In the December 2023 of AudioXPress Doug Self has a great article on tone controls. The controls that he describes are peaking controls rather than shelving controls like what he described in Jan Didden's Linear Audio #5. The new tone controls are much simpler in design than those in LA #5 and they sound great! Soon after buying the December issue of AudioXPress I read Doug's article and built the described pair of tone controls. I then wired them in place of the LA #5 controls that are part of this Doug Self Preamplifier and I really liked them! I found them to be a bit more musical and easier to tune than the LA #5 tone control. More than anything I suspect that what I am hearing is my personal preference for peaking rather than shelving filters. Peaking type filters are common in studio recording consoles and pro gear.
The intent of this thread is to not only explore the need and implementation of tone controls but loudness controls as well. What is the best way implement a loudness control? I personally think that one that tracks with the volume control would be a good idea. Less than that I would settle for one that changes EQ dependent upon turning a 'loudness pot' much like a volume control. Doug offers up a good tutorial on loudness controls in his book 'Small Signal Audio Design', 3rd edition. the Loudness tutorial start at page 373
I want to hear any and all thoughts on the topic as well as posting your favorite circuit for doing tone controls and/ or loudness. Let's make this a monster thread demonstrating many ideas while respecting one another's opinions. I've asked Doug to join us as well.
The intent of this thread is to not only explore the need and implementation of tone controls but loudness controls as well. What is the best way implement a loudness control? I personally think that one that tracks with the volume control would be a good idea. Less than that I would settle for one that changes EQ dependent upon turning a 'loudness pot' much like a volume control. Doug offers up a good tutorial on loudness controls in his book 'Small Signal Audio Design', 3rd edition. the Loudness tutorial start at page 373
I want to hear any and all thoughts on the topic as well as posting your favorite circuit for doing tone controls and/ or loudness. Let's make this a monster thread demonstrating many ideas while respecting one another's opinions. I've asked Doug to join us as well.
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Hi Carl,
I have quite a few bare bones DIY preamp such as a Pass BA-3, BA2018, Aikido as a few examples that only feature a volume control. I am always interested in a quality tone and balance board that would be easy to integrate that would improve the flexibility of these excellent sounding designs.
I have quite a few bare bones DIY preamp such as a Pass BA-3, BA2018, Aikido as a few examples that only feature a volume control. I am always interested in a quality tone and balance board that would be easy to integrate that would improve the flexibility of these excellent sounding designs.
Hello all.
I should say that in 'Small Signal Audio Design', 3rd edition. the Loudness stuff starts at page 373, not page 750.
I conclude there that the reason that 1970s loudness controls were unpopular is that they gave an unnecessary HF boost, due to a misreading of the Fletcher & Munson curves. This would have accentuated the high-frequency distortion fron vinyl.
In the 2nd edition of SSAD there is a shorter version that starts at page 382.
I should say that in 'Small Signal Audio Design', 3rd edition. the Loudness stuff starts at page 373, not page 750.
I conclude there that the reason that 1970s loudness controls were unpopular is that they gave an unnecessary HF boost, due to a misreading of the Fletcher & Munson curves. This would have accentuated the high-frequency distortion fron vinyl.
In the 2nd edition of SSAD there is a shorter version that starts at page 382.
I'd be interested to see some various methods of loudness control. The most promising one I know from the top of my head is the Newcomb & Young circuit (JAES 1976) which does NOT give HF boost. Unfortunately as it stands it has some problems with noise gain. It's in 'Small Signal Audio Design', 3rd edition, page 377 onwards.
My old Sansui A60 had variable loudness, anything over 2 just made it sound rather muddy. But for quiet listening a boost to maybe 0.5 was good. (At least I thought so at the time). I’m fairly sure that control also gave HF boost along with the bass lift.
So variable loudness gets my vote too!
So variable loudness gets my vote too!
What is your impression of Yamaha gear that makes use of lowering the midrange only instead of boosting bass and treble?
I assume you mean the usual tapped-volume-control configuration, also used by Denon, Pioneer, Sansui, and just about everybody else. If so, that does give the unwanted HF boost. You only need LF boost.
I assume you mean the usual tapped-volume-control configuration, also used by Denon, Pioneer, Sansui, and just about everybody else. If so, that does give the unwanted HF boost. You only need LF boost.
Excellent! Very natural sounding and precisely tunable.
