DSP Support Forum: Message List - Audio Extender with BF-533 EZ-Kit Lite

Re: Audio Extender with BF-533 EZ-Kit Lite

analog@sgaur.hosted.jivesoftware.com — Thu, 02 Jul 2009 05:38:27 GMT

Hi,

Thanks for the response. We have set all DAC volume control registers to zero. We are operating at 48KHz sampling rate, in the data sheet we have checked DAC frequency response for 48Khz. There is no attenuation.

with regards,

sunil

Re: Audio Extender with BF-533 EZ-Kit Lite

analog@sgaur.hosted.jivesoftware.com — Wed, 01 Jul 2009 15:49:51 GMT

Hi Sunil,

Are registers 6-13 (DAC volume control) on the 1938 set to 0 for no attenuation?

Regards,

Gabby

Re: Audio Extender with BF-533 EZ-Kit Lite

analog@sgaur.hosted.jivesoftware.com — Wed, 01 Jul 2009 15:24:18 GMT

Hello Sunil,

Some possible reasons why you may be seeing this:

Looking at the typical performance characteristics (in the datasheets) of both devices, for the DAC and ADC components respectively, there is a varied response depending on what frequency you are trying to pass. I'd bet that if you varied the frequency of the sine wave, you would see varying attenuation levels, based on comparing these basic frequency response plots.
The analog conditioning circuitry on the Audio Ez-extender, both for the DAC output and the ADC input (op-amp and discretes) will definitely have an effect on frequency response. I can't say what the effect is without modeling the circuit, but if modeled, it would be possible to obtain some idea of how this circuitry affects the attenuation of the DAC output and scales the signal to the ADC input.

If you would like more specific information on the converters (AD1938 and ADAV801) I'd recommend you contact Linear Applications Support through their email support system:

https://form.analog.com/Form_Pages/support/standard_linear/contacttechSupport.aspx

Hope this helps.

Regards,

Tom

Audio Extender with BF-533 EZ-Kit Lite

analog@sgaur.hosted.jivesoftware.com — Wed, 01 Jul 2009 13:03:44 GMT

Hi,

We are using Audio extender card with BF-533 Ez-Kit Lite. We are receving digital data through ADAV801 and SPOrt0.

This data is transmitting through AD1938 on Sport1.

We have provided 0-db sine tone as input, Then in the output we have observed -12db difference in amplitue level. When we check in Sport1Tx buffer, we found 0x7FFF000, means no attenuation in the receiver. So, problem can be in ADAV1938.

Anybody is having idea whether AD1938 will provide any attenuation.

with regards,

sunil