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Old 15th March 2004, 03:54 PM   #1
maylar is offline maylar  United States
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Default loudness control

Anybody have a link for a circuit that implements a loudness compensation switch? My search results showed a bunch of tone control circuits but no loudness buttons.

Thanks
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Old 15th March 2004, 04:41 PM   #2
azira is offline azira  United States
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Well... the easiest thing I can think of is a switchable resistor before the volumn attenuator. Assuming you have enough gain to begin with...
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Old 15th March 2004, 05:14 PM   #3
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The loudness function is most often tied into the volume control via a separate tap.

There are drawbacks to this scheme though as it cannot take into account the amplifier or speaker's sensitivity. If you familiarize yourself with the operation of loudness circuitry you might find a workaround.

Try googling for - loudness control circuit - or something similar.
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Old 15th March 2004, 06:22 PM   #4
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I have found that the controls (Bass lift and Tilt) on the QUAD 34 and 44 preamp works perfect to simulate a loudness function...
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Old 15th March 2004, 06:38 PM   #5
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Yes, the tone controls on many pre-amps would work fine but what a pain in the butt to use.

A good loudness circuit tailored to the amp/speaker sensitivity would be ideal. Better yet, there could be a sensitivity adjustment to make it universal.

A good DIY project!
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Old 15th March 2004, 11:26 PM   #6
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Default loudness control

Probabaly the most useful contibution in this field is to be found in an old copy of "The Journal of the Audio Engineering Society" (JAES). It is a four page article that describes a "loudness control" built around an inverting op-amp with seven passive components and a linear potentiometer. The authors tackle the problems in this area by having both a fixed and a variable breakpoint to the time constants in the bass region and come up with a circuit that follows the Fletcher-Munson contours to within 3db over a 40db range. The full reference is; "Practical Loudness: An active circuit design approach." Arthur L. Newcomb and Richard N. Young. JAES Jan/Feb 1976 Volume 24, No.1. It is easy to miss the article as it wasn't large enough to go in as a feature and you will find it hidden away in the section called "Project Notes/Engineering Briefs". Many of the bigger City/Uni libraries hold large sets of the JAES but if you can't reach one of these The Societie's reprint service is very efficient. Unfortunately I haven't got their their contact details. They're in New York I believe. Another member may be able to post the details. Jonathan Bright.
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Old 28th March 2004, 04:12 AM   #7
fab is offline fab  Canada
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Default Loudness

This variable loudness is not a traditional loudness since the Loudness effect does not vary with volume setting control.

The pre-amp circuit includes a gain 5.7 without the loudness. When the switch is in OFF position, the pre-amp still give low sub-audio frequency a pre-emphasis allowing the phase shift at 10 Hz to be lower than 0.5 deg, thus the 10 Hz square wave is almost perfect.

I am very pleased with the result. If anyone has tried something similar or would like to comment...
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File Type: gif pre-amp_loudness_1.gif (10.0 KB, 859 views)
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Old 21st July 2012, 09:51 PM   #8
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Lightbulb Loudness control circuit

Hi guys!
Here schematic for quality loudness control, but do not know the value of the components of a schematics?
If anyone has knowledge of value let them write here.
thank you!
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File Type: doc Loudness-Schematic-1.doc (36.0 KB, 163 views)
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Old 21st July 2012, 11:29 PM   #9
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There are other threads which may be useful:
Reverse of the old Loudness Control
Volume Control with Loudness and no Taps
ACTIVE loudness control
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Old 22nd July 2012, 12:03 AM   #10
fab is offline fab  Canada
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if you want something w/o adding any active circuit in series in your existing system, use the circuit in post #7 where the loudness is included in your actual pre-amp (in the feedback path of your pre-amp, provided that is is a non-inverting one). You simply have to modify your pre-amp but ensure to put the potentiometer close to the pre-amo circuit to prevent capturing too much noise, thus locate the pre-amp circuit close to your pre-amp front panel where the pot is located...
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