If it is Audible..i think the culprit is some sort of intermodulation ...which is similarly why bi, tri et al amp speaker setups tend to be superior...
In the first the main opamp is simply summing the output from each freq shaping network... It becomes additve or subtractuve based on the phasing..
In the second..the main opamp carries the entire burden of summing the shaping circuits whilst at the same time its global feed back network is being manipulated To produce the add/subtract feature...
In the first the main opamp is simply summing the output from each freq shaping network... It becomes additve or subtractuve based on the phasing..
In the second..the main opamp carries the entire burden of summing the shaping circuits whilst at the same time its global feed back network is being manipulated To produce the add/subtract feature...
Attachments
I don't think the use of a little EQ is a bad thing. The potential problem with it is the introduction of noise and HD caused by the method of filtering employed, especially when boosting certain frequency ranges rather than cutting them.
I'm actually a big proponent of EQ to replicate the intended so called psychoacoustic linearity which makes the frequency balance sound correct to the human ears at a given listening level, especially when it differs considerably from the original SPL the music was monitored at during the final mixdown process. Its In fact due to my pro audio background I discovered why some EQ may be needed to tame a bit of the midrange and treble peaking used during the mastering process.
Most conventionally produced pop / rock music isn't recorded with the goal of achieving the absolute realistic sound of specific instruments. There exists no exact reference of what a synthesizer or electric guitar is supposed to sound like in real life. These are manufactured, artifical sounds which are up to the individual subjective interpretation of the producer or engineer. This holds true for the individually miced elements of full drum kits. A good studio recording will employ the use of strategic EQ to allow for the acoustic "space" or separation needed to give each vocal or instrument better intelligibility in the whole mix (or mess for that matter). Sometimes dynamic processing is used to achieve the same thing ie. ducking and/or side chaining of drums, bass guitar and vocals, which gives certain instruments priority to be heard over others in certain situations.
All this and more is why contemporary multi track recordings aren't an exact science. Even the late great George Martin said a multi track pop / rock recording isn't supposed to be an exact xerox copy of something, but rather a hand painted portrait interpreted by a human artist.
These reasons are all valid arguments that support the use of a certain amount of EQ, as long as its not going to add considerable unpleasant (odd order) distortion. This is exactly why some older mixing consoles are so coveted by engineers, as they do such a great job of adding EQ and combining all the separate sound sources without imparting much of any objectionable character of their own. Rupert Neve designed some very good consoles in his day which are among the most sought after in the music production trade.
Analog tape machines also add some of that magic as well. I don't think anyone has ever objected to the sound a Studer 80 series tape machine can create. These machines sound amazing when used in the competent hands of an experienced engineer. This is thanks to the self imparted EQ and complicated dynamic compression analog tape adds to the original signal.
Classical and acoustic music can benefit from a more pure signal chain when they're recorded, but even those can benefit from some amount of EQ when recorded in good taste. I'm more of a purist than most engineers with the recording techniques I prefer to use. I don't see much harm in using higher end passive EQ as long as its done in a subtle and moderate way. I don't see this differing much from the mentality of using DSP to linearize a system in a given acoustical setting.
There are a few examples of very good EQ circuits. We wouldn't have decent sounding vinyl playback either without the needed RIAA eq. As long as you pay attention to noise and the required gain, EQ doesn't have to sound as bad as some people claim.
I'm actually a big proponent of EQ to replicate the intended so called psychoacoustic linearity which makes the frequency balance sound correct to the human ears at a given listening level, especially when it differs considerably from the original SPL the music was monitored at during the final mixdown process. Its In fact due to my pro audio background I discovered why some EQ may be needed to tame a bit of the midrange and treble peaking used during the mastering process.
Most conventionally produced pop / rock music isn't recorded with the goal of achieving the absolute realistic sound of specific instruments. There exists no exact reference of what a synthesizer or electric guitar is supposed to sound like in real life. These are manufactured, artifical sounds which are up to the individual subjective interpretation of the producer or engineer. This holds true for the individually miced elements of full drum kits. A good studio recording will employ the use of strategic EQ to allow for the acoustic "space" or separation needed to give each vocal or instrument better intelligibility in the whole mix (or mess for that matter). Sometimes dynamic processing is used to achieve the same thing ie. ducking and/or side chaining of drums, bass guitar and vocals, which gives certain instruments priority to be heard over others in certain situations.
