Dating from 1955 to 1990, it is a library of virtually every UK and US top 40 record in that period. While the majority are singles - 15,000 of them - there are also 5,000 albums, many rare.
Mr Gambaccini, who also presents the Radio 4 arts show Kaleidoscope, began buying records as a teenager. But his youthful enthusiasm was dampened by his father who forbade him - mistakenly as it turned out - from buying singles because they were a waste of money.
It was not until Mr Gambaccini left home that he could indulge his passion, and he bought a lot of his early records from a shop in Times Square, New York, which sold old juke box singles.
"That way I could quickly get to accumulate the hits of the Sixties that my father didn't allow me to buy," he said yesterday. "He forbade me from buying singles because he thought that singles were an example of planned obsolescence."
Ironically, Mr Gambaccini is one of the few who could make big money from his collection, which would be worth at least pounds 80,000 if broken up. As it is being sold by Sotheby's in one lot, it is estimated at a much lower pounds 15,000 to pounds 20,000.
The DJ began collecting seriously when he worked in college radio when studying history at Dartmouth College, New Hampshire, and then while reading PPE at Oxford.
During his career, which has included stints on Radio 1 and Classic FM, he has been sent thousands of records but he was always a "fanatic" and was unable to stop buying his own.
Mr Gambaccini kept his records and CDs on floor-to-ceiling shelves in a bedroom in his north London house.
He made the decision to sell when he filled his last CD shelf - he couldn't bear to give up another room. "My record room had become all records and no room," he said. "Something had to go and I thought it should be the vinyl. I can't use it any longer in radio stations because they have all gone to CD."
Among his favourites to be sold are James Brown's anti-drugs public service announcements of the Sixties, the Stax Stay In School album and Motown stars such as Marvin Gaye sending greetings to the Motown Appreciation Society. The sale is on September 18.Reuse content