Thanks, very helpful.

AC coupling helps me and all I really cared about was that the impedance was greater than 2500 ohms (which is typically where opamp manufacturers quote the max output compared to the rails)

All I am doing is to having an inexpensive stereo mic (designed for camera mounting ) -- the MOVO VXR280 -- feed the Zero soundcard and then have a raspberry PI send the bitstream to another Pi Zero over IP -- this second PI will decode the bits back to audio and feed a Sonos Connect box. The idea is to be able to listen to nature sounds from our river shed (which has wifi) inside the house in Winter when the house is closed up.

I was assuming I will need to use an opamp to bring the microphone output (even though it is labled line I don' t think it actually is) up to the level needed for the sound card.

I have a limited amount of DC at the shed (12 v nominal for a camera) so I was planning on using that with a buck to 5 volt to power the pi and was looking for a rail to rail opamp with virtual ground for the amplifier -- I was assuming I would drive the camera from the raspberry pi zero 3.3v supply and the opamp from either the 5v buck or from a TLE2426 from the 12 volts if I can sort out all the grounds.

On Thu, Jan 21, 2021 at 2:07 PM Matt <matt@audioinjector.net> wrote:

Hi Tom,

The input line impedance varies with input gain. At 0 dB gain, the input impedance is listed as 30 kOhm. At 12 dB gain, the input impedance is listed as 15 kOhm.

The line inputs are AC coupled. If you want to make them DC coupled, then you can short out the two 10 uF capacitors C11 and C12.

What project are you planning on doing ?

Matt

On 22/1/21 3:53 am, Tom Garwin via People wrote:
Sorry if this information is listed somewhere but I have two questions about the stereo line inputs to the Zero board:

1) What is the input impedance?

2) are the inputs AC or DC coupled? In other words is there a blocking/coupling capacitor preventing DC to reaching any on-board amplifier or the A to D chip itself?

Thanks

--

Tom Garwin
-- 
Checkout the community email list :
https://lists.audioinjector.net/mailman/listinfo/people