Digital TV, poor sound

[Cornucopia]

I agree with the posters above (jagabo, jman98, edDV, usually_quiet, paulyvee). I'm pretty sure it's either something in your specific setups/settings, or your hearing, or both.

I've had Comcast for ~4 years now, and, although it certainly isn't what you'd call PERFECT, it is usually very, very good for compressed, digital material. No complaints at all (except for one time about 2 years ago where something screwed up at our local headend and the sound was atrocious for ~2 hours!).
I am also a long time Audio Engineer, with 2 Comcast Boxes w/HDDVR, 3+ BD/DVD players, and Internet connected, some to TV alone, some to HT Amp alone. NO PROBLEMS. Much enjoyment. Nothing changed with the Analog Sundown/changeover here. It was quite anti-climactic.

Don't mean to insult, but HOW OLD ARE YOU? (I'm 50, so I understand others asking about age-related accuity falloff).

IIWY, I'd take the suggestion of paulyvee and "get back to basics" with a simple setup that includes just known GOOD devices (e.g. OTA Digital TV alone, or DVDPlayer+Monitor, etc), then SWAP or EXPAND to compare until your whole setup is back to normal.

Also, when someone here asks for Technical Info with which to assist you, if you continue to just "GladHand" with generalities instead of actually divulging the true specs and layout, it begins to look a little suspicous (at least to me). Model #s, Facts...That's what we need.

BTW, the changeover occurred Feb 2009 (with some places getting a stay until June/July 2009), so it's not 1 year ago, or 3 years ago, but 2 years ago.

Scott

[Derryanna]

Thanks for your help, Cornucopia.

Dee

[edDV]

Paulyvee, hello from across the Pond!

The digital age was met with great anticipation hoping for even better pictures on our TV's. Indeed, the change in audio did happen during the few days after the Comcast Repair man opened the Juction Box which was about 3 blocks from our home. He changed the AFC or AFG (I never can remember the proper name) switch which had something to do with 'balance', and, he found water in the box. The reason for the repair was we were without TV for 8 days due to only pixels showing up on the TV screens. We gained back our good TV, but, shortly after that (or, the digital age), we found the Audio causing problems.

This would all be Comcast specific. Each Comcast neighborhood has a different history since they consist of a series of local acquisitions. I'm lucky to be on a near state of art Comcast fiber to last mile infrastructure (leaving out a long CA politics diatribe i.e locals no longer have control of cable in CA, it is now run by political contributions).

Yes, our Neighbors tell us they are not experiencing the problem though one would think the Junction Box repair would affect all.

We only use our Receivers/Speakers in one room, preferring the simplicity of just listening to the speakers on other TV's. The Audio is bad no matter which we go.

Also, remember, even our DVD audio is affected as I learned today, by entirely disconnecting the Comcast cable to the TV, and found that the DVD still gave out that muffled, in a cave, sound.

Bingo - suggests issues are inside the house. Nothing suggests Comcast.

Now I have several Comcast complaints but not these.

Yes, all makes and models in five different rooms are affected.

All equipment is of top Brand and quality, even the older 1982 Zenith which we rarely use. It is for admiration only being these types of cabinets are no longer made. Chuckle!

Please, it would be of great pleasure to have you detail a suitable diagnostic approach.

So far, the worthy words from 'jagabo' and 'usually quiet' have been of much interest as every instinct I have tells me this is encompassed either outside of our house or something gone wrong inside our house.

Please join us and help.

Dee

You need semi-professional help*. Nothing here suggests it is a Comcast issue.


*Most likely a neighborhood geek A/V teen.

[Derryanna]

Laugh! edDV, it was not that long ago that I was the neighborhood geek A/V teen. My, what happened to all that time gone so quickly.

[Derryanna]

Laugh! edDV, it was not so long ago that I was that neighborhood geek A/V teen. My, how fast the time goes..............

[jagabo]

Another possibility would be blown tweeters. But most TVs don't have multiple drivers and you wouldn't expect several TVs to all go at once.

[Derryanna]

My last action is to just go room to room and unplug everything in those rooms. Then I will choose one TV and replug that one. If I hear no distortion, I will then go to the next of the 5 TV's until I hear bad audio.

[Cornucopia]

That's your idea of troubleshooting?

No wonder the Comcast dude "raised his eyebrows" at you. Still no facts, I give up.

Scott

[usually_quiet]

BTW, the changeover occurred Feb 2009 (with some places getting a stay until June/July 2009), so it's not 1 year ago, or 3 years ago, but 2 years ago.

