Tube nomenclature

[butchbass]

What would the difference in a 12AT7 and a 12AT7WA be? 

 

[Paul Birkeland]

The "W" traditionally indicates some additional testing in accordance with military specifications.

The "A" indicates a controlled heater warmup characteristic.

Neither of these are appreciable differences. 

 

[Grainger49]

They are drop in replacements, the "WA" is possibly better sounding for Paul's reasons.

 

[butchbass]

Thanks for the info. Music enjoyment is the best part of this hobby but the eduction also brings fulfillment.