Talk:Automatic gain control

message: Is adaptive gain control the same as automatic gain control? —ShaneCavanaugh 07:03, 8 February 2006 (UTC)
replies: text: Depends on how it adapts I suppose. 'Adaptive' sounds more intelligent to me than automatic. AGC is just designed to keep the output level constant with varying input. What does adaptive do?--Light current 20:24, 8 February 2006 (UTC)
replies: text: Not all AGC systems keep the output level constant. Some compress the dynamic range, i.e. a compressor, where, say a 40 dB range at the input becomes a 20dB range at the output (2:1). Others might do this over some range then limit to a constant level above a certain threshold, like a VOGAD. Perhaps this is the difference.... but I've not heard the term adaptive gain control as a very widely used term. Graham 23:41, 8 February 2006 (UTC)
thread_title:  Adaptive and automatic 

message: I don't see what the current telephone example has to do with automatic gain control. --Abdull 18:41, 2 March 2007 (UTC)
thread_title:  Telephone example 

message: We have to insert natural selection into this article? Seems as though this could also fall under intelligent design- why even have that discussion on this page?  —Preceding unsigned comment added by 141.131.3.22 (talk) 19:31, 13 October 2010 (UTC)
replies: text: I reworded it; I agree there's no reason to invoke evolution here.  Dicklyon (talk) 22:03, 13 October 2010 (UTC)
thread_title:  Biological? Really? 

message: "Vactrol" redirects to "Resistive opto-isolator."  The caption text for the schematic of an AGC circuit featuring a resitive opto-isolator said "...a Vactrol resistive opto-isolator" with "Vactrol" wikilinked.  The only edit I made in the article was to remove the "Vactrol" and wikilink "resistive opto-isolator" instead. My edit was reverted with a comment of "More informative the other way."  Someone please explain to me how using redundant terms and wikilinking to a redirect page is "more informative."
-- Joe (talk) 01:26, 9 May 2013 (UTC)
replies: text: The point of leaving Vactrol is that it's the part used in the image, according to the source; it's also a widely used and widely known device name.  The point of linking Vactrol rather than resistive opto-isolator is that it would be harder to know what Vactrol refers to the other way.  As the linked article  points out, it's a genericized trademark; so probably we should downcase it.  Dicklyon (talk) 02:05, 9 May 2013 (UTC)
thread_title:  Is there a point to mentioning a specific brand name? 

message: Article said: 'By the early 1930s essentially all broadcast receivers included automatic volume control'
I've fixed this as its so plainly wrong
# First a sizeable percentage of the market in the early 30s was homemade receivers, often of the 2 or 3 valve reaction type, few of which featured agc.
# Second, a large %age of radios in the early 30s were 1920s sets, which did not normally feature agc
# Crystal radios, regenerative sets and other such lower cost technology radios formed a large percentage of the radio market in the early 30s, and didn't generally feature agc.
The reference is someone's book in which he says "AM radio receivers incorporating this AVC circuit came into use about 1930, and it has been included in every set since then" which, quite simply, is not true. A look at any collection of early 30s sets soon confirms this. My 1934 set has no agc.
In his book he also says "This was an invention made by Wheeler in 1925, which maintained a constant sound level from a radio receiver while tuning to various broadcasting signals of differing strengths" which again is not true. It is inherent in the design of simple/early AGC that there is output variation with input level variation. (Think about it for a moment, the ouput level controls the gain, yet he proposes constant output level, which implies constant gain, with widely varying input level. Its impossible.) Its only the practice of agcing the last amplifier stage while deriving the agc signal from its input, not output, that brought agc close to the goal of constant output with variable input.
82.31.66.207 (talk) 00:46, 10 October 2013 (UTC)
thread_title:  AGC in the 30s 

message: > AGC is a departure from linearity in AM radio receivers.[3]
no, change in gain does not equal nonlinearity. A key point about agc is that gain is changed without losing linearity. That someone writes something in a book does not make it so :)
> Without AGC, an AM radio would have a linear relationship between the signal amplitude and the sound waveform – the sound amplitude, which correlates with loudness, is proportional to the radio signal amplitude, 
no, its proportional to the change in rf amplitude
82.31.66.207 (talk) 21:57, 10 October 2013 (UTC)
thread_title:  Confusion 

message: >  To produce the least noisy recording, the recording level should be set as high as possible without being so high as to clip or seriously distort the signal.
Not really, its not that simple. Making full use of tape's dynamic range causes hf compression, hence its desirable to avoid doing so.
82.31.66.207 (talk) 07:43, 11 October 2013 (UTC)
thread_title:  More issues