Scott

Comcast's analog cable service really was discontinued almost three years ago in a few cities. Comcast began the process of moving all their customers to digital service in the latter part of 2008, although it did not take place in most service areas until 2009 or 2010. Comcast was supposed to complete the conversion for all service areas in 2010. I don't know if they finished on schedule.

FCC regulations do require cable TV providers to supply the primary subchannel of all local full-power over-the-air stations in analog form until 2012, unless they qualify for an exemption. Beyond that, cable TV providers are free to provide as many or as few analog channels as they want to.

The over-the-air analog to digital changeover that took place between February and June of 2009 was mandatory because of federal legislation requiring it to occur, while Comcast's decision to just offer digital service was purely a business decision. Unfortunately, many Comcast customers were confused about the federal government's role in the switchover because of the timing.

[Derryanna]

Usually Quiet, thank you so much. Yes, we were first on the digital list. As to your chosen name, I see why you have it.

"it pays to be quiet until there is something important to say!"

Thank you again.

Dee

[Cornucopia]

BTW, the changeover occurred Feb 2009 (with some places getting a stay until June/July 2009), so it's not 1 year ago, or 3 years ago, but 2 years ago.

Scott

Comcast's analog cable service really was discontinued almost three years ago in a few cities. Comcast began the process of moving all their customers to digital service in the latter part of 2008, although it did not take place in most service areas until 2009 or 2010. Comcast was supposed to complete the conversion for all service areas in 2010. I don't know if they finished on schedule.

FCC regulations do require cable TV providers to supply the primary subchannel of all local full-power over-the-air stations in analog form until 2012, unless they qualify for an exemption. Beyond that, cable TV providers are free to provide as many or as few analog channels as they want to.

The over-the-air analog to digital changeover that took place between February and June of 2009 was mandatory because of federal legislation requiring it to occur, while Comcast's decision to just offer digital service was purely a business decision. Unfortunately, many Comcast customers were confused about the federal government's role in the switchover because of the timing.

I see - you read the "Changeover" bit to be referring to Comcast-specific, I read it to be referring to OTA-specific. Since the OP mentions both on a number of occasions, I can see the confusion.

[Derryanna]

Paulyvee, have you forgotten me? Everyone has been very helpful and I would like to see your step by step instructions, too.

[TBoneit]

Snipped
Also, remember, even our DVD audio is affected as I learned today, by entirely disconnecting the Comcast cable to the TV, and found that the DVD still gave out that muffled, in a cave, sound.
Dee

It seems to me that you need to stop blaming Comcast.
There is no way they can have any effect on a DVD playing.

Good Luck

[Derryanna]

TBoneit, yes, if you read all the Answers you will see I have long since forgotten Comcast. I am waiting for Paulyvee to contact me with how to check our home which seems to be the problem.

[paulyvee]

So what's with the "Paulyvee have you forgotten me?"!!!!

Remember the time difference. I have to do a bit during the day to satisfy "She who shall be obeyed" -better known as Herindors (HER IN DOORS) and I am answering at the same time as I was online yesterday - 01:00 or 01:00 am to those with only a 12 hour clock.

Right !!.
Back to work
When can I book a house call.??
It shouldn't cost more that a couple of thousand pounds - 4 or five thousand dollars for the air fare etc.
I could do with a break from her indoors as well
No?
Shame!! it was worth a try though.!!!

Given that the fault is not you yourself - you fussy "person" and that the acoustics are good. or at least have not changed to cause the problem you need to eliminate any environmental factors.
Not as silly as it may sound.
I had a client who wore a hearing aid and complained that it was distorted in his own home but worked perfectly everywhere else.

The problem turned out to be a local TV booster station (rebroadcasting to a small area of normally poor reception). This transmitter was mounted in a street cabinet outside his house and was being received by his audio only hearing aid - rectified internally and overloading one of the preamp stages.

The cure - a tinplate tobacco tin.
Whenever he was home he used to carry the hearing aid inside an ordinary tobacco tin which acted as an RF screen and eh Viola....

A client complained of no TV every friday night.
That job drove me nuts!!!

He lived right out in the sticks in a farm cottage with no bathroom.
His next door neighbour's bath night was friday night.
He used an indoor aerial which only worked by receiving a signal reflected off the tin bath hung up in his neighbour's outhouse.
Take the bath down to use it.------ no TV.

This was cured just as easily - cooking foil on the outhouse wall behind the bath.
Easy when you know how.

A third job was a guy who brought in his amplifier for repai. I repaired it asn soak tested it for an hour or so - a good excuse for some workshop music.
The lad collected it and two days later it was back with exactly the same fault. Repaired - soak tested and the client had a good play before leaving with it.
Next day it was back!!
I did a home visit and discovered a huge spike on his incoming mains.
The local electricity substation had a loose connection and every time a local garage sparked up its electric welder it spiked the mains to more than 1500 volts - all my kit could measure and blew the output transistors in his amp.

