loudness control

[maylar]

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

[azira]

Well... the easiest thing I can think of is a switchable resistor before the volumn attenuator. Assuming you have enough gain to begin with...

[Bill Fitzpatrick]

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.

[Jan Dupont]

I have found that the controls (Bass lift and Tilt) on the QUAD 34 and 44 preamp works perfect to simulate a loudness function...

[Bill Fitzpatrick]

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!

[Jonathan Bright]

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.

[fab]

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...