From: Humphreys, David (URB) (david.humphreys_at_honeywell.com)
Date: Wed Jan 28 2004 - 12:02:52 PST
> -----Original Message-----
> From: Peter H. Coffin [mailto:hellsop_at_ninehells.com]
> Sent: Wednesday, January 28, 2004 1:33 PM
> To: newtontalk_at_newtontalk.net
> Subject: Re: [NTLK] nearly OT - audio out connector and stereo
> headphones
> 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.
Regards,
PCBman
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