[hpsdr] Question: Line out audio vs earphone audio

[Phil Harman]

Hi Ron,

The TLV320 DAC we use in Mercury,  Penny and Janus would support this - just 
a matter of sending the required volume in the Command & Control packets.
Let's put in on the list for future enhancements.

73's Phil... VK6APH


----- Original Message ----- 
From: "Ronald Cox" <w9kfb1 at mac.com>
To: <hpsdr at hpsdr.org>
Sent: Thursday, January 15, 2009 1:52 PM
Subject: [hpsdr] Question: Line out audio vs earphone audio


> ***** High Performance Software Defined Radio Discussion List *****
>
> From Wikipedia:
> "Line out
>
> The signal out of line out remains at a constant level, regardless of
> the current setting of the volume control. You can connect recording
> equipment to line out and record the signal, without having to listen
> to it through the device's speaker, and without the loudness of the
> recording changing if you change the volume control setting of the
> device while you are recording.
>
> The impedance is around 100 ohms, the voltage can reach 2 volts peak-
> to-peak with levels referenced to -10 dBV (300 mV) at 10k ohms, and
> frequency response of most modern equipment is advertised as
> 20Hz-20kHz (although other factors influence frequency response).
> [citation needed] This impedance level is much higher than the usual 4
> or 8 ohms of a speaker, such that a speaker connected to line out
> essentially short circuits the op-amp. Even if the impedances would
> match, yielding the theoretical maximum power transfer of 50%, the
> power supplied through line out is not enough to drive a speaker."
>
> Is there a place to get such a signal so digital modes can operate
> unaffected by the AF control on PowerSDR with Mercury. Maybe it is in
> the plan for the future?
>
> Ron, W9KFB
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