Hey Doug,

Whilst I don't know the maths of it yet, my ears tell me the opposite. I've got two other units here with a 25/50us switch on the back, and changing them to the lower position definitely boosts the treble.

Although the general concept of pre & de-emphasis makes sense to me, I'd welcome an explanation of the 'f3' frequencies that John C mentions. Can anyone educate me, or recommend a publication on the subject? Everything I've found on the internet so far is way too general.

Thanks & Regards, Steve C