Re: Confused on which DTV converter box... (Zenith Box Audio)

On 5/13/2008 6:50 AM PT, David typed:

>>> I have a DTT900 Zenith box (Feb '08 manufacture) and there is indeed 
>>> an audio problem on the baseband audio from the RCA jacks. It appears 
>>> they apply the 75 micro-second pre-emphasis to the audio as required 
>>> by the NTSC standard for the channel 3,4 modulator, but also send the 
>>> pre-emphasized audio to the RCA baseband outputs. The error is in 
>>> both channels (not just the left channel as re****ted on some forms). 
>>> The board layout allows an easy fix for this. The series impedance 
>>> between the audio driver and the output jacks is 4300 ohms composed 
>>> of 1K and 3.3K resistors. You need to shunt the audio outputs with 
>>> 0.018 microfarad capacitors to get the response flat. If you are 
>>> handy with soldering surface mount capacitors, there are places on 
>>> the top of the board to mount them. If not, you can solder leaded 
>>> capacitors directly across the audio outputs on the bottom of the 
>>> board or use external capacitors.
>>
>> Am I going to notice this problem with cheap/TV internal speakers? Or 
>> are these only noticeable on high-end speakers?
> 
> I do not believe there is any audio problem when using the channel 3,4 
> RF output (which is only monaural) and the box is also placed in 
> monaural mode using the option menu. I admit that I have not tested that

> exhaustively on a variety of TV sets. If you use a baseband connection 
> with the red-white-yellow connection, you may hear the excessive high 
> frequency problem on even a cheap TV. 75 microseconds corresponds to a 
> 3db increase at about 2.1 KHz, an additional 4 dB rise at 4.2 KHz, and 
> an additional 6 dB rise for every octave above that. At 10 KHz the boost

> is over 13 dB so this is a significant departure from a flat response.

Hmm. Can't be worse than VCR and VHS tapes audio quality. :)
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