I'm not a big headphone user and have just an old ( repaired ) set of Superlux HD66B headphones . I saw this being talked about on another forum and decided to take a punt because it's really not a lot of money https://www.ebay.co.uk/itm/The-Bards...frcectupt=true
It has been lying on the shelf for a few weeks and I decided to give it a try over the last few days . Well , IMO it has made the headphones infinitely more listeneable with what seems like a bigger soundstage and a smoother sound .
I may even start using my headphones more Well worth a try at the price