TG16:Turbo Duo Audio Fix

When comparing the audio signature of the original PC Engine Duo/TurboDuo to other units (such as the Duo-R/RX or PAC-N1/10), there is severe low frequency attenuation of HuC6280 audio (all channels) due to the small AC coupling capacitance used in the audio circuit.

Audio Fix Details

Step 1 - Remove ceramic capacitors C878, C879 and C883

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  C878 and C879 Location

• 

  C883 Location

Step 2 - Replace with 10 uF 0805 capacitors

Replace the capacitors using ceramic X7R 10 uF 0805 size capacitors. Tantalum or electrolytic may be used as well, but polarity must be considered and is not covered here.

Frequency Response Comparison

The difference in frequency response can be seen in the MDFourier plots shown below. Low frequency HuC6280 audio is attenuated almost 10 dB due to the more aggressive high pass filter formed by the original 100 nF AC coupling capacitors. The original Duo audio capture was performed with a Turbo Everdrive Pro and compared to a PC Engine Duo-R native CD hardware.

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  MDFourier Response - Before

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  MDFourier Response - After

Before/After Audio Comparison

Before/after audio comparison courtesy of "SquidDude" from the ConsoleMods Discord:

• File:duo_before_audio_fix.mp4 - Before Audio Fix
• File:duo_after_audio_fix.mp4 - After Audio Fix