(USB) Audio device with 5LP

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RaAl_264636
Level 6
Level 6
50 sign-ins 25 sign-ins 10 solutions authored

Hi,

I want to realize a small audio application, which should have an audio output and alternatively be able to work as an USB audio input. Two questions:

1) For the audio output, I assume that the line-in voltage of a audio device is typically about 0.775V. Is this correct? So, if I'm using an IDAC with 2mA setting and a 380 Ohm resistor, I'll get about 0.76V. Using an OpAmp in FollowerMode to achieve high current output, I can connect the PSoC5LP directly to a line-in input or drive a headphone with at least 32 Ohm impedance (0.76V divided by 25mA OpAmp output current results in ~30 Ohm) without damaging the device?

2) Anyone has experience with setting up an USB component for USB Audio input? It seems that there's a template for audio input application for the USB decriptors, but I don't know if I can use it directly without modification. Unfortunately there's no example firmware for USB input, only an output example is provided.

Regards

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1 Solution
5 Replies

Hello Anks,

thank you for those links. I'll check if I can get information about the USB audio input part out of it.


Any hints about using a headphone with only the internal OpAmp?

Regards

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about using a headphone with only the internal OpAmp  a little discussed here:

audio streaming using usb

and It seems nobody succeeded in transfer the project https: //www.element14.com/ ...

to the new version of PSoC Creator ((

Check this app note by Linear Technology on driving headphones,

Solutions - LTC6261 Audio Headphones Bridge Driver

/odissey1

RaAl_264636
Level 6
Level 6
50 sign-ins 25 sign-ins 10 solutions authored

Hello,

my apologies for the late reply. Here's an update about the headphone circuit:

currently I'm using the iDAC as a signal generator, current strength is 2mA. Resistor value is choosen so that the maximum voltage is about 0.78V (390 Ohm), so there's a peak voltage of 0.39V. This voltage is connected to two internal OpAmps (for left/right channel) in follower mode and then output to OpAmp output pins. A 100µF series capacitor for each channel is connected between output pin and headphone connector to eliminate DC part of the signal.

This seems to work in general, I'm using 32 Ohm headphones and a sinus test signal with 1kHz (512 samples).

Regards

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