All this and more is why contemporary multi track recordings aren't an exact science. Even the late great George Martin said a multi track pop / rock recording isn't supposed to be an exact xerox copy of something, but rather a hand painted portrait interpreted by a human artist.
These reasons are all valid arguments that support the use of a certain amount of EQ, as long as its not going to add considerable unpleasant (odd order) distortion. This is exactly why some older mixing consoles are so coveted by engineers, as they do such a great job of adding EQ and combining all the separate sound sources without imparting much of any objectionable character of their own. Rupert Neve designed some very good consoles in his day which are among the most sought after in the music production trade.
Analog tape machines also add some of that magic as well. I don't think anyone has ever objected to the sound a Studer 80 series tape machine can create. These machines sound amazing when used in the competent hands of an experienced engineer. This is thanks to the self imparted EQ and complicated dynamic compression analog tape adds to the original signal.
Classical and acoustic music can benefit from a more pure signal chain when they're recorded, but even those can benefit from some amount of EQ when recorded in good taste. I'm more of a purist than most engineers with the recording techniques I prefer to use. I don't see much harm in using higher end passive EQ as long as its done in a subtle and moderate way. I don't see this differing much from the mentality of using DSP to linearize a system in a given acoustical setting.
There are a few examples of very good EQ circuits. We wouldn't have decent sounding vinyl playback either without the needed RIAA eq. As long as you pay attention to noise and the required gain, EQ doesn't have to sound as bad as some people claim.
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What about phase "distortion"? Imagine the usual "palette" of boost / cut bands, that when all mixed together give a flat response. Someone picks out a center frequency for each and assembles a sequence of repeating circuits to cover the audible bandwidth.
So let's say a sound comes in, hits one of the center frequencies dead on. No phase shift, as the circuit theory tells us. But let's say the sound lands just south of the center frequency. Now the curve of the bandpass looks like a HP filter and with that curve, a corresponding phase lead. Let's say the sound lands just north of the center frequency. Now the curve of the bandpass looks like a LP filter and with that curve, phase lag.
Since music - sound - can be anywhere relative to the band center frequencies, now one can imagine this lead-lag-lead-lag-lead-lag thing going on across the range of the band adjustable EQ device. Is this what you "give up in order to have" the ability to arbitrarily equalize signal amplitude?
I will deal with the negativess first...
If you do NOT have the identical speakers and almost the identical environment that the engieneers did their mixing/ equing then you will hear a pseudo copy of the actual sound in the studio....
The WHOLE concept for eq to me is to make things PLEASANT TO THE EAR...not to reach some ideal in the darkness... If the eq does not mux up any other part of the bandwidth who in their right mind would refuse to use one that absolutely adds punch power and depth to their bass? This is the essence of why we eq...not in pursuit of some absolute..but to make the music bring tears to your eyes ... That's ALL of it.
Please refer to my little history i gave about my demo that got 5 stars... It was how the music IMPACTED them that counted... The boss already heard that song a hundred times a day..yet he teared up.... I simply compensated for the way the speakera sounded to MY EARS in THAT room and i think i made the right choices...my VERY hard to please boss was well...pleased.. THIS IS WHAT MATTERS...NOT SOME ABSOLUTE untouchable aim
The mona lisa is NOT a perfect picture.. how could it be? it's not an exact replicate of a REAL living human being... so ART is just that..an expression that others can appreciate..this does not lower its value just because it is not REAL... Sculpting painting music are all art forms to bring joy to life -they are not necessities like food which MUST have minerals vitamins proteins fats etc... yet their is ART in food preparation...for you can have food without taste.. unpalatable...
So the conclusion... Gentlemen and ladies, we are trying to find a PLEASANT sounding playback eq that can mitigate swapping cables, tame the top end of a beryllium tweeter without getting rid if its "air"...