And safer for the speakers. And does not need a bypass switch: just turn the loudness pot to it's min end - the extra components get short-circuited
The general idea lies in post #10 (and #21) below, but do read the whole thread :
https://www.diyaudio.com/community/threads/loudness-stage.202413/
It gives very little HF boost compared to the LF boost, just as it should. You can see the curves in the post#10 I mentioned above.
All in all, an extremely VFM, simple and effective little circuit.
Thats a really good masking unity gain input buffer stage RickRay input noise has no chance. The active tone control second stage buffer is also very interesting but could be improved by using jfets in the LTP they really aim for low THD at this stage. The loudness control is adjustable.
What Huff loves is the ability to dial into some specific frequency range say 3k or the 100-200Hz region and cutting this. Peaking filters are great for cutting but poor in boosting notch areas. If you have two peaking filters with adjustable frequency and Q you can use one as a bass boost or use it to cut problem room midbass bloom and the other to cut a notch in the 3k region or adjust the 1k tone.
Shelving filters can handle notches better by boosting the neighboring frequencies slightly covering up the notch. These tone controls were designed with RIAA and Fletcher Munson curves in mind and are thus some how centered around 500 to 1k, they dont work great in real life. In real life speakers loose bass and thus the bass boost was born but with a very steep highpass filter around 20Hz less the driver die.
Modern tone controls feature both shelving filters and at the frequency extremes and adjustable peaking filters at the 100-300hz and 1k-3k regions to address various concerns, the shelving low frequency tone control is sometimes replaces with an additional peaking filter or bass boost but with steep highpass filter. In real life normal tone controls hardly work.
Theres no easy way to implement what Huff is suggesting apart from using calibrated presets that are triggered with volume level. This might be a big thread.
What Huff loves is the ability to dial into some specific frequency range say 3k or the 100-200Hz region and cutting this. Peaking filters are great for cutting but poor in boosting notch areas. If you have two peaking filters with adjustable frequency and Q you can use one as a bass boost or use it to cut problem room midbass bloom and the other to cut a notch in the 3k region or adjust the 1k tone.
Shelving filters can handle notches better by boosting the neighboring frequencies slightly covering up the notch. These tone controls were designed with RIAA and Fletcher Munson curves in mind and are thus some how centered around 500 to 1k, they dont work great in real life. In real life speakers loose bass and thus the bass boost was born but with a very steep highpass filter around 20Hz less the driver die.
Modern tone controls feature both shelving filters and at the frequency extremes and adjustable peaking filters at the 100-300hz and 1k-3k regions to address various concerns, the shelving low frequency tone control is sometimes replaces with an additional peaking filter or bass boost but with steep highpass filter. In real life normal tone controls hardly work.
Theres no easy way to implement what Huff is suggesting apart from using calibrated presets that are triggered with volume level. This might be a big thread.
Here's the cute preamp that kicked off the new slopes revolution over 10 years ago that you can now find even in your Marantz n30/40 https://www.pcbway.com/project/shareproject/Preamplifier_490de946.html
Another item that affected traditional tone controls is tape noise and many of these did partly try to implement dolby nr slopes
Another item that affected traditional tone controls is tape noise and many of these did partly try to implement dolby nr slopes
Almost the first thing I did when this thread appeared was look up the Nakimichi 630, because I remembered its enigmatic 'Contour' control. According to the user manual it "Provides high and low frequency compensation for low listening levels.."
It seems to operate in much same way the usual centre-tapped-pot loudness control, but is configured rather differently. Two back-to-back electrolytics form the LF time constant, which I think rather iffy for distortion.
It seems to operate in much same way the usual centre-tapped-pot loudness control, but is configured rather differently. Two back-to-back electrolytics form the LF time constant, which I think rather iffy for distortion.
From the 630 user manual:
CONTOUR
The normal position of this control is fully clockwise.... To use the contour control, first turn it fully clockwise. Turn up the volume control to normal maximum listening levels. Then turn the listening level down with the contour control instead of the volume control. loudness compensation will take place automatically.
So, two controls, as suggested by Adason.
CONTOUR
The normal position of this control is fully clockwise.... To use the contour control, first turn it fully clockwise. Turn up the volume control to normal maximum listening levels. Then turn the listening level down with the contour control instead of the volume control. loudness compensation will take place automatically.
So, two controls, as suggested by Adason.