Reporting to new chief executive Tom Wright, Ball will take up her post from March 1 in advance of the start date for the new charity a month later in April.
Ball will lead the development of the new brand for the organisation as well as devising and implementing an income generation strategy deploying its various databases and technologies.
Ball will also be responsible for the development of an offline and online marketing strategy.
Ball said: "Both heritage brands can boast of so much success down the years -- whether it be in terms of income generation, deploying up-to-the-minute marketing techniques or through engagement with the widest range of stakeholders to secure success.
"Our challenge is to build on that expertise and knowledge and make sure that the merged charity plays to its strengths and doesn't shy away from using the most innovative techniques and cross-selling opportunities at our disposal."
Wright said: "Amanda brings a uniquely strong track record of success to this important position in the new charity.
"The 'to-do' list is immense -- but I feel absolutely sure that under Amanda's leadership, the new charity can expect to see great things achieved very quickly indeed."