Disclaimer: This is an unsupported modification that may break your headphones or the amp! You do this at your own risk.
I don’t think I ever posted a proper picture of what I did:
Parts:
2x 2.54mm 2-pole pin Like this one
2x Vishay G200-series 220 Ohm (220 Ohm, glas covered wire-wound resistor, the important part is >3 W rating)
Cost: ~1€ or $1
I put a piece of heatshrink over the free leg. They are bent like this to prevent them making contact with anything in the amp.
This is them installed. As you can see, the 90° bend avoids hitting the transformer, the “off angle” one avoids the front circuit board.
You may rightfully ask yourself: WHY would you do this?
Simple answer: More power without all the noise, this is a speaker amp first, headphone amp second.
This mod (wich you can just unplug any time or replace with the supplied jumpers) lowers the output resistance to 110 Ohm (instead of 220 Ohm or ~0).