in 1926, an attempt at reviving interest in edison records was made by introducing a long-playing diamond disc which still rotated at 80 rpm but tripled the standard groove pitch to 450 threads per inch by using an ultra-fine groove, achieving a playing time of 24 minutes per 10-inch disc (12 on each side) and 40 minutes per 12-inch disc (these were the only 12-inch diamond discs ever sold to the public). a special reproducer and modified feed screw mechanism were required to play them. there were problems with skipping, groove wall breakdown, overall low volume (about 40% of that of the regular diamond discs), and a failure to exploit the format by releasing a limited number of discs. only 14 different edison long play discs were issued before they were discontinued.