,4V/450mA heater. The 6AW8A has a high mu triode section and a sharp cut off pentode. The characteristics of the triode section are quite interesting. It has a high amplification factor of 70, similar to that of a 6SL7 but at a much lower plate resistance of only 17500 Ohms.  That's what made me buy a bunch of 6AW8A and put them into the box 'interesting tubes to be checked for use in audio later'. Well the check later turned out to be more than 20 years now while the 6AW8A had been lingering in tube drawers. I don't know if I well ever get to actually use the 6AW8A in a project but at last I pulled it out for a closer look and a tube of the month post. For the complete technical specs see the General Electric data sheet. As always let's have a look at the plate curves, starting with the triode section:



And here the curves taken with a tracer:



The pentode section:




The pentode triode wired:



A very interesting tube indeed and definitely deserves more attention.



Here we have a General Electric 6AW8A.






Tung-Sol:








Here the three grids of the pentode are nicely visible:





Sylvania 6AW8A:








A very interesting tube. Both sections should be well useable for audio. Maybe a phono stage?

Best regards

Thomas













3 comments:

  1. Entry-level SET amp? Triode for gain stage and pentode-wired-as-triode to drive a DHT (10y, 2A3, …)

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  2. Hi Mr. Mayer, what is the scale do you use on the tracer? Triode curves for the pentode are usefull. Where do you connect screen for triode measurements? Thanks!! Love your work.

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    Replies
    1. Sorry forgot to note the scale when I took that trace. Screen is connected to plate

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