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Re: Topband: [Bulk] Re: ADC Overload from MW transmitters

To: topband@contesting.com
Subject: Re: Topband: [Bulk] Re: ADC Overload from MW transmitters
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sat, 24 Oct 2015 15:49:13 -0700
List-post: <topband@contesting.com">mailto:topband@contesting.com>
On Sat,10/24/2015 3:02 PM, Stephen Hicks, N5AC wrote:
Simply my opinion here, but in my experience booth analog and digital can
yield results that will please even the most discerning audiophile.

In the world of pro audio (those who make a living doing it) we say "audiophool," alternate spelling "audiofool."

Generally, the things that go wrong are design errors that result in
distortion.

Or a system that has inadequate headroom.

It's important to understand that devices operating in the digital domain produce different KINDS of distortion than do devices in the analog domain. Clip in the analog domain is usually a gradual transition from linear behavior; the distortion products are intermod and harmonics. Intermod and harmonics are also present in nature -- most real objects that vibrate produce harmonics, and many produce intermod. The human voice and most musical instruments all fall into this category. As a result, the ear/brain views low order harmonics and intermod of audio frequencies as far more "natural" than higher order harmonics and intermod. ANY well-played instrument includes harmonics of the fundamental note being played -- it is PART of the instrument's natural sound. There are, for example, musical "sound effects" units that intentionally produce second harmonic distortion of the input signal. The front panel control that sets the strength of the 2nd harmonic is called "warmth."

By contrast, clipping (overload) distortion in the digital domain is all of the digital bits at 1, which produces a high strength impulse (click) at the transition, no signal until the level drops below clip, and another click at the transition. At the low signal end of an A/D converter, there are not enough bits to accurately describe the signal, so the digital signal produced is a poor copy of the analog signal. Digital distortions are NEVER natural, so are, in general, far more perceptible by the ear/brain than analog distortions.

73, Jim K9YC
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