Lets find that master piece and we can ALL agree and appreciate alike a $20k sundae or a priceless mona lisa....
If you do NOT have the identical speakers and almost the identical environment that the engieneers did their mixing/ equing then you will hear a pseudo copy of the actual sound in the studio....
The WHOLE concept for eq to me is to make things PLEASANT TO THE EAR...not to reach some ideal in the darkness... If the eq does not mux up any other part of the bandwidth who in their right mind would refuse to use one that absolutely adds punch power and depth to their bass? This is the essence of why we eq...not in pursuit of some absolute..but to make the music bring tears to your eyes ... That's ALL of it.
Please refer to my little history i gave about my demo that got 5 stars... It was how the music IMPACTED them that counted... The boss already heard that song a hundred times a day..yet he teared up.... I simply compensated for the way the speakera sounded to MY EARS in THAT room and i think i made the right choices...my VERY hard to please boss was well...pleased.. THIS IS WHAT MATTERS...NOT SOME ABSOLUTE untouchable aim
The mona lisa is NOT a perfect picture.. how could it be? it's not an exact replicate of a REAL living human being... so ART is just that..an expression that others can appreciate..this does not lower its value just because it is not REAL... Sculpting painting music are all art forms to bring joy to life -they are not necessities like food which MUST have minerals vitamins proteins fats etc... yet their is ART in food preparation...for you can have food without taste.. unpalatable...
So the conclusion... Gentlemen and ladies, we are trying to find a PLEASANT sounding playback eq that can mitigate swapping cables, tame the top end of a beryllium tweeter without getting rid if its "air"...
Lets find that master piece and we can ALL agree and appreciate alike a $20k sundae or a priceless mona lisa....
I can assure you that adding a little corrective EQ to a recording isn't going to significantly change its overall character any more than your playback chain itself will impart to the recording you're listening to. I really dont consider any contemporary music recording to be comparable to the Mona Lisa in terms of being pristine or pure. If you knew how much butchery takes place in the studio (harmonizers, compressors, gates, reverb, etc adding fluff nd sparkle) you'd be shocked it can still sound as good as it is perceived when played back through even a high end system. Everything adds something which isn't there to begin with. A few dB here and there isn't going to ruin anything. On the contrary, it can really help. The main thing to keep in mind is its all subjective.
Sure, phase distortion can be an issue if its out of wack by alot. How much of it can you perceive? Thats debatable due to no specific standard reference of audibility threshold. I can guarantee though, once it all goes through a typical multi-way speaker and gets contorted, its all game over. The crossover will create multiple sonic events of its own, at least one for each driver if it employs 2nd or higher order filters. As long as the 300 hz - 10k range is void of significant phase shifts, you'll have subjectively good imaging and detail but there is also the issue of early reflections and baffle induced diffraction. Group delay is another big one. The list goes on...
Temporal distortion is another big different issue which adds to the can of worms we have to deal with trying to reproduce life like audio. You have to pick your poison and prioritize what's more important to you. I have no issues with using a little EQ if I feel it sounds appropriate to my ears. Usually I prefer no EQ whatsoever, but its rare to have well balanced vocals which don't have some peaking response. Just about every decent vocal mic imparts its own character to the recording and that amount can be extreme if you heard how much of a difference there was compared to a ruler flat sounding mic. Most engineers won't use a flat sounding mic because it won't flatter the vocals.
There is an excellent test track on one of Stereophile's test CDs narrated by the late J. G. Holt which shows the individual sonic traits of many commonly used and coveted studio mics. Its amazing how different they all sound, yet most of these mics are considered to be standards by many engineers. Despite the different FR of each mic, they can produce excellent sounding recordings. Maybe I can post the .wav file of this track if the mods were ok with it. Its a real eye opener as to how different these mics all sound with the same source.
Sure, phase distortion can be an issue if its out of wack by alot. How much of it can you perceive? Thats debatable due to no specific standard reference of audibility threshold. I can guarantee though, once it all goes through a typical multi-way speaker and gets contorted, its all game over. The crossover will create multiple sonic events of its own, at least one for each driver if it employs 2nd or higher order filters. As long as the 300 hz - 10k range is void of significant phase shifts, you'll have subjectively good imaging and detail but there is also the issue of early reflections and baffle induced diffraction. Group delay is another big one. The list goes on...
