Audio output on Circuit board to solve latency?

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W2DLC
Posts: 44
Joined: Tue Apr 04, 2017 1:51 pm

Audio output on Circuit board to solve latency?

Postby W2DLC » Thu Feb 15, 2018 1:55 pm

Is there a point on the RSP1 circuit board to sample analog audio? If there was a way to directly grab audio before it get converted to digital and sent to the USB port, that would solve the latency issues.

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mikexeno
Posts: 88
Joined: Wed Jul 08, 2015 3:18 am

Re: Audio output on Circuit board to solve latency?

Postby mikexeno » Thu Feb 15, 2018 3:01 pm

The RSP's do not have a DAC on the board. I don't think this is going to work.

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Roger
Posts: 106
Joined: Fri Dec 29, 2017 7:59 pm

Re: Audio output on Circuit board to solve latency?

Postby Roger » Thu Feb 15, 2018 6:54 pm

W2DLC wrote:Is there a point on the RSP1 circuit board to sample analog audio? If there was a way to directly grab audio before it get converted to digital and sent to the USB port, that would solve the latency issues.


The RSP does not do any demodulation or generate analog signals. It sends a stream of digitized IF samples to the PC software via the USB interface. The software package that you use (SDRuno, HDSDR, SDR-Console, Cubic SDR etc.) processes the IF samples, displays them on the spectrum/waterfall display and demodulates the desired signal and sends a digital audio stream to the soundcard which uses a D/A to get analog output.

Latency is mainly due to RSP processing time, USB delay, demodulator processing time and soundcard buffering/delay. Some software packages have less latency than others but it is still in the hundreds of milliseconds. A hardware box like the Icom 7300 has much less delay from signal reception to audio output because it uses high performance hardware like an FPGA and dedicated microprocessors.

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IQbert
Posts: 10
Joined: Tue Jan 16, 2018 12:24 am
Location: North TX

Re: Audio output on Circuit board to solve latency?

Postby IQbert » Thu Feb 15, 2018 7:24 pm

W2DLC wrote:Is there a point on the RSP1 circuit board to sample analog audio? If there was a way to directly grab audio before it get converted to digital and sent to the USB port, that would solve the latency issues.


Take a look at this article that RadioUser did in December 2014 about the RSP. In the block diagram, the Tuner IC outputs differential analog I and Q streams which then go to another IC for ADC processing and USB conversion. If you command it to Zero IF, you may be able to tap into the I stream on the board. I have not tried this myself...yet.

http://www.sdrplay.com/radiouserreview.pdf

Report back with your findings!
Last edited by IQbert on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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W2DLC
Posts: 44
Joined: Tue Apr 04, 2017 1:51 pm

Re: Audio output on Circuit board to solve latency?

Postby W2DLC » Fri Feb 16, 2018 12:56 pm

Thank you for the replies! - Dan, W2DLC

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