Attenuation Versus Gain - diyAudio
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Old 16th March 2012, 06:37 AM   #1
jsa_ind is offline jsa_ind  United States
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Join Date: May 2005
Location: Orlando
Default Attenuation Versus Gain

Hello,
Could someone please advise at a balanced line signal level source what would the difference be between Attenuation Control & Gain Control?
Also could someone please advise, if both options are possible which would the better of the two options as to preserving the integrity of the original signal.
Any and all advise would be greatly appreciated!
Thanks,
jsa_ind
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Old 16th March 2012, 10:58 AM   #2
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Join Date: Sep 2004
Location: New Zealand
Quote:
Originally Posted by jsa_ind View Post
Hello,
Could someone please advise at a balanced line signal level source what would the difference be between Attenuation Control & Gain Control?
Also could someone please advise, if both options are possible which would the better of the two options as to preserving the integrity of the original signal.
Any and all advise would be greatly appreciated!
Thanks,
jsa_ind
Attenuation control and gain control, at first reading these can be viewed as the same thing, however the word gain invites that amplification may be involved. Are you needing amplification or what is termed a passive volume control ?. Attenuation is progressive subtraction of the original value to a lower value, and can be done with passive circuits usually resistance.

take a look at L pad attenuation for balanced signals often called a U pad , the simplest way to do this is have equal value resistance for hot and cold leading into a variable resistance , now turn that U a quarter turn to the left to visualise. The connecting path between that lead in is a variable resistor usually of 20 thousand ohms or more.

See; Uneeda Audio - Build your own attenuator pads

The best way i know of preserving integrity is to use LDR's Light Dependant resistors which in this simple U pad implementation only needs 2 as the variable part for 1 channel of stereo. Silonex NSL32SR2 is recommended for its low on resistance.

Cheers / Chris


,
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Old 16th March 2012, 12:19 PM   #3
DF96 is offline DF96  England
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Join Date: May 2007
All active input circuits will impose a signal level limit, beyond which clipping or severe distortion will occur. If an input signal may be higher than this then it needs to be attenuated before reaching the active circuit. Too much attenuation will increase noise, so you need to have the right amount.
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Old 16th March 2012, 03:49 PM   #4
BFNY is offline BFNY  United States
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Join Date: May 2004
Location: Saratoga NY
Quote:
Originally Posted by jsa_ind View Post
Hello,
Could someone please advise at a balanced line signal level source what would the difference be between Attenuation Control & Gain Control?
Also could someone please advise, if both options are possible which would the better of the two options as to preserving the integrity of the original signal.
Any and all advise would be greatly appreciated!
Thanks,
jsa_ind
Most common audio preamps and integrated amps use attenuation in front of a fixed gain stage. Why? It's hard to make a variable gain stage amplifier with say 60-80dB of control.
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Old 16th March 2012, 05:50 PM   #5
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Google for the Shure M267 schematic to get ideas how this could be done. E
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