hum and noise - help

[Dougie Fresh]

Using a Rotle 5 channel amp for only 2 speakers (plan on hooking up 2 more later on).

Getting a hum/noise with 3 channels open, is that the problem?

The pre-amp is Rotel only have the bare minimum of wires hooked up and only one source.....don't know why there is a hum?

Any ideas/help?


[This amp was hooked up for a couple of years to a 5.1, I don't think there was a hum]

[Kevin D]

What one source? Is the pre-amp connected to a TV as well?

Kevin D.

[Dougie Fresh]

Thanks KD,

Disconnected everything I could to see where this is coming from.

What's left is shown here, all RCA except for the HDMI to TV.

I've had all this gear for a while and all worked fine, very quiet (but never in this combination).

Now I'm getting a 60cycle hum.

[Dougie Fresh]

Okay - the plot thickens.
The hum is back as soon as any rca goes in the pre-amp - any and all inputs.
Something thru the ground?

The volume knob is all the way down - btw

[Dougie Fresh]

Trying different strategies - replaced amp, now a pair of BX980's - whisper quiet.

The Pre-amp and the heavy 5 channel was just not compatible.

Maybe I can hunt down a different pre-amp and/or get the 5 channel checked out, but I think it was fine the last time it was used in the 5.2 HT.

[wkhanna]

Did you try grounding the chassis of the Pre & amp?
It sounds as though one of the units may be at a different potential.
Are all the units on the same circuit?

[Dougie Fresh]

Yes same circuit.

I did not ground the units, although the thought did cross my mind. I'll give that a try.
Thanks.

[Kevin D]

Is that a Fios box, or something else? I know that's fiber, but is it actually copper to the box? Try disconnecting the service line to the box.

Kevin D.

[Dougie Fresh]

Something crazy here, only a few things plugged in and getting a hum!!!
I might have to run power right from electrical box!


Looks like we posted at the same time - yes Fiso that's the only thing left!!

[Dougie Fresh]

I think your on to something KD, the noise stopped when disconnected feed to Fiso box.

The sound also came from the DVD player, both were HDMI so the hum was carried in those cables (up and around).
Of course I removed the HDMI cables, but that didn't help a bit.

I'll try a different Fiso box next.


I did ground the pre-amp, which seemed like a good idea.

[Dougie Fresh]

That was frustrating - but did find a fix.

made a ground wire with eye terminal - removed thin cable-in nut and slipped it over, the other grounded.

The hum noise is fixed - HDMI is ok.

I need a two channel pre-amp that will work with a Fiso box; $100 DACs don't work, unless somebody knows one that will.

[TimbaLand]

I had the same problem and later found that I was using video RCA cables. They are not as shielded as audio RCAs. When I changed to audio RCAs the humming stopped straight away. Most of us have cables that are lying around and we just grab whichever is available because it fits in the hole. You may have done the same also or the salesperson sold you the video RCAs instead of audio RCAs

[Dougie Fresh]

Not using good cables - but the grounding worked well.

My guru buddy sent this - Expensive!: http://www.21best.com/21_best/electr...ale_.html#CATV

I'll be grounding Fiso boxes from now on.

btw did check the ground block in basement, looked fine to me.

[wkhanna]

Expensive, indeed.
Better in my mind to treat the cause rather than the symptom.
In this case, insuring all the units are at the same ground potential seems to have been effective.

[PewterTA]

Have you tried (instead of RCAs from the Fiso STB to the Pre) using SPDIF optical or digital coax and see if it happens...might fix the problem.

[madmac]

Have you tried (instead of RCAs from the Fiso STB to the Pre) using SPDIF optical or digital coax and see if it happens...might fix the problem.

That IS the beauty of Toslink optical connections. NO HUM !...... Impossible.

[Dougie Fresh]

Need stereo pre-amp that will work with Fiso (or no move night for us).
With digital optical inputs

My buddy was saying a Rotel 1056 would work with anything. (I need to goggle it, don't know anything about them)

[Kevin D]

You actually need to find out what's improperly grounded.

Kevin D.

[wkhanna]

....Better in my mind to treat the cause rather than the symptom.

You actually need to find out what's improperly grounded.

Kevin D.

Agreed.

[Dougie Fresh]

Yes Yes - but it is gone 100% maybe the cable/ends in the basement are lose.

btw All new wiring - I ripped up every piece of old coax before installer got here (you should have saw the look on his face) :heh:
For those that don't know, cable guys, whomever, will use whats there and "tap" into it.

(I helped the guy run new wires)