Connecting TV to external speaker produces buzz/hum

Hi, I hope I'm posting in the right place ... I'm a newbie, not exactly wet behind the ears but by no means expert - and experiencing an annoying problem:

I have a Prosonic flatscreen TV with built-in DVD player, a Vantage 8000 satellite receiver, and a Bose SoundDock II loudspeaker unit. The satellite receiver is hooked up to the TV via a scart cable. I want to use the Bose to enhance the TV sound.

When I connect the sat receiver (from red and white RCA output sockets) to the Bose (3.5mm jack plug input), the Bose produces excellent, clean sound to accompany the channels I am watching on the TV.

But when I try linking the TV directly to the Bose in order to be able to play music CDs in the TV unit, there is a loud hum while the music is playing.
To link the TV and Bose I am using a male 3.5mm jack FROM the TV headphone socket TO a male 3.5mm jack into the back of the Bose.
But, as I say this is creating a buzz. Is it possible that the TV amplifier is disagreeing/clashing with the Bose amplifier?

The TV also has an orange-coloured socket ("Coax Audio Out"). Is this the connection I should be using?

Thank you for any advice you can offer.

Thank you, Espo77

I already have the TV turned down to 0 (zero) volume, adjusting exclusively by means of the Bose volume control (making finer adjustments by means of the sat receiver remote if watching programmes unit with the receiver connected directly to the Bose - but, as I say, it's the TV -> Bose connection that's giving me the buzz/hum problem).

Audio settings in the TV menu are:

Volume Setting : 0

Sound Effect Setting :
BBE
SRS
Normal (this is selected)

SPDIF Setting :
OFF
PCM (selected)
RAW

Any clues here?

As far as I can judge, the only OUT sockets the TV has are: (1) 3.5mm headphone jack, and (2) orange "Coax Audio Out".

Thank you again.

I grabbed your suggestion with both hands - and for a few moments while I was making the volume adjustment I thought we were home and dry. But alas, the buzz/hum is still there ... slightly less audible because the Bose is turned to a lower volume and the TV is turned up. But definitely there.

As a test, I also reconnected the sat receiver directly (from red-and-white RCA OUT sockets to the Boze's 3.5mm IN socket) and that is still clear as a bell, great audio and no buzz.

So back to the drawing board ...

I keep wondering about that orange audio OUT on the TV. What is that for? I feel tempted to buy a cable to connect from the orange "Coax Audio OUT" to the Boze's 3.5mm IN but I'm afraid to try something I know absolutely nothing about in case I damage/blow one of the units.

Any info at all on the orange audio OUT?

Sorry for delay in responding, guys ... have been tied up with work.


Espo77 : “The question is, does the Bose have a digital coaxial input, or better yet a toslink/optical connection on both devices. The optical is pretty much a noise free connection.”

The ONLY input on my Bose SoundDock II is a 3.5mm IN socket, which I think is analogue ... so a toslink cable would presumably be no good here (I’ve just googled “toslink” and found it is for optical connections).

Espo77 : “I keep talking about controlling the two volumes on the two devices ...”

Yes, I’ve done some experimenting with that, and I can get the buzz down almost to the inaudible level – but not silent completely. I'm not sure that is the long-term solution unfortunately.

Espo77 : “... also you can come "out" of the set top box with various connections, and hook to the "in" on the Bose. This might help to trouble shoot.”

Red+white RCA jacks FROM the set top box TO the Bose (3.5mm socket) is no problem. Pure audio, no hiss/buzz/hum. It’s TV to Bose that’s the headache.

Selden Ball : “If they aren't already, plug all of your audio equipment into the same outlet (i.e. into the same power strip). Buzz/hum is usually caused by a "ground loop". This usually is caused by plugging audio equipment into two different power outlets in your home. Most homes are provided two separate power phases (of the three available) by the electric company. All audio and video equipment needs to be plugged into the same power phase.”

I’ve just checked my setup ... the Bose was in a different power socket so I collected everything (set top box, TV, and Bose) on a single power strip. I "think" there was a slight improvement but again not completely solved. There is still a fairly audible buzze from the Bose when the TV is providing the input.

Chikoo : “TV 3.5mm headphone --> Bose 3.5mm IN should work best for you.”

I’m afraid that’s one of the cables I have tried (male 3.5mm at each end) ... buzzzzz/hummmmm ...


A thought occurs to me: I bought this (Prosonic) TV in Denmark a few years ago and brought it to Scotland, where I now live ... maybe there are special electrical conditions there that differ from where I am now (although I’ve never noticed anything previously). I’ll make some inquiries on a Danish forum, see if anything turns up.

