[Xylo-SDR] Janus board connectors

["Phil Harman" <pvharman@arach.net.au>]

[Background - the Janus board is a high performance A/D and D/A converter 
that connects to the PC via USB.  It will provide full duplex operation at 
up to 192k samples per second at 24 bits.  The hardware is based on an FX2 
USB interface feeding an FPGA and high performance A/D and D/A converters. 
The FPGA will also be used in conjunction with a  GPS  1pps clock, or 
stabilized oscillator, to enable any frequency error and drift of the 200MHz 
DDS clock to be corrected within the PowerSDR software. The hardware and 
software for the project is being developed by Bill KD5TFD and Phil VK6APH 
and will be open source.]



We have now successfully tested the TLV320AIC23B as a microphone amplifier 
and  Audio out/Headphone amplifier for the Janus  USB high speed  A/D and 
D/A board.



We need to decide what connectors we want on the edge of the board and how 
many.



The latest block diagram is here:



< http://www.hamsdr.com/dnld.aspx?id=139 >



Since the board is 100mm (~4") wide then we are a little tight for space.



I suggest  3.5mm jack sockets for the microphone and headphones.  A bias 
voltage is available for Electret  microphones.



I also suggest using  3.5mm stereo jacks for the high speed  A/D inputs. 
Since all the A/Ds we are considering can take a balanced input a stereo 
plug will provide a  balanced input and  a mono plug will earth one input 
for use with unbalanced inputs. This does mean that we will need two leads 
from the radio as apposed to the single stereo jack at present.



We can either use 3.5mm jacks for the remainder of the sockets or consider 
RCA's.



Is it worth going to gold plated RCA sockets - what experience do the 
audiophiles have with these?



Some of the options are:



 1.. Don't mount the connectors on the PCB but use a breakout box like the 
D44
 2.. Don't provide balanced inputs for the  high speed A/D converter
 3.. Don't fit line in on the Tx  A/D - do we need this for digital modes 
now we have VAC?
 4.. Don't fit line out, use the headphone out to drive external speakers 
etc
 5.. Use stacked RCA sockets -  but that will increase the height of the 
board
 6.. Use smaller alternatives to RCA sockets  - DIN perhaps?
At the moment my preference is to use 3.5mm jacks for all connectors.



Comments and suggestions welcome.



73's  Phil.VK6APH



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