No - conclusion is totally wrong.
- Loudness circuit is a good thing to have - it's there not for cheating, but for compensating the human year's change in frequency response curve at low volumes.
- Most of the higher-level Telefunken amplifiers and receivers provide ability to switch the loudness circuit off.
So my conclusion is wrong, the bass and treble isn't boosted to sell the amp by making it sound more clean and authoritative,
the Right conclusion is : not for cheating but for compensating the human ear* change in frequency response curve at low volumes!
further: I hope many diy people will incorporate such circuits in their diy amps which sound uneven at low volumes.
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I'm still not sure you understand the function of "loudness" circuit correctly.
First picture attached shows the frequency response curves at different volume levels, corresponding to equal listening perception throughout the audio bandwidth.
Second picture shows the way one of Yamaha amplifiers loudness circuit approximates those curves (I don't have such a picture for Telefunken, but the principle is exactly the same).
So, if you measure your Telefunken at the maximum volume pot position - will you be surprised? - it will be rather flat. The lower the volume pot position, the higher correction you see at the lower and higher ends of the audio bandwidth (lower end correction is always more aggressive). You can build the graph - similar to Yamaha's one - yourself, measuring the frequency response at different volume pot positions (using external linear pot for keeping the constant signal levels for measurement system).
No cheating. Just making it sounding the right way.
Attachments
Of course, in order for a variable loudness contour to work effectively, the system gain must be adjusted separately in an attempt to match the varying curve to the proper SPL in the room at various volume control settings.
When I was a kid, I added a level adjust pot between the preamp & power amp sections of my Heathkit integrated amp for just this purpose, since it normally had "too much gain," and always applied too much loudness comp when the button was pushed. By reducing the gain (and increasing the volume slider position), I was able to adjust things until the compensation was at minimum for "normal" (louder) listening, then applied more accurately at lower levels. Didn't use an SPL meter or anything, just set it by ear. This actually worked quite well, and I pretty much left the loudness button on after that.
I only ever saw one commercial product (a large, '70s-era Kenwood receiver) that actually recognized & addressed this issue. It had a regular volume knob with the usual selectable/ variable loudness comp, but also a concentric ring knob for calibrating the system gain. Pretty cool, I thought at the time.
Of course, my modern rig has no loudness comp at all, and I don't really miss it. I've wondered why that is, and the only thing I can come up with is that the output of my current system is so much smoother and more extended at both ends than my '70s setup ever was, it just doesn't seem to "go away" as much at lower listening levels? I dunno... 🙄
-- Jim
When I was a kid, I added a level adjust pot between the preamp & power amp sections of my Heathkit integrated amp for just this purpose, since it normally had "too much gain," and always applied too much loudness comp when the button was pushed. By reducing the gain (and increasing the volume slider position), I was able to adjust things until the compensation was at minimum for "normal" (louder) listening, then applied more accurately at lower levels. Didn't use an SPL meter or anything, just set it by ear. This actually worked quite well, and I pretty much left the loudness button on after that.
I only ever saw one commercial product (a large, '70s-era Kenwood receiver) that actually recognized & addressed this issue. It had a regular volume knob with the usual selectable/ variable loudness comp, but also a concentric ring knob for calibrating the system gain. Pretty cool, I thought at the time.
Of course, my modern rig has no loudness comp at all, and I don't really miss it. I've wondered why that is, and the only thing I can come up with is that the output of my current system is so much smoother and more extended at both ends than my '70s setup ever was, it just doesn't seem to "go away" as much at lower listening levels? I dunno... 🙄
-- Jim
Sure, this kind of approach provides limited accuracy and requires volume calibration, as you just mentioned. Many experienced listeners nowadays prefer listening at normal (relatively high) volumes - in this case "loudness" correction is not required, causing more problems, than advantages.
However, for many consumer users, listening the music in the background at low levels, "loudness" gave (and still gives) a better listening experience. Sure, it's good to be able to bypass it for listening at normar levels.
Again - no cheating, just an attempt to improve the listening experience at low volumes.
BTW, many modern digital processors have got a digital implementation of "loudness" correction with ability to switch it on/off.
However, for many consumer users, listening the music in the background at low levels, "loudness" gave (and still gives) a better listening experience. Sure, it's good to be able to bypass it for listening at normar levels.
Again - no cheating, just an attempt to improve the listening experience at low volumes.
BTW, many modern digital processors have got a digital implementation of "loudness" correction with ability to switch it on/off.
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There is a fix loudness network around the vol pot.
Turn on the vol pot to the max and measure frequency response again.
Turn on the vol pot to the max and measure frequency response again.
I am confused (nothing new I suppose).
I thought the OP was running the amp at high output levels and padding down the input to his analyzer via a resistive divider? I will have to find the post but I thought OP explicitly said he had the smiley face FR no matter where volume was😕
I thought the OP was running the amp at high output levels and padding down the input to his analyzer via a resistive divider? I will have to find the post but I thought OP explicitly said he had the smiley face FR no matter where volume was😕
I don't remember.
I don't like at all the loudness curve thing which supposedly makes music sound more enjoyable at low volume, this is utter BS.
We know how the loudness works with the input resistance of 100k so if it works like zenchenko said there is no purpose of checking it out.
If I listen to low volume the last thing I want to amplify is the very high and low frequencies, I want to hear the words of the singers which is in the 1khz region left out and covered with increased bass and high treble. BS , this is to sell amps making them sound greater than they are.
Normal listening level plays way too high with volume to 1/10 of the scale anyway on 91 db speakers.
I don't like at all the loudness curve thing which supposedly makes music sound more enjoyable at low volume, this is utter BS.
We know how the loudness works with the input resistance of 100k so if it works like zenchenko said there is no purpose of checking it out.
If I listen to low volume the last thing I want to amplify is the very high and low frequencies, I want to hear the words of the singers which is in the 1khz region left out and covered with increased bass and high treble. BS , this is to sell amps making them sound greater than they are.
Normal listening level plays way too high with volume to 1/10 of the scale anyway on 91 db speakers.
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