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iPod/BlackBerry/MP3 input

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rsumperl

rsumperl

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Joined 2009
#1
Hello everyone,
If designing an input for an iPod/BlackBerry/MP3 player, should I use an "R" or a "C" and what value would you think? Everything that I have found online states these players use 32 ohm headsets, thus the 33 ohm resistor, and that the max power out is 30mW. Doing the math, that's around a volt.

Thanks,
Ray
 

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#2
rsumperl said:
Hello everyone,
If designing an input for an iPod/BlackBerry/MP3 player, should I use an "R" or a "C" and what value would you think? Everything that I have found online states these players use 32 ohm headsets, thus the 33 ohm resistor, and that the max power out is 30mW. Doing the math, that's around a volt.

Thanks,
Ray
Click to expand...

For interest you do not need the 33 ohm resistor to "load" the Ipod. What ever has been used at the input is fine. However the output from the H/P socket is not as good as the Ipod connector output. So a charge lead with audio out is better. It does not have a volume control so the input from the Ipod needs to go into a volume control. Many will argue that direct in with no cap is best, however I do like to have cap isolation to something you may hold in your hand. 1uF paper or polyprop works well!🙂

Take a look here:
http://www.diyaudio.com/forums/solid-state/172479-ipod-nano-dock.html


Regards
M. Gregg
 
Last edited:
#4
rsumperl said:
My thought was to have a 3.5mm jack so that I could use a 3.5mm to 3.5mm cable. I thought that would be more "universal" whether I use an iPod/MP3 player or a BlackBerry.
Click to expand...

I have done what you describe, you just need to connect it as any other input only using the 3.5 socket. It works OK. However I wanted to charge the Ipod as well when in use. Forget the H/P load and connect as normal with a 1uF input cap for safety!
You could just use a lead with 3.5mm plug to 2 phono plugs and connect them to any input!<<< I now know this is better because there is no chance of shorting the Ipod H/P out when you connect to the socket, however this is short protected!🙂

Regards

M. Gregg
 
Last edited:
#7
rsumperl said:
I assume the "units" would like to see a load for proper audio response. That's why I thought of the 33 ohm resistor.
Click to expand...

Your looking for maximum voltage transfer rather than maximum power transfer. Putting in a 33 ohm resistor will lose a considerable amount of voltage.

A normal system with a mixer and amplifier has a mixer output impedance of a few ohms while the amplifier will typically have an input impedance of 47K.
 
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