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Audio out Mod Cap?

Doomguy42

Member
Hi,
Does anyone know what this extra Ceramic cap would be doing? It's on an audio out channel after all the processing. It's over the top of a 100k Resistor, next to a 100nf ceramic cap then finally the AMP.

The Channel next to it doesn't have the mod. It's dual L+R channels but it was never used for stereo sound... its mono then a separate channel for an Alarm (Max volume).

Would this be used to maximise the pre amped volume for the Alarm?

The value is too low to register on my meter.
(Scrap board in the picture)

Thanks
 

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If the 100k affects signal gain or attenuation then reducing to 10k would boot the amplitude by x10
If the alarm was say at 3kHz that might be a 5 nF cap.

This 4D log scale RLC-f graph demonstrates this like an old slide rule without the math.

100k // 5nF forms a high pass filter that maybe boosts the gain above 300 Hz so that at 3kHz it is 10x more sensitive.

This is a hypothetical answer

1701819037686.png
 

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