[rellim68]

I have a vintage 4B circa 1989 with e frame transformer. When the amp & pre amp (hafler 915 ) are on, there is a very noticeable hum from the tweeters of my speakers.Would this be considered normal for this year of amp?I have tried non grounded plug end  on my preamp to check for ground loops, did not seem to help, I have disconnected my cd player to no avail. The amp was sent to bryston when I bought it, the muting relays were replaced as well as the power cord.Also there is a quite load pop when the amp is turned on.

question # 1- any ideas about the hum

question # 2 - any ideas about the pop when the amp is turned on.  

 I have read various posts but really did not find a clear answer


  Thanks J Miller

[antt]

I have a Vintage 1988 4b with e frame transformer (I bought it new, never had a reason to replace it).  The problems you describe have never occured in my amp.  I have had problems with ground loops, solved when I moved.  But the hum was not limited to the tweeters.  My amp also gives an audible "Pop" from each channel a few seconds after I switch it off.  There is no pop when I switch it on.  Sorry I can't answer any of your other questions, as I have no idea.

[James Tanner]

Hi,

Hum from the tweeter is very strange - it could be a bad capacitor?
The pop is the power transformers charging on turn on and discharging on shut - down. It is very normal with the older 4B's and will not cause any problems.

james