Krell Evolution Pre and Power Amps Service advice

[sidlal]

Hi, I have been using Krell Evolution 302 power amp and Krell Evolution 222 preamp since Dec 2009. Over the last couple of months, I have noticed a very faint hiss coming through the tweeters when I put my ear close to them, but not from my seating position. Additionally, when the system is powered on from the mains, there is a low ‘bum’ sound through the speaker each time I change the input on the 222 preamp, which I can hear from my seating position. This ‘bum’ sound stops after about 2 minutes of the equipment switching on. The volume of the hiss or ‘bum’ sound do not change when the preamp volume is changed and also appear when it is turned down fully or on mute.

The pre and power amps have never been serviced since purchase. Any advice on what the problem may be and whether there is any high quality service provider in the Delhi-NCR region who can possibly fix this? Thanks!

 

[oldmonk]

Check if all equipment is properly earthed

Normally electric linesman use a bulb to certify....do go beyond that and engage someone who knows his stuff.

Sometimes load variations on the main power line can cause humming sound

The humming sound from my speakers vanished when I connected the body of my CDP to the ground pin of my amplifier

But before you do that please be careful and engage a professional .

The hiss can be ignored since it doesn't show up near your seating position....imo

There are folks in this forum who can fine tune and add value to my suggestion

Good luck !