Rotel RB980BX power amp hum and "pop"

[metako]

Erm ---- Will you ever be happy though. I suspected as much (that it's normal) but it's no excuse.
A good relay will not audibly affect the quality, if you want proof of this just wire the relay into the speaker leads and energise it with a battery.
Good to know it's not faulty as such though.

I guess it wont hurt to try. Email sent Nordic.

 

[Mooly]

Hi Metako, the guy is talking through his ****....

I take it you mean Mr Rotel and not Mr Mooly.
If it appeared I was refering to offset protection I am not. Just saying prove to yourself that a series relay won't interefere with sound.

 

[Nordic]

I would never insult a cow like that...

 

[Mooly]

Hello Nordic, I edited it as you posted

 

[Nordic]

Some people do say there is an audiable contribution from relays.... It has never struck me as obvious enough to investigate further...

Then again some people believe in sonic rocks etc....

 

[metako]

well just as a very belated postscript to this thing...

I just finished seperating my Pioneer A400 integrated into pre-power and plugged the Rotel power amp into the A400 pre section and lo and behold all the thumping has disappeared! Its crystal silent on turn on and switch off,, even with the A400 pre left powered up. I cant explain it but its beautiful. The pre section of the Tandy amp must not have been compatible to the Rotel or maybe the A400 has something in it that suppresses turn on thump. Whatever-its blissful and now I can plug my tweeters back in!

(and I never did recieve that circuit Nordic)

 

[Incloud]

Well I can hardly believe it but the hum is 99.9% gone!!! I turned the amp upside down and looked carefully at all the casework screws on the bottom. One screw was loose but I thought nothing of it and removed all the screws and removed the base cover.

Everything seemed OK and I noticed that the loose screw went into a metal "riser" or spacer coming out of the PCB. There are 3 of these spacers but only 2 had screws going into them from the case, and one of those was loose. The 3rd spacer comes out in between a couple of the ventilation slots in the bottom cover and looks like it has never had a screw in there (no screwhead marks) and doesnt even properly line up.

Could these little screws to the risers be critical? I replaced the cover and screwed all the screws down tight, connected the speakers up again and bingo! the hum was much much fainter! I was amazed at the function of those little screws! Then I plugged in the interconnect of the preamp (still switched off) and the hum became even quieter, so much so that I have to strain with my ear very very close to the speaker and I can JUST still hear it. I can live with that. Maybe if I put a screw in the 3rd spacer the hum will disappear completely!

This has been a very strange experience. I have never known a small screw through the casework to be so critical. These Rotel amps are weird.

Thanks very much for your ideas Alex and Jorge - you were both in the right ballpark - it was something loose Jorge and was to do with the casework Alex.

The switch off pop is still a nuisance - it is so loud sometimes that I'm sure it will blow my tweeters soon. Will switch off at the wall switch till I find a solution.

I am completely new here and just happened across this thread. I just got a Rotel RB-956ax and it also is making that humming noise and a hurtful POP when turning on and off. I'll probably have to deal with the POP because eveything you guys are saying on here is way over my head. As far as the humming or ground loop, I have to leave the gain turned way down and crank my receiver levels to max in order to eliminate the hum or buzz. I am at my wits end with it. The Rotel sounds absolutely amazing with my system. I am completely shocked how much of a difference adding an amp has made. Hopefully I can manage to get this working without the annoying buzz / hum as I could not go back to the dull sound I had before. As asked earlier on, will the POP we hear damage the speakers? Is there a way of using a power strip or line conditioner of sorts to atleast be able to turn the amp on and off without damaging something? Seems like an incredibly poor design if it has to make that sound. Thanks in advance for any support on this subject.