I've looked around some Danish sources but have not found any useful hints or pointers which could indicate a solution to my problem.

Today I have ordered a pair of new, small speakers (Creative Gigaworks T20 Series II, approx. GBP 50 / USD 65), which I shall try in place of the Bose (which cost considerably more). Will report back when I have some results.

Because the TV has a DVD/CD player unit built in. I would like to be able to play a DVD or CD in that unit and have the audio played through the external speaker (= Bose). At the moment, that's when I get the buzz/hum. So I am having to revert to the TV's rather miserable built-in speaker(s) when I watch a DVD (OK, that sounds as if I have nothing better to complain about than poor speakers versus better speakers but ... it's tempting to aim for something better when you just know that the system can produce it ... ...)

I've just tried something new today as I wait for my new Gigaworks speakers: I connected a cable FROM the headphone output on the tv TO a pair of simple laptop speakers (instead of the Bose) - and the buzz/hum was still there when I played a DVD ... proving (at least in my own mind) that the problem is not in the Bose but is either (a) within the tv (including the DVD unit), (b) in the tv headphone socket or (c) in the 3.5mm jack cable connecting the socket to the speakers.

I think you're all getting closer to the problem! I've been trying different combinations for the past hour.

JD in NJ : Have you tried just plugging a pair of actual headphones into the headphone out jack on the TV? It would be nice to know if the sound is clean that way.

I've just tried that one minute ago (after reading your suggestion) ... nothing, zilch, no sound is coming out of the headphones at all, neither clean nor dirty.

Espo77 : ...so, why are you buying new speakers??

The Bose SoundDock belongs to my wife (for her iPod) - I've just borrowed it to experiment with for a couple of days. She's getting impatient to have it back ... that's why I'm buying (my own!) new speakers.

Espo77 : Sounds like the problem might be within the combo TV/DVD player. Try hooking up a new seperate DVD player.

I think that's definitely part of the problem. Haven't got a separate DVD player but I hooked our small kitchen LED tv via the 3.5mm double-ended jack cable to the Bose, and that combo produced clean audio. So that pointed the finger at the lounge tv and built-in DVD unit. But see response to Chikoo below ...

Chikoo : The tv needs a better grounding solution or a filter. I had the same issue with my car's audio out. The dealer put an inline filter to rid of that buzz/humm. Check out inline filters and order one.

After testing the kitchen tv, as described, I took the gear back to the lounge and started fitting bits together. With the 3.5mm cable in the back of the Bose, I accidentally touch the other end of the cable with my finger - and it produced a faint but distinct buzz from the Bose. Doing a bit of experimenting, I found that when I touched the tip of the cable and touched the metal cover of the sat receiver, it produced exactly the loud buzz/hum that's been giving me a problem. So there is definitely some kind of grounding/earthing issue - which is way beyond both my understanding and my capabilities.

So I came back to my computer to report to you guys

I'm afraid this thread is now 'way over my head. Not the fault of you guys, I realise that, but I just can't follow what's being said and advised.

Bill Fitzmaurice : Lifting the ground shield on the audio cable might fix his problem; an audio isolation transformer made for the purpose is another option, as is an isolation transformer between the cable box and TV.

Bill, realising that your post was directed primarily towards Selden Ball removes some of my despair at not understanding much of what you are talking about. But comparing it with Chikoo's two posts following yours, I am guessing that you are recommending a filter which fits between "somewhere" and "somewhere else". But sorry, I am out of my depth.

Chikoo : Check out inline filters and order one. Example here: PIE EIS-ILNO In-Line RCA Audio Noise Filter/Ground Loop Isolator.

Thank you, all of you, for spending so much time and effort in getting me this far. I'll visit a local audio shop now and get them to sort it out - but, thanks to you, I have a better understanding of the problem, how to describe it, what terminology to use and listen for. I'm happy to close the subject here

PS : Just in case anyone is reading this thread later with the same problem, in addition to the advice given above the following link may be helpful:

http://www.ehow.co.uk/info_8723810_d...se-filter.html
.

Problem solved!

I took the tv and Bose speaker along to Perth Car Radio Services (where they fix car radios). Fortunately my setup buzzed when the guy set it up. He tried a new lead from his own stock (3.5mm jacks each end) between tv and Bose - that one buzzed, too, and he pronounced the headphone socket to be "dirty". He suggested that instead of taking the audio from the headphone socket I could try taking it from the scart socket on the tv by fitting an adapter: Scart to RCA (it has a switch which allows the scart to either input or output the signal) and feed that output signal to the Bose with an RCA -> 3.5mm cable. Got an adapter at the local Asda (= Walmart) for GBP 6 (about USD 10). And it works perfectly.

Thanks to all for your help.