[Old Punk Git]

Wonder if anyone out there can help me? I have been used to separates hifi up to now but for reasons of space am now using the above micro system instead. Using a recently bought pair of Sennheiser HD555's thru them sound is generally excellent BUT at highish volumes (espec with tone settings on) the headphones omit a loudish crackling sound in either or both earpieces. Turning off the tone settings helps and obviously I would normally listen at more tolerable levels anyway but irritating me so can anyone advise is it probably just a deficiency of the headphone output on the Denon as opposed to the phones as I really like the sound they produce. Thinking of digging out the old Cyrus gear anyway so this may become academic but any thoughts/advice appreciated. Ta.