Reverse of the old Loudness Control

[markus76]

Originally Posted by AJinFLA

Those curves don't look right. See Reverse of the old Loudness Control

Best, Markus

[Artie]

Originally Posted by AJinFLA

I recall the Yamaha's with the variable loudness controls, but I don't think they were tied to the volume.

Yup. You're correct AJ. Just checked a schematic.

[Key]

Typo that first one is the wrong signal flow. This is what I was using. The bass roll off isn't much on the upswing so changing the xover to around 300-500Hz on the inverted filter would maybe work better for that application.

[jamikl]

Unfortunately I've been away from the forum for awhile, and been laid off as well. Has there been an actual circuit made available yet or is it still work in progress. I am still interested in what Don Hills was proposing.

I once had one of the J. L. Hood 75 Watt amps as published in Hi Fi News 1971, I think. This may have had a loudness control that varied with volume. I know it had variable tone controls. The amp and the manuals are unfortunately in New Zealand so I can't check if this was so.

jamikl

[Don Hills]

No material progress yet. I'm still looking for a suitable (and inexpensive) IC gain control chip, or the parts to make a 3-pot mechanically ganged unit for a prototype. Unfortunately I junked a heap of old valve radio chassis a few years back, I could have used the dial cord drums if I could have found 3 the same diameter. (Tuning capacitors often had the same diameter shaft as potentiometers.)

As for the JLH amp, I have the HFN&RR articles for the 75 watt direct coupled amp. It was published November 1972 through early 1973. The preamp has:
- A steep slope HP (rumble) filter with adjustable cutoff frequency.
- A variable slope HP (scratch) filter.
- Bass and treble controls with adjustable "knee" frequencies.

But there is no "loudness" control or circuitry.

[markus76]

Originally Posted by Don Hills

But there is no "loudness" control or circuitry.

Well, there's Dolby Volume. I'm currently evaluating its functionality and will have some measurements soon.

Best, Markus

[bentoronto]

In post #10 in a thread in subwoofers, I introduce some core puzzles related to the equal loudness compensation that seem to be overlooked.


BTW, piece of cake to get a pre-amp (or vintage pre-amp) loudness correction to satisfy your ear when you are multi-amped. Just crank down the amp volume controls and crank up the pre-amp volume... till your pre-amp volume control typically is way higher than you ever used before (that will also help pre-amp S/N output). Can also be managed using the versatile "external processor loop" jacks or even by working creatively with a tape-out/tape-in circuit.

[markus76]

This reminds me that I wanted to post some Dolby Volume curves. Well, I struggled with a ill-conceived AVR the past few months and now I'm waiting for a Onkyo TX-NR708 to arrive. But the Onkyo has Audyssey Dynamic EQ, the equivalent to Dolby Volume, so let's look at that technology.

What I found so far is that the equal-loudness contours of ISO 226:2003 don't match those of Dynamic EQ nor those of Dolby Volume. Someone suggested that the equal-loudness contours might look different when signals different from pure tones are used. Has anybody more detailed information on that?

Best, Markus

[jamikl]

http://www.bitechnologies.com/pdfs/p260.pdf
I found this today if it is of any use.
jamikl

[markus76]

Originally Posted by jamikl

http://www.bitechnologies.com/pdfs/p260.pdf
I found this today if it is of any use.
jamikl

Solutions with a fixed compensation curve will ultimately fail because the curves need to be dynamically applied depending on the actual program loudness. This requires digital signal processing.