I have carried 2 turntables by hand from the United States to India on 2 different occasions. First instance was by Air India (I had about 40 LPs with me as well) and second instance was by Emirates. Had my laptop bag as well.
American airports do a baggage size check for hand luggage. If your luggage exceeds this size, you'll have to check it in. If you are carrying a receiver in its original packaging, your likely to fail this test and you'll have to check your luggage in. When checking in luggage, ensure that you use the original box (so that people know whats in it) and stick a large and clear label on the box, displaying your name (or some sidey will coolly pick it up on the conveyor on arrival, and say its his). Airlines are generally careful with electronics checked in. Some airlines follow the 1+1 rule which is, 1 checked in luggage stroller and 1 hand luggage bag. If this is the case, the airline may charge you a fee. Also keep a tab on the weight. There is a cap for checked in luggage and hand luggage. Hope this helps.