Temporal distortion is another big different issue which adds to the can of worms we have to deal with trying to reproduce life like audio. You have to pick your poison and prioritize what's more important to you. I have no issues with using a little EQ if I feel it sounds appropriate to my ears. Usually I prefer no EQ whatsoever, but its rare to have well balanced vocals which don't have some peaking response. Just about every decent vocal mic imparts its own character to the recording and that amount can be extreme if you heard how much of a difference there was compared to a ruler flat sounding mic. Most engineers won't use a flat sounding mic because it won't flatter the vocals.
There is an excellent test track on one of Stereophile's test CDs narrated by the late J. G. Holt which shows the individual sonic traits of many commonly used and coveted studio mics. Its amazing how different they all sound, yet most of these mics are considered to be standards by many engineers. Despite the different FR of each mic, they can produce excellent sounding recordings. Maybe I can post the .wav file of this track if the mods were ok with it. Its a real eye opener as to how different these mics all sound with the same source.
Profiguy....
My hats off to you sir .... You said ALL of everything ever necessary to say about the purpose of eq or any signal processing... they need you to do lectures in university...
There is nothing that you said that i disagree with...i guess your pro experience have taught you to avoid the ideological nonsense that pervades the industry... Chose of eq or processing is ART in the studio...no different from choice of paint and textures... Our job is to hear/see our Art as clearly as possible... No one , in their right mind,is gonna take a mona lisa and hang it in an extremely dim lit room behind a door... you are going to highlight its majesty by lighting and placement...
Why do we argue that we ahould do the same for our music..? its nonsensical...
Let us find the BEST light for our music after we have done all the best placement -speaker positioning etc, possible THEN use the best EQ we xan afford to do the job of making us fall in love with the ART of audio day in day out...
My compliments to ALL of you contributers...
My hats off to you sir .... You said ALL of everything ever necessary to say about the purpose of eq or any signal processing... they need you to do lectures in university...
There is nothing that you said that i disagree with...i guess your pro experience have taught you to avoid the ideological nonsense that pervades the industry... Chose of eq or processing is ART in the studio...no different from choice of paint and textures... Our job is to hear/see our Art as clearly as possible... No one , in their right mind,is gonna take a mona lisa and hang it in an extremely dim lit room behind a door... you are going to highlight its majesty by lighting and placement...
Why do we argue that we ahould do the same for our music..? its nonsensical...
Let us find the BEST light for our music after we have done all the best placement -speaker positioning etc, possible THEN use the best EQ we xan afford to do the job of making us fall in love with the ART of audio day in day out...
My compliments to ALL of you contributers...
@genrose I do agree with the bottom line of what you're saying. Adding a little EQ won't destroy anything. If its about making the music pleasing to the individual ear, then its all good. Everyone has different ears and its up to you what you prefer. Even though I'm a purist when it comes to playback, I don't see why a little EQ can hurt as much as some people say it will. Your speakers will impart their own EQ among the other many things they add as well, which can and will be much worse on their own.
Profiguy....
Now you seem to be back tracking a lil bit.. but thars ok...
I am not a recording engineer..im am the guy they call when things dont work... And or they need systems out together..
I ABSOLUTELY know what you mean by mics with their idiosyncratic sound and all that.. but again that is neither here or there...why are we worried about HOW the chef cooked the food ...? Why should i worry how sting recorded "fragile"... All i know is when people who NEVER Listen to that sort of music hear this sing over a properly set up sytem thay are reduced to staying still, shutting up... Fighting back tears...in that order...
That is all that matters...
And again...not EVERY playback system will do this...why? Because they DO contribute a CHARACTER to the prerecorded sound...
I like women .they are blatantly honest... Especially about things they wouldn't really take a second glance at so their words mean a lot to me when it comes to playback systems.... Well i have women who told me days afterwards that i have SPOILED ALL PLAYBACK SYSTEMS That they have ever heard in their life And cringe now when trying to listen to their fav song again via their old media playback methods .. its takes weeks to desyntheise oneself after such an experience...
