Loudness Control.

[ronchinoy]

My old Akai amp from 1979 had a button called Loudness and one called Tone.
Can somebody explain what these two buttons did. ?. i.e. what freq ranges were boosted ?.
And how I could add such a circuit to my pre amp or AMP.
Pre Amp is a DIY NE5532 job and AMP is a DIY TDA7294
Circuit of my Preamp / Tone control board included.
Sorry for the Noob questions. Im just getting started in this as a hobby.
Worst case I plan to find the schematic of the old Akai amp and study how they did it.

 

[TwentyTrees]

Welcome to GDIY! This is a tricky one, it would certainly help to see the schematic of your Akai amp - that's the best way to start I'd imagine. I don't know any good hifi schematic repositories, though others might?

 

[Tubetec]

Loudness applies a lift in the LF range at lower positions of the volume control . See Fletcher-Munson curve.
Most likely a Tone switch bypasses the treble and bass controls .

 

[vintagelove]

Maybe a little OT, but I rebuilt an old tube radio into an octal champ kind of thing. Anyway, it had one of those 4 tab volume knobs because it originally had a loudness control. I hooked it up and it sounded really good. Here’s the schematic, see the output transformer running back to the volume pot.

 

[Script]

The Yamaha PM170/180 mixers have a RLC filter fixed at 90Hz or 100Hz or so. It's a bass tone control at a typical 'loudness' frequency. They use a "patented" (cough!) inductor, but any inductor should do.

 

[ronchinoy]

This is the best I could find so far.
https://www.tubecad.com/2021/08/blo...NsWYzM5Rw6H6rzaFcuIBsA4oPUFt1Mo3UT-k3_yOb0SWE

 

[MisterCMRR]

Patented inductor indeed!! Everything old becomes new as they say. A really high-performance loudness control appeared in the 1964 General Electric (GE) Transistor Manual. Note that, with volume set at -40 dB, some 30 dB of boost is available at 30 Hz. Instead of a loudness switch, a pot controls the amount of compensation. C10 and the inductor cleverly form a series resonant circuit, so the slope of the rise is steeper than any simple R-C circuit and midrange response isn't muddied up since boost at 500 Hz is only a couple dB. A bit of very clever engineering I'd say. In 1964, I was learning everything I could about transistors and working in a 10-man TV repair shop. I was the only one who understood transistors when they started appearing along with tubes in TV sets of the day and "transistor" pocket radios were the rage!

 

[Gus]

The 64 transistor manual is a good book to own.
I bought my copy in 76.