Hi, FWIW I've done this. I've increased the gain by 12 dB, i.e. two bits.
Incidentally, the scaling on CONFIG:LIN OUT is linear - i.e. the output voltage is proportional to the number. So for +12 dB w.r.t. the default I've increased it from 10 to 40. Richard Lamont G4DYA On 06/11/16 16:48, ab2tc wrote: > Hi, > > You make a good point for some digital modes. But you should be able to make > up for most or all of these 3 bits by increasing the LINE OUT as it must > surely be before the codec ADC but probably not before the K3's DSP DAC. > It's a shame that they have to do it this way (back to back DAC/ADC, but > everybody else is doing the same). But by adjusting LINE OUT, the USB audio > interface should be no worse than the audio LINE OUT considering the > nonlinearity of the transformer in that path. > > AB2TC - Knut > > > > Richard Lamont wrote >> On 05/11/16 18:13, ab2tc wrote: >> [ >>>>> 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? >> >>> The audio level seen by, say a recording program on the PC depends on the >>> LINE OUT setting on the K3. I left that as the default, 10, and used the >>> Windows mixer to adjust the level. My audio is now reading approximately >>> -6dB below clipping which is probably a little high, but I have set my >>> AGC >>> SLP to the flattest possible setting (highest number). If you prefer a >>> considerable slope on the AGC curve above threshold, you will need a >>> lower >>> LINE OUT setting. Remember that even when throwing away 3 bits, you still >>> have far more resolution than you can use with an HF receiver. >> >> Consider JT65+JT9. There might be 30 or more signals within a 4 kHz >> band, with widely varying levels. If they're all at the same level, then >> each signal will be about 30 dB below the sum of the signals. If the >> signal you want is 30 dB weaker than the others, then it will be 60 dB >> below the sum. >> >> The data sheet shows the ADC has an SNR of 89 dB and THD+N of 0.01% >> (i.e. -80 dB). >> >> If the sum of the signals is peaking to -22 dBFS true peak, than that >> weak JT65/JT9 signal is going to be at -82 dBFS - close to the ADC noise >> floor. Maybe getting at least some of those three bits back could make >> quite a difference. >> >> >> -- >> Richard Lamont G4DYA >> < > >> [email protected] > >> > >> <snip> > > > > > > -- > View this message in context: > http://elecraft.365791.n2.nabble.com/K3S-USB-audio-questions-tp7623845p7623862.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
