They were aware that the House of Representatives was modeled to be sole aggregated voice of the people. The House is the totality of US democracic input.
And the senators were appointed by the state governors who were also democratically elected. The president was democratically elected via the electoral college. Justices are appointed by the president who was democratically elected and the senate who were appointed by democratically elected governors.
Again, to say the US is a republic and not a democracy is incorrect. It is both, just like a Civic can both be a car and an automobile.
Again, to say the US is a republic and not a democracy is incorrect. It is both, just like a Civic can both be a car and an automobile.