[Elecraft] K3S USB audio questions

[Matt Zilmer]

Hi Richard,

Some answers, below.  --matt


On 11/5/2016 9:38 AM, Richard Lamont wrote:
> A few questions about the K3S internal audio interface:
>
> 1. Is the internal connection between the USB audio interface and the
> 2nd IF analogue or digital? If digital, how is the sample rate
> conversion implemented?

The KIO3B uses a codec (digital on its USB side, analog one the audio 
side (line in/out).  The codec's USB D+/- nets are connected to a USB hub.


>
> 2. It seems to support sampling rates of 32000, 44100 and 48000 Hz, but
> not higher or lower values. Is this correct?

These are the sample rates the codec supports.  Yes.

>
> 3. What determines the clock frequency for this sampling? Is it a
> free-running crystal? If so, what is its frequency tolerance? Or is it
> locked to the main TXCO and/or external 10 MHz reference?

The clock is an XO: 12 MHz, +/- 100 ppm as rated.  The XO's output is 
buffered and feeds the codec.

>
> 4. When listening to SSB audio at S9+, with slow AGC, the output level
> via this interface seems to be -22 dBFS true peak. Why is it throwing
> away three bits of resolution? Or is this amount of headroom
> necessary/useful?

You can find a copy of the data sheet here: 
http://www.digikey.com/product-search/en?keywords=PCM2901E%2F2K

73,
matt W6NIA

>
> TIA.
>

-- 
Always store beer in a dark place.  - R. Heinlein

Matt Zilmer, W6NIA
[Shiraz]