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

"Ant" <ANTant@[EMAIL PROTECTED]
> wrote in message 
news:482914cb$0$30481$4c368faf@[EMAIL PROTECTED]
> On 5/12/2008 12:56 PM 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.

David