Re: [NTLK] nearly OT - audio out connector and stereo headphones

From: Till (till_k_at_gmx.net)
Date: Thu Jan 29 2004 - 05:42:48 PST


Thanks to Jeff, Peter and David for the input. It seems that I have to
settle on having the Newton´s mono output only on one channel and using
an external adapter which puts it on bot channels. The problem is that
if I wire both contacts in parallel with a bridge, current will also
flow in parallel to the Newton´s internal speaker. So it´s either mono
output on one channel, or mono output on both channels and a speaker
that is not turned off when I plug in the headphones. Too bad...

May want to add a small resistor (4 ohm perhaps) before the
>> jack; you're
>> roughly halving your impedence running two earpieces instead of one.
>
>
> In this case, adding a resistor does nothing but reduce the output.
>
> While it is true that two earpieces in parallel halves the impedance,
> trying to restore the value with a resistor simply
> wastes power in the resistor and reduces the signal available to the
> earpieces.
>
> I say leave it out. The audio out circuit is quite capable of driving
> this load. Headphones don't need much power
> anyway. Even with a big mismatch in impedance there is more than
> enough to drive them.
>
> Unless you are going to amplify the signal, try using higher impedance
> phones (say ~200R).
> They don't load the output too much.

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