Philips 27PS60S321 manual Audio Signal Processing, Stereo, Mono

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Figure:

The S8/T8 is divided into 2 basic systems, i.e.mono and stereo sound. While the audio processing for the mono soundis done in the audio block of the UOC, an external audio processingIC is used for stereo sets.

The tuning system features 181 channels with on-screen display.The main tuning system uses a tuner, a microcomputer, and a memoryIC mounted on the main panel.

The microcomputer communicates with the memory IC, the customerkeyboard, remote

receiver, tuner, signal processor IC and the audiooutput IC via the I 2 Cbus. The memory IC retains the settings for favorite stations, customer-preferredsettings, and service / factory data. The on-screen graphics and closed caption decoding aredone within the microprocessor, and then sent to the signal processorIC to be added to the main signal.

The chassis utilizes a Switching Mode Power Supply (SMPS) forthe main voltage source. The chassis has a ‘hot’ ground referenceon the primary side and a cold ground reference on the secondaryside of the power supply and the rest of the chassis.

Audio Signal Processing

Block diagram Audio

Stereo

In stereo sets, the signal goes via the SAWfilter (position 1002), to the audio demodulator part of the UOCIC 7200. The audio output on pin 48 goes to the stereo decoder 7831or 7861. The switch inside this IC selects either the internal decoderor an external source.

There are two stereo decoders used:

1.a BTSC DBXstereo/SAP decoder (MSP34X5 at position 7831) for the highestspecified sets and

2.a BTSC non-DBX stereo decoder (TDA 9853 at position 7861)for BTSC Economic.

The output is fed to the to the audio amplifier (AN7522at position 7901). The volume level is controlled at this IC (pin9) by a control line (VolumeMute) from the microprocessor. The audiosignal from 7901 is then sent to the speaker / headphone outputpanel.

Mono

7/8/2004