I had a long term girlfriend who was a recording artist... Do you know how she judged if she really likes the sound of her finished songs? When she takes them home and listens on OUR system... Who am i to argue? I am NOT the artist..
That system influenced her taste and broadened her appreciation in music ... The playback system made her a BETTER artis..just like any prospective artist gets inspiration from a Mona Lisa ..
Your playback character matters...
Now you seem to be back tracking a lil bit.. but thars ok...
I am not a recording engineer..im am the guy they call when things dont work... And or they need systems out together..
I ABSOLUTELY know what you mean by mics with their idiosyncratic sound and all that.. but again that is neither here or there...why are we worried about HOW the chef cooked the food ...? Why should i worry how sting recorded "fragile"... All i know is when people who NEVER Listen to that sort of music hear this sing over a properly set up sytem thay are reduced to staying still, shutting up... Fighting back tears...in that order...
That is all that matters...
And again...not EVERY playback system will do this...why? Because they DO contribute a CHARACTER to the prerecorded sound...
I like women .they are blatantly honest... Especially about things they wouldn't really take a second glance at so their words mean a lot to me when it comes to playback systems.... Well i have women who told me days afterwards that i have SPOILED ALL PLAYBACK SYSTEMS That they have ever heard in their life And cringe now when trying to listen to their fav song again via their old media playback methods .. its takes weeks to desyntheise oneself after such an experience...
I had a long term girlfriend who was a recording artist... Do you know how she judged if she really likes the sound of her finished songs? When she takes them home and listens on OUR system... Who am i to argue? I am NOT the artist..
That system influenced her taste and broadened her appreciation in music ... The playback system made her a BETTER artis..just like any prospective artist gets inspiration from a Mona Lisa ..
Your playback character matters...
profiguy..
We both agree in the big stuff sir ..
Thumbs up
Now lets get to that elusive nice sounding eq .....
Wow ..ok..i just remembered another lil bit of history... I stole the design of a mutitrack mixer by literallly back engineering the design from its circuit borad...why ..? Beacaue it sounded so freaking good.. and i implemented it into a preamp i had desiged .. it was the best preamp around, EVERYONE who ever heard is said that...i agred.. please remember i wasn't the designer...i just picked the right sounding one...
I could actually go back to that design but i heard its short comings one day when i tried to chain in betwen some VERY HIGH end equipment..it stood out like a sore thumb... not too terrible but
.not transparent enough...
Hence my quest, AGAIN
We both agree in the big stuff sir ..
Thumbs up
Now lets get to that elusive nice sounding eq .....
Wow ..ok..i just remembered another lil bit of history... I stole the design of a mutitrack mixer by literallly back engineering the design from its circuit borad...why ..? Beacaue it sounded so freaking good.. and i implemented it into a preamp i had desiged .. it was the best preamp around, EVERYONE who ever heard is said that...i agred.. please remember i wasn't the designer...i just picked the right sounding one...
I could actually go back to that design but i heard its short comings one day when i tried to chain in betwen some VERY HIGH end equipment..it stood out like a sore thumb... not too terrible but
.not transparent enough...
Hence my quest, AGAIN
I've searched a long time for that so called transparent EQ that isn't supposed to exist. I feel the best solution to the problem is using passive networks with very high quality stepped attenuators and the best, reasonably priced capacitors available. I believe real inductors sound better than simulating them actively with gyrator circuits, which add noise. Winding your own inductors is IMO the best solution unless you have access to decent inductors. Winding them yourself allows you to create stepped values which save money and produce better inductors not having to connect them in series. I like the sound of the old Ampeg EQ circuir used in the older portaflex bass amps. Those use inductors as well.
For buffering the output, using a decent NE5532/LM4562 bipolar op amp can have the best potential performance without resorting to scarcely available boutique parts. You could also transformer couple them with Jensen or Lundahl units.
