I've only recently bought a CMoy amp to get a bit more volume out of a few things I have, but also with a view to making something similar. I ordered the amp with a second op amp to put in to try and educate my ears a bit, but then I also bought an LM4562NA on eBay from someone with 100% fb and who's been civil in email. I'd read a recommendation of it on this site during some random searching, and it was £4, new. Compared to the other two op amps when used with my Android tablet in the CMoy amp there is a horrible amount of squeaking and hissing when a browser is opened or a web page changes or a folder of music is opened. I can faintly hear this with one of the other op amps, I think it's an AD8066, but so faintly that it's not an issue and makes the 4562 seem a rogue chip to me. Should I expect noise like this? The only other time i've heard the same sound is with older IBM Thinkpad laptops, through headphones, when they've started to go bad, I think some item inside the screen lid i've forgotten the name of. I can't say I hear anything bad when used with my Sony Discman, but having a choice of three chips I wouldn't leave Mr Screechy in. The seller has said ot send it back for testing and that he'd replace it if need be. If it's normal though for that model, with a tablet it's no use so I'd ask for something else or a refund if he's willing in the instance of it being deemed non-faulty. I'd just like some rough idea as a layman and beginner in these things of whether wanting to get shot of this item is reasonable or whether its 'fault' is to be expected.