Oliver invested in the company when it had cash flow difficulties four years ago, but payment has now been completed as agreed.
Hamilton-Smith said: 'We weren't in good shape back then. We needed to find someone that was prepared to step in because we were confident of our long-term future, but had immediate problems.'
The deal will make Hamilton Smith the majority shareholder with 90% of the company. He told Broadcast that it will be signed within the week.
Hamilton-Smith is giving Oliver 10% of the company's shares out of gratitude for his help. 'He did everything he said he would, which is almost unheard of these days. I couldn't have had a better sleeping partner,' Hamilton-Smith said.
China Blue has worked on the Escape from? series and Secrets of World War II - both for Five. Earlier this year the company invested £250,000 in a 5.1 HD audio suite.
Hamilton-Smith took over as chairman of the Association of Professional Recording Services (APRS) a month ago and chaired his first session on Monday (29 November). He said 'he was very positive' about the association's plans.