I've literally tried every common available parametric EQ on the market. Most are too noisy and sound too veiled. I did use a Massenburg GML8200 and loved it. That was a $8k unit and placed on the monitor bus going to my old PMCs, mainly used for mastering. They didn't need much of any EQ, but the material I then worked on was solo piano music, likely the hardest instrument on earth to reproduce.
Baxandall EQs are another option but their interactive properties make them difficult to practically implement for predictable results.
For buffering the output, using a decent NE5532/LM4562 bipolar op amp can have the best potential performance without resorting to scarcely available boutique parts. You could also transformer couple them with Jensen or Lundahl units.
I've literally tried every common available parametric EQ on the market. Most are too noisy and sound too veiled. I did use a Massenburg GML8200 and loved it. That was a $8k unit and placed on the monitor bus going to my old PMCs, mainly used for mastering. They didn't need much of any EQ, but the material I then worked on was solo piano music, likely the hardest instrument on earth to reproduce.
Baxandall EQs are another option but their interactive properties make them difficult to practically implement for predictable results.
Thanks for the reference to the Massenburg...
I agree with you .. transparency is the greatest and most elusive attribute of a good eq... your circuit design suggestions are well taken. but not only that, the DESIGN as i implicated earlier is also to blame... I think it is having the caps and gyrators or even real inductors - resonant circuits- within the feedback nest loop of the circuit that causes issues..
Someone suggested earlier about checking wein bride oscillators and there is our clue .. oscillators "ring"... And the typical eq design is pretty close to a wein bridge...I believe the layout i provided and 3 orher high end brands agree is the way to go...
i think the sound shaper series of eqs in the early nineties epitomised what was possible with real inductors /caps etc but the same typical circuit design was used... I am staying away from that design concept entirely...
I believe there is an optinmal circuit design and with proper gyrators we can get very close to the transparency we seek...i really wish we could get someone on here who has experience with the FM acoustics or that sony unit...
5 overlapping bands i think is the optimal number... I was checking some live sound mixer YouTuber channles and there is a correlation of eq settings that seems to be pleasing to the ears...i am centerinng my 5 bands around those central frequenies...Fm Acoustics probably did all that leg work for me because it is very close to those guys also ..
i dont want anyone to get the idea that we need tons of gain or reduction..a few dBs in either direction will produce the required slope that heightens or tames the " i wish it had a little more of this or less of that" factor...
Thanks for all the contributions so far..
I agree with you .. transparency is the greatest and most elusive attribute of a good eq... your circuit design suggestions are well taken. but not only that, the DESIGN as i implicated earlier is also to blame... I think it is having the caps and gyrators or even real inductors - resonant circuits- within the feedback nest loop of the circuit that causes issues..
Someone suggested earlier about checking wein bride oscillators and there is our clue .. oscillators "ring"... And the typical eq design is pretty close to a wein bridge...I believe the layout i provided and 3 orher high end brands agree is the way to go...
i think the sound shaper series of eqs in the early nineties epitomised what was possible with real inductors /caps etc but the same typical circuit design was used... I am staying away from that design concept entirely...
I believe there is an optinmal circuit design and with proper gyrators we can get very close to the transparency we seek...i really wish we could get someone on here who has experience with the FM acoustics or that sony unit...
5 overlapping bands i think is the optimal number... I was checking some live sound mixer YouTuber channles and there is a correlation of eq settings that seems to be pleasing to the ears...i am centerinng my 5 bands around those central frequenies...Fm Acoustics probably did all that leg work for me because it is very close to those guys also ..
i dont want anyone to get the idea that we need tons of gain or reduction..a few dBs in either direction will produce the required slope that heightens or tames the " i wish it had a little more of this or less of that" factor...
Thanks for all the contributions so far..
You'll should read this article...
The Massenberg
https://www.attackmagazine.com/technique/hardware-focus/gml-8200-eq/
Subjectivity aside ...
We all hear the same way using the same nodes....frequency phase/timing and pressure (loudness)....
Every difference we perceive between amp or preamp we have ever heard is through these phenomena...hence my slight obsession with eq... basically im saying it MUST BE in these phenomena that we find rhe reason why one amp sounds wide another deep and narrow, more punchy etc ..i am speaking STRICTLY from the perpective of listening not what parameters are at present in an amp at any given moment, freq dependent damping factor, etc..... I wish there was a spec sheet somewhere a white oaoer perhaps that layouts through research which of these 3 agents describe the phenomena we hear when we hear differences between equipment....
