Help me understand the isolation in True sub voltage tracking amplifier

[wonderfulaudio 1]

Hi,

 

Please see the schematic https://thecarversite.com/manuals/Sunfiremandir/Sunfire Schematic Subwoofer TS-EQ.pdf

In page 3, U9 CNV17-1 optocoupler seems to be isolating the high voltage amp from the audio input, but 

a) How is the optocoupler used for audio as it is not a linear device needed for audio?

b) R158 and C144 are connected between low voltage input side to high voltage output side, what are they used for?

c) Dont R158 and C144 break the isolation?

d) On page 5, BR1 inputs are shorted, this looks like a typo mistake or older manual

 

Thanks and Warm Regards,

WA

[Nahash5150 10,984]

On 1/27/2026 at 7:27 AM, wonderfulaudio said:

Hi,

 

Please see the schematic https://thecarversite.com/manuals/Sunfiremandir/Sunfire Schematic Subwoofer TS-EQ.pdf

In page 3, U9 CNV17-1 optocoupler seems to be isolating the high voltage amp from the audio input, but 

a) How is the optocoupler used for audio as it is not a linear device needed for audio?

b) R158 and C144 are connected between low voltage input side to high voltage output side, what are they used for?

c) Dont R158 and C144 break the isolation?

d) On page 5, BR1 inputs are shorted, this looks like a typo mistake or older manual

 

Thanks and Warm Regards,

WA

 

a) this is not a full range audio device, it's a sub and has a brick wall low pass filter at 200Hz

b) likely required by UL/IEC for safety from static electric discharge on the processing side

c) only when it needs to, to prevent catastrophe

d) It's a half-wave circuit - it just look strange because it's illustrating a full-wave device.