Re: Changes to "LO Drive" in AlsaMixer Have No Affect #udrc-ii


Jeremy McDermond <mcdermj@...>
 

On Jul 3, 2017, at 5:00 PM, Kenny Richards <kenny@holenwall.com> wrote:

Bummer.

I have two radios which require much lower levels. I finally got the IC-207 working by dropping the PCM to 24 with the LO at zero. (Which gave me a near prefect deviation of 3 khz on the service monitor)

I'll bug Bryan about a more hardware focused solution.
There’s not much analog there to deal with. If you need more range on PCM, you might be able to combine the default UDRC with the alsa “softvol” control (http://alsa.opensrc.org/How_to_use_softvol_to_control_the_master_volume). You can use softvol to cut the levels of the input samples before they get to the hardware device. That being said, the volume control on the DAC goes down to 63.5dB. That being said, remember that the dynamic range of a 16 bits of ADC is only around 96dB. If you turn things down all the way, you’re only getting around 33dB of dynamic range on there. Anything you add to that in software volume control is going to reduce that further.

Thanks
Kenny

--
Jeremy McDermond (NH6Z)
Xenotropic Systems
mcdermj@xenotropic.com

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