a DIY one i made with premium parts , sure messed up the sound. Thought adding 10 ohm in parralel will help as the load imp. is reduced, but it didnt. Maybe the resistor in parallel reduced the current through the HE6. But in all the sound was worse than direct connection (to speaker posts)
For tube amps adapter is a necessity, but i wont put he-adapter in , unless i have a 300w+ amp.