The 12AU6 is the equivalent version with a 12 V heater.
The 6AU6A is an improved version for equipment with series-connected heaters that ha controlled warm-up and heater-to-cathode voltage rating increased to 200 V. The 6AU6WA is a ruggedized version.
Tek part number:
- 157-0073-00 (selected pair)
- 157-0059-00 (6AU6A)
- 154-0284-00 (6AU6WA)