Just something about a DC coupled amp.
Ok,
I've been through my back issues of Silicon Chip.
The July 1996 issue has a 3-band parametric equaliser. It's a very basic circuit, all 3 bands are standard boost/cut variable Q (bandpass). It wouldn't be very suitable for loudness compensation, where we require a relatively shallow LF boost and then a sharper cut for excursion control.
But as I was putting the magazines back on the shelf, I glanced at the cover of the December 1997 issue. "Loudness control for car hi-fi." It appears to be intended to do almost exactly what I have in mind. I'll summarise the article later.
I've been through my back issues of Silicon Chip.
The July 1996 issue has a 3-band parametric equaliser. It's a very basic circuit, all 3 bands are standard boost/cut variable Q (bandpass). It wouldn't be very suitable for loudness compensation, where we require a relatively shallow LF boost and then a sharper cut for excursion control.
But as I was putting the magazines back on the shelf, I glanced at the cover of the December 1997 issue. "Loudness control for car hi-fi." It appears to be intended to do almost exactly what I have in mind. I'll summarise the article later.
Have a look , if my memory serves me well, at the 4th section. The parametric was three stage as you said, there was a fourth stage.
Terry
Nope, definitely just 3 bandpass stages. But like you, I'm sure I've seen a circuit for a parametric with a shelving filter at the LF end somewhere.
I'll take a look through the yearly indexes and see if there were any others.
According to the SC Web site, there was a subwoofer controller with parametric EQ in the December 1995 issue. It was updated in 2007:
Silicon Chip Online - Subwoofer Controller
Maybe that was it?
I've now looked at the loudness control from the December 1997 issue.
It's not suitable. The LF boost starts too far up the frequency range, and the amount of boost actually starts to reduce again as the volume setting nears minimum. It also boosts the treble as well as the bass, which I have always found unnatural. The response curves were apparently arrived at by experiment, which likely means the curves were chosen to suit a typical car stereo rather than a home environment.
See http://www.diyaudio.com/forums/subwoofers/153359-reading-driver-displacement-radar.html
Why not monitor actual displacement and use that as a key to limit input signal to the LF driver? No preamp mods required.
Sorry to revive this old thread, but I found this while doing a search for "subsonic filters".
Isn't the above exactly what Yamaha was doing with their older recievers and amps from the 70's and 80's? They all had the variable loudness control that worked in conjunction with the volume control. One could simply download an old Yammy schematic and copy their loudness technique.
I recall the Yamaha's with the variable loudness controls, but I don't think they were tied to the volume.
The Chase that I mentioned previously, did just that.
cheers,
AJ
I tried this out last night and it seems to work. It works for increasing and decreasing and the first volume is for calibration.
An externally hosted image should be here but it was not working when we last tested it.
Those curves don't look right. See http://www.diyaudio.com/forums/solid-state/154209-reverse-old-loudness-control-3.html#post1975429
Best, Markus
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.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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
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
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.
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.
Well, there's Dolby Volume. I'm currently evaluating its functionality and will have some measurements soon.
Best, Markus
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.
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.
Last edited:
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
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
6 Gang pots for Don Hills. Are they what you need for this project?
http://www.bitechnologies.com/pdfs/p260.pdf
I found this today if it is of any use.
jamikl
http://www.bitechnologies.com/pdfs/p260.pdf
I found this today if it is of any use.
jamikl
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.