Harsh S's in sound using satellite box - CTC-5

[frenchy]

Hi everybody, I havent' posted here in a while.
I was told there may have been discussions in here regarding distorted sound when using newer converters/boxes on old sets. I am having a problem with harsh S's on some channels of Direct TV on my CTC-5. Doesn't do it on every channel; I'm using a Direct TV box routed thru an AC-powered RCA-to-RF box and then into the antenna connection on the TV. Any suggestions? Seems like it may be an issue other than a problem with my particular TV, since some of the satellite channels sound perfectly fine. Never had a problem when using an antenna or vcr/dvd units on it either.
Thanks!
Frenchy

[andy]

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[frenchy]

If it was the set's fault, I wonder why it wouldn't do it on every satellite channel, or on antenna or other sources either. Even seems to vary by the content of a given channel (show vs. commercials etc.)
I've tried tweaking the AGC, the 'sound reject', and the fine tuning, none had any effect on the scratchy, loud S's.
Today I also tried unplugging one of the L/R channels (since it sends stereo from the sat box to the RCA/rf box)... noticeable reduction in volume, but no real difference in the harshness on the channels that are doing it.

Would be cool if I could wire up an RCA socket to the right place in the speaker amp section so that the RCA sound output from the sat. box went directly to there, so that tuning and RF could be taken out of the equation if I wanted... but I would be worried about the chassis being 'hot' and all the high voltages. Would there be a safe place to attach an RCA socket for this, and where the volume control on the set would still work?

[old_tv_nut]

Quickest diagnosis would be to hook the satellite box and modulator to a different set and see what happens. Some reason why you can't do that?

[zenith2134]

Thats true. My Zenith DTT900 has a harsh and silibant 'S' too when used with any set. Whatever. I think it's some issue with the digital broadcasters at this point, and not the receiving hardware. Could be a cheap D/A converter too. (Well, of course its cheap, given the pricepoint...)

[N9ZQA]

The Zenith (and also the Insignia) DTV boxes have a known problem in boxes with a manufacture date before April 2008. Some of the guys at AVSForum have been following this issue with some interest. See this link for more info..

http://www.avsforum.com/avs-vb/showt...php?p=13892772

-Jim

[zenith2134]

Thanks man. I'm going to read this through later.

[Phil Nelson]

Originally Posted by frenchy

If it was the set's fault, I wonder why it wouldn't do it on every satellite channel, or on antenna or other sources either. Even seems to vary by the content of a given channel (show vs. commercials etc.)

"Audio buzz" is a common problem in older B/W sets and it certainly can vary depending on the source and also the content.

We have a satellite TV system (Hughesnet) and the audio volume does seem to vary from one channel to another. Noticeable even on our modern plasma TV.

Tweaking the AGC and the alignment is a good place to start.

On a couple of my older B/W sets, you can get bad audio distortion if you suddenly switch from a low-contrast scene to a high-contrast scene, such as big white letters on a black background. This is especially noticeable in my RCA 630TS, which has manual gain control rather than AGC. That set was aligned by a retired TV oldtimer, so alignment is not the issue. You can reduce the buzz by turning down the manual gain, but it's something you just have to live with, on such an old set.

Some DVD or VHS players can also overdrive the signal, creating buzz. I have never tried connecting a vintage TV to our satellite box, but it wouldn't surprise me to hear some buzz (or other distortion) from time to time.

A few years ago, I found an RF attenuator at Radio Shack, which you can use to reduce the output from a source. It's a little metal box with a More-Less knob on the front. Not sure what's inside -- perhaps just a potentiometer. Anyway, it works to reduce a too-strong signal.

I have been following the Zenith/Insignia DTV converter discussion (well, as much as I had the patience to read). Not sure if has any magic bullet solution to your problem, since it's specific to DTV converter boxes.

If your set sounds perfect with an antenna signal, but imperfect using the satellite receiver, perhaps your TV is just being overdriven. Those old sets were designed to receive antenna signals over the air. Some modern devices just seem to swamp them.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[compucat]

I get the same problem with distorted "S" sounds and on one channel the audio sounds overmodulated. I am using a Magnavox DVD/VCR/DTV combo with rabbit ears hookeed to my Zenith roundie. It must be one of the many imperfections of digital TV. When I use the Zenith's built in tuners I get proper audio on all channels.