Grado makes a very good adapter cable for quarter inch plug to eighth inch plug for headphones. But, going from an eighth inch to a quarter inch seems more tricky to me. The cheap plug adapters out there seem to be hit or miss to me. I recently received three custom made cables that have an eighth inch jack (female) with a quarter inch plug (male) with eight inches of cable in between. These aren't much better. The problem appears to me to be the eighth inch female connection for both cables and one piece plug adapters.