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WebWilly 13th December 2011 10:35 AM

Loudness stage
Hi all.
I'd like to build a simple "loudness" stage for include beetwen TV low level output and the line input in my amplifier.
I'm thinking in a operational step like LM387 or so. But I have not idea about RC filters.
I need to have a single +V for the circuit (if is +5V, better).
Thanks for your help

Mooly 14th December 2011 07:34 AM

"Loudness" stage often means a modified frequency response such as the old "loudness" control that was always fitted to 1970/80's music centres and amplifiers.

Or do you mean a preamplifier ? to just boost the signal level.

WebWilly 14th December 2011 07:54 AM

Thanks Mooly.
I mean the old "loudness" control you refered. The aim is to listen the TV in very low sound level in the room but with confortable feeling. I know that this is not purity sound, because some tones will be modify.

Mooly 14th December 2011 01:01 PM

Haven't anything I can think of to recommend tbh. A proper loudness control uses a tapped volume control.

This was an odd design with limitations but might achieve what you are after at a fixed level,

PRR 15th December 2011 12:56 AM

> in very low sound level in the room but with comfortable feeling.

WebWilly 15th December 2011 06:50 AM

Many tanks Mooly and PRR. I'll try with this and let you know the result.

PRR: tha capacitor is 0.03 uF if I read correctely, isn't ?


mjf 15th December 2011 06:06 PM

1 Attachment(s)
..........examples from an old hifi - book

tiefbassuebertr 5th March 2012 11:44 AM

Real time Loudness Meter
1 Attachment(s)
check out this URL:
Grimm Audio

The Luxman Receiver R5030 uses a variable loudness filter - go to page 15 about sm from
Luxman R-5030 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine

formula 22 28th July 2012 04:25 AM

Hi guys!
You can offer a schematic or project for the active filter for loudness control.
thank you!

rcw666 7th August 2012 05:47 PM

This is a passive loudness circuit that can be put on the end of a pre amp...

The effect as you turn the pot over full rotation is...

The 33k resistor is just to simulate a typical load and is not needed it will drive a following circuit over about a 20-100k range withought very much change in the frequency response.

The component values can be scaled to for instance use the 10k motorised pot widely available here in Oz. In this case just double all resistors and halve capacitors.

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