The HD598 has some graininess in the mids and highs that is ever-present indicating odd order harmonic distortion.

The HD428 isn't grainy, but has a bit of a smoothed over thickness or lushness in the mids and lacks articulation, indicating even-order harmonic distortion.

This was my worst nightmare about ordering something like this online

Unfortunately, the Amazon 'used return' monster came to me in my first delivery, so I am rolling the dice and re-ordering once the refund hits

Not much, but definitely more treble without sacrificing that sweet smoothness that is tube gear's utter lack of odd-order harmonic distortion

sound great too, either plugged into the receiver or piped thru my logitec PC system (their top o line with separate headphone amp)

For softer pop songs and guitars, "Acoustic" brings out the lighter more ethereal tones, but stay away from the flattening abomination called "Pop"; if you want a fun punchy pop song, I'd recommend "R&B", it may be a bit on the smooth side bass-wise, but it does the job well

For softer pop songs and guitars, "Acoustic" brings out the lighter more ethereal tones, but stay away from the flattening abomination called "Pop"; if you want a fun punchy pop song, I'd recommend "R&B", it may be a bit on the smooth side bass-wise, but it does the job well