1095 Hum

[KEN KAZ]

ok, i periodically have the 1095 hum.

it seem sthat when the unit is cold there is no hum. whenyou get it nice and toasty warm, like after listning to Zeppelin at 100dB for an hour or so, i can hear a hum. it is a 60hz hum that rides on top of the slight ringing in my ears.

i have satalite tv, not cable, I know that is a culprit for a lot of folks.

do othes have this? or are others' hums constant?

the unit is 9 months old, i had the hum when i got it, an di used a cheater plug till this weekend and i had some time to kill, so i tried to de-bug that problem.

thanks
kaz

[mitch57]

Is the hum coming from the speakers or from the amplifier?

[csuzor]

If the hum is from the amp, I suggest you try to ground the chassis. What is a cheater plug? I made a plug with just 1 copper wire connected to ground, and a round lug on the other end that I connected to the chassis using 1 of the chassis screws. It prevents the hum, which I believe is due to grounding issues, and made the whole HiFi "touch friendly", no more electric discharge when touching it.

[RebelMan]

Intresting csuzor. Any chance you upload a pic of that? Your implementation is a novel idea and one I think I might adopt. We have pre-made cheater plugs here in the States but I don't believe they offer any way to ground them to the chassis for safety.

[bigburner]

RebelMan, is a cheater plug a normal power plug with the earth pin cut off?

csuzor, isn't the amp's chassis already connected to earth via the earth pin on the power plug?

[csuzor]

csuzor, isn't the amp's chassis already connected to earth via the earth pin on the power plug?

No, Rotel have (for reasons that only they know and we can only speculate on) ommitted the earth pin on the back of their units, so neither amp nor preamps are earthed.
I'll post a photo, but it really is very simple. When I occasionally remove it, within a few minutes there is electric build-up, and touching either preamp or amp gives me small electric discharges, which are non-existent when the earth plug is used.

[soundhound]

The ground loop which is spoken of probably is not what kaz is up against. His sounds thermally related. As we all know ground loops in their simplest of forms are when one component pulls ground thru another component, rather than having it's own.

[RebelMan]

No, Rotel have (for reasons that only they know and we can only speculate on) ommitted the earth pin on the back of their units, so neither amp nor preamps are earthed.

This is only partially true. The RB-1080 does have a third grounding (earthed) pin. Some Rotel source components and pre/pro's are built without them, I believe, because they don't draw large amounts of current and perhaps they feel a "polarized" plug is sufficient enough for grounding purposes. The positive side effect of such a plug is reduced/eliminated hum normally caused by the 60Hz ripple. OTOH as csuzor points out, static build up can occur on the component and send shocks to your fingers. Ouch.

[RebelMan]

RebelMan, is a cheater plug a normal power plug with the earth pin cut off?

More or less, yes. It is actually an adapter that converts a three prong plug into a two prong one. The problem with a cheater plug is that it is not "polarized" either and so there is no route for ground except through your component and eventually you when you make physical contact. I was curious as to how csuzor was circumventing this and by establishing a path to ground that is safe and doesn't incurr the 60Hz ripple.

[lvhung]

many problem with Rotel
but still many buy Rotel
Rotel is only choice at 2-3 K