Im ABSOLUTELY SURE THE MILITARY KNOWS...imaging the 360 degree soundfield in the helmet of a F35...
I once saw a video with a blindfolded student pointing correctly to the source of sound played back through headset.. laterally and vertically...
they were developing some sort of aural processing
The Massenberg
https://www.attackmagazine.com/technique/hardware-focus/gml-8200-eq/
Subjectivity aside ...
We all hear the same way using the same nodes....frequency phase/timing and pressure (loudness)....
Every difference we perceive between amp or preamp we have ever heard is through these phenomena...hence my slight obsession with eq... basically im saying it MUST BE in these phenomena that we find rhe reason why one amp sounds wide another deep and narrow, more punchy etc ..i am speaking STRICTLY from the perpective of listening not what parameters are at present in an amp at any given moment, freq dependent damping factor, etc..... I wish there was a spec sheet somewhere a white oaoer perhaps that layouts through research which of these 3 agents describe the phenomena we hear when we hear differences between equipment....
Im ABSOLUTELY SURE THE MILITARY KNOWS...imaging the 360 degree soundfield in the helmet of a F35...
I once saw a video with a blindfolded student pointing correctly to the source of sound played back through headset.. laterally and vertically...
they were developing some sort of aural processing
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Well it is possible to locate sound origin im the horizontal plane if there is a time specific event connected to it. Steady state sounds don't locate well unless they occur in anechoic environment and are above the wavelength representative of the distance between our ears. The brain is very good at temporal distinguished sounds, even complex ones.
Gyrator circuits are flawed by their reactive nature of distortion components which cause odd order harmonics to be generated, which vary depending on several design aspects. I have several klark DN410s in my subwoofer setup, which do well in that designated band, but sound very stale and congested in the midrange on up, despite being heavily modified with Lundahl xformers and class A buffer stages.
I agree using the feedback loop to process audio is never a good idea. It never seems to work well. I've tried everything from phono stages to crossovers using op amp FB loops with poor results. Passive networks between non-inverting stages work best. That rules out filters higher than 2nd order unless they're staggered. I believe its the result of bon linear impedance loading of filters which cause most of the problems. The lower the load impedance is pushed by passive resistance, the cleaner the results. Same holds true for any type of bandpass circuit. At higher impedances the linearity errors add up fast. Things like potentiometers, capacitors and other passive parts produce higher odd order harmonics, especially at higher voltages along with higher impedance sources and lighter loads.
Your wien bridge theory isn't that far off. That problem exists for just about any higher Q filter with minimal dampening. Really any filter 2nd order or higher can be made to oscillate under the right conditions. Negative feedback loops can be very fragile in terms of noise and non linearity ingress.
Filter Q of .707 and higher are underdampened, even when combined with lower Q stages. Local feedback must be kept in check at any point. Thats one reason why some amplifiers sound better than others. It has alot to do with absolute stability and every single gain or drive stage needs to have sufficient local feedback across a wide FR to retain its control.
Using global feedback to fix the problem never works, as it only magnifies any single stage deficiencies in the chain. High open loop gain is a good thing, but only if it doesn't come with any inherent instability at the upper range and only when it's driven in its linear range. Thats why these big mish mash designs with a billion op amps never sound good at higher frequencies. There are too many places where linearity is achieved through high levels of feedback to mask lower open loop gain linearity. The overall mis behavior of each op amp stage is magnified at every step of the way.
Gyrator circuits are flawed by their reactive nature of distortion components which cause odd order harmonics to be generated, which vary depending on several design aspects. I have several klark DN410s in my subwoofer setup, which do well in that designated band, but sound very stale and congested in the midrange on up, despite being heavily modified with Lundahl xformers and class A buffer stages.