So environment can count a lot.

As a first stage disconnect all the kit.
Reconnect just the TV.
If it has a baseband audio input provide a reasonable quality signal from a battery operated piece of kit - a portable radio or cassette player.

The battery operation is important. It eliminates the possibility of any floating DC or AC signal being introduced from the electricity supply causing any low frequency hum possibly below audible level or of any hight frequency (above audible) signals producing any intermodulation products.

In Europe input signals are usually 1v rms - and fed via a dedicated connector - the "SCART" connector.
I understand that in the States most audio interconnects are via "pin" plugs - the "RCA" connector or similar.
Watch signal levels to prevent preamp overloading.

Obviously there will be no picture and operation may shut down if there is any switch off timer - reliant on a video signal being present. However these usually take 5 minutes or so to cut out and that is enough.
You can expect that the output will not be anywhere near Hi Fi quality as the amplifier in the TV is optimised for the limited bandwidth signal provided with analogue TV.
The effect will most likely be a bit "boxey" - poor booming bass and a bit dull in the treble region.
The normal "European" analogue TV signal was light on bass to reduce the bandwidth of the FM carrier and prevent intermodulation with the video signal - it was carried as a 1.5mhz subcarrier.
In the States I understand that transmission was similar but using a 1mhz AM carrier.

If the results are poor ignore the TV sound chain and use an external amplifier for sound.

If the results are reasonable carry out the same test with a HI-FI quality mains derived base band audio signal.

If the results are then poor one would suspect that the tone control stages in the TV - put there to tailor the sound response of the cabinet - speaker to make the TV sound chain sound good even though most TV's have crap speakers and amplifiers in them.
A bit of tweaking by the manufacturers worked wonders in the analogue world.

The most likely cause of your problems should have by now been illustrated.

If as I suspect the problem is the bandwidth of the digital signal - no matter how encoded they are mostly wide bandwidth and cause a lot of intermodulation within the amplifiers which cannot handle the flat response "relatively" high level bass signal for example having been designed for the restricted bass and treble provided by analogue transmissions If tis is the problem you can expect crap when you drive the system with a Hi Fi signal - one with a flat bandwidth.

The first test with the ordinary portable signal source will not necessarily show the effect as if will have a tailored amplifier response to match its small speaker.

Let me know how you get on.

All the best

Paulyvee

[Derryanna]

Pauly, before I make arrangements to begin following your instructions, keep in mind that I have 5 Television sets, all having the same over amplified base sound. All five! I discounted our Cable company as I disconnected one of my TV's from the Cable and connected a DVD Player to that TV and shockingly still heard the amplified sound from the movie. We have now had 3 Neighbors listening, also, and they hear the difference in our TV's from their's.

By the way, you should really write a book. We loved reading your experiences. Your wife has to really love you so ...... take care. Chuckle!

Dee

[paulyvee]

An afterthought - If the first test show a problem - before scrapping everything pack your kit in you car and take it to a friend a good distance away to eliminate effects due to the immediate locale.
Repeat the tests first with the battery source then the hi-fi source.

After this stage we can start to look at the RF signal chain.

[Derryanna]

Oh, Pauly, please forgive me and remember I live in a foreign country......America, so, what is a "kit"?

Dee

[paulyvee]

I have taken the fact that there are multiple units which are suspect into account when recomending that you start with the audio chain.
ALL analogue TV,s that I have ever worked on and available in Europe - that's a lot of TV's by the way - have had a tailored audio response and in fact on my own TV I had a similar problem with the internal speaker - a reasonably cheap but current flat screen unit with a speaker smailler than that fitted in my six year old nephew's portable radio.
And that is a TV which is supposed to be digital ready with a built in digital tuner.
I would suspect that most if not all American TV's are the same.

[paulyvee]

Kit - a piece of kit is British for a piece of equipment. All your suspect kit is all of your suspect equipment.

[paulyvee]

I take it by the way that I don't get the invite for a home visit.

As the well known Muttley says - DRAT and DOUBLE DRAT!!!

I used to know a load of Yanks when I was at school - **** years ago. They were the kids of the Yanks at the local American Air Base. once we had learnt to translate what they were saying into "real" english "like wot we spoke" we used to get on well.

I suspect they never understood us as well as I lived in a farming community in Berkshire - pronounced BARKSHIRE by the way- with a quite distinctive accent and even other parts of England don't understand us locals.

