[Elecraft] LINE OUT output too low?

[Matt Zilmer]

FWIW, standard Line Out is 1Vp-p at 600 ohms line impedance.

matt

On Wed, 17 Dec 2008 01:01:51 -0500, you wrote:

>
>
>> Consumer line level ins and outs are designed to handle levels
>> corresonding to a sine wave of at least 1V. 1.4v peak, 2.8v 
>> p-p. 600mV p-p is 13 dB below that. So yes, I agree with the 
>> guy who says that the Line Out level is pretty low. Sorta like 
>> a hot mic level. :) 
>
>Unfortunately, amateur manufacturers have never used the consumer 
>definition of "line level."  Every manufacturer seems to have a 
>different definition for both level and impedance ... from 100 mV 
>at 50K to 4V p-p at 600 Ohms. 
>
>With the AF output mod (47 Ohms in series with the primary of the 
>Line Out transformers), the K3's Line Out looks reasonably clean 
>at 1V or more of audio.  Prior to the change, harmonic distortion 
>got fairly bad above 600 mV p-p. 
>
>The absolute audio level is highly dependent on AGC settings - or 
>the gain reduction caused by AGC action. 
>
>73, 
>
>   ... Joe, W4TV 
> 
>
>
>
>
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net
>> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jim Brown
>> Sent: Tuesday, December 16, 2008 7:25 PM
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] LINE OUT output too low?
>> 
>> 
>> On Tue, 16 Dec 2008 13:16:28 -0800, Lyle Johnson wrote:
>> 
>> >On my K3, with the AFMODKT changes in place on the KIO3 board, and 
>> >driving an open circuit, I get up to 600 mV p-p of audio
>> output if LINE
>> >OUT is set to 100 while listening to a moderately strong signal with
>> AGC
>> >activated.  This of course depends on the signal strength,
>> AGC settings
>> >and so forth.
>> 
>> >A typical output level is less, since the LINE OUT is
>> normally set much
>> >lower than 100.
>> 
>> Consumer line level ins and outs are designed to handle levels
>> corresonding to a sine wave of at least 1V. 1.4v peak, 2.8v 
>> p-p. 600mV 
>> p-p is 13 dB below that. So yes, I agree with the guy who 
>> says that the 
>> Line Out level is pretty low. Sorta like a hot mic level. :) 
>> 
>> Now, audio is dynamic, and except for CW, is almost never a
>> sine wave. 
>> Rather, it's dynamic, with its level varying widely depending on 
>> program. The RMS value of unprocessed (no compression or limiting) 
>> speech and music is typically 14 dB below the peak level. But 
>> think of 
>> it this way -- the audio circuitry has to be able to handle ALL the 
>> voltage in the audio stream, including all the noise and QRM, 
>> and most 
>> of that noise is very "spiky" -- that is, their peaks are 
>> often 20-30 dB 
>> hotter than their average value, and those peaks can clip and create 
>> distortion long before the signal distorts, making the audio a real 
>> mess. Bottom line -- an audio output stage for a 
>> communications RX needs 
>> a lot of headroom. 
>> 
>> 73,
>> 
>> Jim K9YC
>> 
>> 
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