Baxendal circuit output impedance

Kits Audio Hi Fi Projects
1

I’ve completed your K8084 preamplifier-tone control
I’d like to know the output impedance, not specified. What part do R5,6 (10K ) play in it?

2

Output resistance can be considered as more or less equal to series resistor R5/R6.

3

Thank you.
I can therefore use headphones if their impedance is high?.
Could/should I reduce R5,6 for better output on low impedance phones such as 8 ohms?

4

Should work with high impedance headphones.

Check max. volume with low impedance phones.
If too low, reduce value of resistors.