14dBm is max input, so a hot modern DA output will overload the transformer. Verge of limiting is quoted as -24dBm with input all the way up, input has a 40 dB variable range. Input has both 150 and 600 ohm taps brought out to the connector, so that verge of limiting would translate closer to -30 dBm if you are using the 150 ohm taps. You could use whichever suitable H, U, O or T pad you prefer for either input. A 20dB pad is probably the right range for modern high level signals from a converter, though anything slightly lower wouldn't get into extreme compression easily. So 10dB could prove a better value in some instances. 15 dB; whatever suits the way you work.
Output already has a 0-20dB range 600 ohm T pad. It should also have a 620-680 ohm resistor across the output connector, as the output control expects a 600 ohm load to deliver the quoted dB steps. Maximum output with limiting disabled is quoted as 38.5dBm = 7W. Verge of limiting with output pad set set to 0 is roughly 30dBm = 1W. If you have 10dB limiting and turn the output down to -20, you should still be within the acceptable range of most AD converters, and not need an additional pad. If the knob position freaks you out, you might like an additional 600 ohm T pad between the output control and the output load resistor so the knob doesn't run so low, but that's all mental, the result is the same.
YMMV depending on how you like to run a BA-6, from barely touching to total slammed at all times.