Differential to Single mode conversion?

[stevoamm]

Hi Everybody,

Currently developing a PCI host card to host a wireless modem The modem has a differential speaker output and a differential mic input. My problem is that i want to connect these audio ports to their corresponding ports on a PCI sound card in the same system, which has single ended input/outputs. If i do this directly then i will end up grounding one side of each differential pair.
I have thought of using a audio transformer to convert from differential mode to single mode and vice versa. However i am not sure of the circuitry/ components etc
The output speaker differential impedance is 1 Ohm and the mic input differential impedance is 20K.

I would appreciate any help i can get with this.

 

[Nigel Goodwin]

Just use one connection to each and ground. Ignore the second speaker wire, but ground the second mike wire.

 

[stevoamm]

Thanks Nigel.

Just to make sure i understand this correctly -

If i connect the differential speaker output from the wireless module to the single ended mic input on the soundcard - the signal amplitude will be halved,however the signal integrity should remain unchanged?

Does the same apply when i connect the single ended speaker output from the soundcard to the differential microphone input on the wireless module?

 

[Nigel Goodwin]

Thanks Nigel.

Just to make sure i understand this correctly -

If i connect the differential speaker output from the wireless module to the single ended mic input on the soundcard - the signal amplitude will be halved,however the signal integrity should remain unchanged?

Yes.

Does the same apply when i connect the single ended speaker output from the soundcard to the differential microphone input on the wireless module?

Yes, but you must connect the unused input to ground.