I agree using the feedback loop to process audio is never a good idea. It never seems to work well. I've tried everything from phono stages to crossovers using op amp FB loops with poor results. Passive networks between non-inverting stages work best. That rules out filters higher than 2nd order unless they're staggered. I believe its the result of bon linear impedance loading of filters which cause most of the problems. The lower the load impedance is pushed by passive resistance, the cleaner the results. Same holds true for any type of bandpass circuit. At higher impedances the linearity errors add up fast. Things like potentiometers, capacitors and other passive parts produce higher odd order harmonics, especially at higher voltages along with higher impedance sources and lighter loads.
Your wien bridge theory isn't that far off. That problem exists for just about any higher Q filter with minimal dampening. Really any filter 2nd order or higher can be made to oscillate under the right conditions. Negative feedback loops can be very fragile in terms of noise and non linearity ingress.
Filter Q of .707 and higher are underdampened, even when combined with lower Q stages. Local feedback must be kept in check at any point. Thats one reason why some amplifiers sound better than others. It has alot to do with absolute stability and every single gain or drive stage needs to have sufficient local feedback across a wide FR to retain its control.
Using global feedback to fix the problem never works, as it only magnifies any single stage deficiencies in the chain. High open loop gain is a good thing, but only if it doesn't come with any inherent instability at the upper range and only when it's driven in its linear range. Thats why these big mish mash designs with a billion op amps never sound good at higher frequencies. There are too many places where linearity is achieved through high levels of feedback to mask lower open loop gain linearity. The overall mis behavior of each op amp stage is magnified at every step of the way.
This, I did not know. Add it to the other things I've learned here recently -
- An amp with a little bit of feedback is the worst thing you can do.
- An amp with gain can be more transparent than a resistor divider attenuation.
Sir...i dont know who you are but SPOT on you are indeed... Im encouraged that others KNOW EXACTLY what im talking about.... I don't wanna be feeling like that ufo guy...(they do exist but that's another story for elsewhere) ..
Im gonna let out a secret, -something the industry refuses to measure, specify and develop a load test for in order to single out the great designs from the rest - i KNOW it is the damping factor AND its constancy of linearity under DYNAMIC load which determines how amplifiers sound... It's not necessarily just how high the damping factor is - how low the impedance is. It is its STABILITY..
Carver used resistors in series with his amp outputs to simulate the higher output Z of a tube amp... Speaker drivers generally sound better driven through a resistor - i known this like 40 years.. your tweeters are also nicer when series resistors are added..
NON LINEAR impedances -otherwise called damping factor - is the key.. this is why amplifiers like The Burmester 150 mono exist... You can tailor the amp to the speaker in question...
In my case.. the perfect eq will be just as you described...2nd order networks between quality impedance dampening preamp circuits ....That is my design approach...
Thanks for all the inputs..
Profiguy, your insights are golden - and speak volumes in experience
That's it right there.... that's my thought exactly... Ive seen that two stage RIAA contour in some top tier phono preamp for the same reason as you asserted...
Im gonna let out a secret, -something the industry refuses to measure, specify and develop a load test for in order to single out the great designs from the rest - i KNOW it is the damping factor AND its constancy of linearity under DYNAMIC load which determines how amplifiers sound... It's not necessarily just how high the damping factor is - how low the impedance is. It is its STABILITY..
Carver used resistors in series with his amp outputs to simulate the higher output Z of a tube amp... Speaker drivers generally sound better driven through a resistor - i known this like 40 years.. your tweeters are also nicer when series resistors are added..
NON LINEAR impedances -otherwise called damping factor - is the key.. this is why amplifiers like The Burmester 150 mono exist... You can tailor the amp to the speaker in question...
In my case.. the perfect eq will be just as you described...2nd order networks between quality impedance dampening preamp circuits ....That is my design approach...
Thanks for all the inputs..
Profiguy, your insights are golden - and speak volumes in experience
False dilemma there - clearly you make a good amp and add a lot of feedback for the best results, standard practice in fact... Its typically the output stage that is the hardest to linearize, and a little feedback is probably worse than useless for that. Best output stage linearity uses local feedback in the O.S. itself and then much global feedback around it as well. Well that's how to get to <10ppm THD at 1kHz with realistic budget...