I had this item with little use for awhile. When used with Audio Technica MTH50's and VModa LP's I had a crackle and pop. Sent JDS Labs an email and the president got back to me the next day. He had me send it to him for the solution. This company tunes this amp to your specific headphones. Mine didn't match the generic unit they sell here. I recommend dealing directly with JDSLabs.com to get right setup. The result of their tune is OUTSTANDING!!! Thanks John at JDSLabs