[usually_quiet]

Oh, Pauly, please forgive me and remember I live in a foreign country......America, so, what is a "kit"?

Dee

"Kit" would be equivalent to "gear" on this side of the Atlantic, or more formally, "equipment".

[Edit] Sorry for typing out of turn. I though paulyvee had left for the moment.

[paulyvee]

If the fault shows up with the simple audio tests so far detailed it is almost cirtainly due to the flat response audio signal driving a receiving chain with a response tailored to the bass light poor treble transmitted by analogue TV stations.
Three possible cures.
a) ignore the internal TV sound and provide a separate sound system.
b) redesign the audio channel on the TV's . Relatively easy on older sets with analogue volume controls.
If the volume control input signal is disconnected and a small unity gain "Radio Shack" style mixer - tone controller inserted in line this could be adjusted to the inverse of the tailored response to flatten it.
Not so easy but still possible on more modern digitally controlled sets - identify the chips in the audio chain and apply to the makers for applications data which will detail all mods required.
c) Live with it!!!

[paulyvee]

No apologies sought or necessary!!
A good translator is a necessity when dealing with you foreigners.!!!

[paulyvee]

By the way Cornucopia - the idea of disconnecting everything and starting from scratch is not the last resort but the first. With a fault over a number of bits of kit there is certain to be a common problem - not individual faults. If it were to be a networked system it could be a fault on any one of the units affecting others - for instance any one unit could put an AC signal on line - potentially inaudible but enough to produce intermodulation distortion or there could be a hum loop - a ground loop to foreigners - doing the same thing when multiple units are connected.. This is not always cured by earthing everything - in fact it can be caused by too many earths. The idea of working on one bit of kit alone gives you a chance of resolving it instead of chasing you tail.

[Cornucopia]

@paulyvee,
Maybe you misunderstood me. I never said "as a last resort". I would agree you need to START with simplicity that you can easily verify, then expand upon it slowly but surely.

I also agree it could be a ground loop (aka "too many earths").

Scott

[paulyvee]

Not so sure about that. I am almost sure that it is an incompatibility problem - an audio response tailored for analogue TV being used for the flat frequency response digital signal.
This would be born out to a degree with Derryanna having problems with a DVD player - certainly newer that the Zenith tv of 1980's vintage and probably with a much flatter frequency response.

[paulyvee]

Derryanna
In the 1980 there was a program on British television called Minder. It was about a Cockney con artist and his bodyguard - his "minder" Throughout the life of the program you never saw the con artist's wife. He always referred to her as "erindors" - "Her In Doors" . Hence the nickname for she who shall be obeyed.

Besides which I daren't ask her if she loves me - she might tell me the truth.

We have been together for 30 years and are still speaking to each other so that must count for something.

I bought a canal boat some years ago but when I wanted to rename it ERINDORS the frying pan hurt.
Besides which I hate the site of blood - particularly mine.Plus the fact - she's bigger than me and I am a devout coward.

How are you getting on checking out your system??

Paulyvee

[Cornucopia]

Not so sure about that. I am almost sure that it is an incompatibility problem - an audio response tailored for analogue TV being used for the flat frequency response digital signal.
This would be born out to a degree with Derryanna having problems with a DVD player - certainly newer that the Zenith tv of 1980's vintage and probably with a much flatter frequency response.

Yeah, but I don't think that accounts for the "hollow" and "muted, cold-in-the-head" impression the OP remarked about - that sounds like comb-filtering or flanging due to some kind of multipath interference.

Scott

[paulyvee]

Exactly the effect you would expect when over driving an amplifier with a bass heavy signal.
The cross modulation expected from the very low frequencies - below the expected performance of a TV sound system causes a flanging effect when the low frequencies overload the system and push the amplifier into non linear amplification of the midrange frequencies. Scott
Scott
Remembering a true flanger is a variable gain amplifier utilising a low frequency as the gain control signal. Admittedly in a true flanger the modulating signal is dealt with on a separate control line. If the modulating signal is present in sufficient amplitude electronically but below audible levels because of inadequate acoustic frequency all you would hear is the cross modulation products. - a flanger on the cheap.
The same effect could be produced for instance with poor reservoir capacitors in the power supply where some of the hum produced is due to direct injection into the signal line and some of the hum is produced by the variations in gain in gain as the supply varies.
This effect is illustrated by the increase in cross modulation with poor reservoir capacitors.
The potential bandwidth of a digital audio signal is from 20 Hz to 18 - 20 KHz - the bottom end of which is way below 100 - 200 Hz expected from even a half way decent analogue TV and therefore effectively inaudible

Paul
paulyvee