Colour Maximite 2 - Second Generation


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Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 968
Posted: 07:17pm 02 Jul 2021      

Can I ask what decided the value of 4k7 for the audio output resistors? That's a pretty high impedance output and probably wouldn't drive any commonly available headphones, although it's fine for active speakers or an amplifier input.
390R would give a maximum current of 8.5mA into a short circuit, so the output would probably be protected. It might also allow the connection of headphones as the audio output would be higher. Ok, it would put DC through the phones, but it probably wouldn't exceed 3mA or so which would be ok for most. It wouldn't give much output, but at least it might be usable and could handle down to 8R headphones safely.