Hall, 74, sold his 41.6% stake in the club on Wednesday as Ashley stepped up his takeover bid.
"We've had quite a few people come to us, but many of them weren't right," Hall told BBC Radio Newcastle.
"I feel Ashley and his team are right. He'll take us to a new dimension. I'm certain he'll be good for the club or I wouldn't have sold to him."
Ashley purchased the Hall family's stake for £55m with the ultimate aim of clinching a complete £133.1m buy-out of chairman Freddy Shepherd and the remaining shareholders.
"We probably ran out of ideas a bit. There's no room for old men. I've got a lot of experience but it's a young man's game"
Sir John Hall
read>>> £55m buys billionaire a big stake in club's future
Newcastle United official club website
The Newcastle United stock reacts favorably on the LSE to the news.