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willnotwish / sony-tv-kdl32v5500-sound

Sony TV (32 inch, 2009) sound issues
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Initial investigation #1

Open willnotwish opened 1 year ago

willnotwish commented 1 year ago

Audio output in the KDLxxxV5500 series of flat screen TVs from around 2009 is handled by a class D amp in balanced mode: a TAS5602 stereo "digital" amp followed by an LC filter driving a pair of small loudspeakers.

willnotwish commented 1 year ago

The first thing to check is whether the issue is the same on all audio inputs, or only on a subset. Maybe it only happens on HDMI1, for example.

willnotwish commented 1 year ago

Rather than a vague description of the issue, it would be preferable to be able to reproduce the problem reliably.

A Sony audio DSP (CXD9926ATQ - IC7003) generates the PWM signals which are then amplified by a digital amp (TAS5602DCAR - IC7201).

willnotwish commented 1 year ago

IC7003 can take digital signals directly (e.g., from HDMI), as well as analog sound inputs.

willnotwish commented 1 year ago

Ideas for analysis/measurement of problem

Feed a pure sine wave at a fixed frequency into AV3 (L) from a signal generator. Using a scope, compare this source signal with the output of IC7201 at various points in the circuit. Also use a differential probe to monitor the waveform at the loudspeaker.

Vary the frequency. Look for distortion or modulation.

Examine the PWM signal output from IC7003.

willnotwish commented 1 year ago

I can at least feed audio from my laptop via HDMI and/or analog into AV3. It is difficult to detect differences when listening to pure frequency tones (e.g., 1kHz).

willnotwish commented 1 year ago

The fact that I first noticed the problem when listening to an HDMI source (speech from Virgin box) indicates that the analog part of the audio DSP (IC7003) need not be investigated at this time.