Amplifier Feedback Good or Bad?

Is Too Much Negative Feedback in Audio Amplifiers Bad?

  • Yes. The best sounding amps use less or no feedback.

    Votes: 4 21.1%
  • No. The best sounding and performaning amps use lots of feedback.

    Votes: 9 47.4%
  • What's feedback feedback feedback feedback....?

    Votes: 6 31.6%

  • Total voters
    19
highfigh

highfigh

Audioholic Overlord
I can't even hear beyond 16kHz, but you can hear to 200kHz?

And you would buy an amp with a SNR of 90dBA even if you could buy an amp with a SNR of 132dBA?
An amp that can reproduce 200K will be very unlikely to produce distortion in the audible range and an octave above. The higher order THD components are objectionable and wide bandwidth amps tend to produce less of this distortion.

I have no problem with -90dB SN. It's not the reason I buy an amp, but it would be a likely reason for choosing a source. I don't listen at high enough SPL that my equipment's noise is audible when the music stops.
 
highfigh

highfigh

Audioholic Overlord
Psychoacoustics, in my opinion, relevant whenever the question of whether something is good or bad is when it comes to designing a piece of audio gear such as amps. So is Amplifier Feedback Good or Bad? If it adversely affect sound quality, then yes it is bad. BTW, the psychoacoustic deals objective results as well, it's about what the human ear can hear.
Psychoacoustics is not objective, it involves the way we perceive certain sounds rather than how our auditory system actually receives them, e.g., 4KHz tones sound like they're coming from the side, 8KHz sounds like its coming from directly overhead, regardless of which ear is receiving the input. It has nothing to do with flat frequency response acuity (or closely following the Fletcher-Munson, et al curves) or anything like that- the fact that 'psycho' is part of the word should make it obvious that the mind is involved.
 
highfigh

highfigh

Audioholic Overlord
Well, that's just too bad, Mike!

If you had bigger ears, you could be enjoying amps with No Negative Feedback that have Frequency Response of 0.0Hz-200kHz +/- 0.1dB. :D
Hey, hey, hey! I never wrote anything about amplifiers that can do DC and I totally resent you referring to something I posted without mentioning me. do that again and we'll have words, buster!o_O
 
highfigh

highfigh

Audioholic Overlord
  • Over the last 10 years, the sonic differences between acceptable audio and superb audio has widen significantly
Is this due to the acceptable level dropping, or because the superb audio quality improving, and to what degree?
 
Gmoney

Gmoney

Audioholic General
Psychoacoustics is not objective, it involves the way we perceive certain sounds rather than how our auditory system actually receives them, e.g., 4KHz tones sound like they're coming from the side, 8KHz sounds like its coming from directly overhead, regardless of which ear is receiving the input. It has nothing to do with flat frequency response acuity (or closely following the Fletcher-Munson, et al curves) or anything like that- the fact that 'psycho' is part of the word should make it obvious that the mind is involved.
Nice post, makes sense to me sound after all is Reflective. As for Psychoacoustic”s” now thats a Very subjective subject to discuss which could be and has been applied to audio. One group says I heard that the other group says You heard that. No Presumption shouldn’t be Included with any True audio testing. Why rely on the word of the Listener when it really can not be Proven. Double blind test as fun as they are with a bunch of Audiophools with so called trained golden ears are the last one’s I’d take Advice from. But than it would be Interesting to say the least to standby a couple of them listen to the discussion between the two or three see who’ll jumps out of that Circle jerk first. ;):)
 
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M Code

M Code

Audioholic General
Is this due to the acceptable level dropping, or because the superb audio quality improving, and to what degree?
A couple of reasons.. :)
Wider distribution for lower bit-rate compressed streams, and playback back through lower quality audio systems such as cell phones, tablets, sound-bars, desktop multi-media speakers. On the higher side, more powerful processors with increased resources,, advanced digital protocols not only for audio/video and just audio..

Regarding degree, harder to quantify but now we have MP3 compressed streams, for example XM/Sirius satellite radio broadcasts in 64K, while multiple lossless, uncompressed formats are widely available. The point I am trying to make is... Todays' audio content is available in a wide-variety with many different formats, and its delivered sonic quality can/will vary greatly depending upon the carrier and playback device..

Just my $0.02... ;)
 
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highfigh

highfigh

Audioholic Overlord
Nice post, makes sense to me sound after all is Reflective. As for Psychoacoustic”s” now thats a Very subjective subject to discuss which could be and had been applied to audio. One group says I heard that the other group says You heard that. No Presumption shouldn’t be Included with any True audio testing. Why rely on the word of the Listener when it really can not be Proven. Double blind test as fun as they are with a bunch of Audiophools with so called trained golden ears are the last one’s I’d take Advice from. But than it would be Interesting to say the least to standby a couple of them listen to the discussion between the two or three see who’ll jumps out of that Circle jerk first. ;):)

The sound doesn't need to come from speakers, it can come from headphones, too. The book 'Master Handbook of Acoustics' has a section for Psychoacoustics and it has a lot of info that's useful. For that matter, it has a lot of good info for anyone who's interested in acoustics.

I went for a hearing test not long after reading this book and when I heard some frequencies, specifically 4K ad 8K, I asked her to re-test them and I listened for the perceived location of the sound and when I knew what to listen for, I was able to hear it at a lower level. One person't hearing acuity will allow them to hear the spread of the soundstage differently from someone who has a deficit in the range where separation is in the 4K range and in the studio, emphasis/de-emphasis on certain frequencies makes it possible to make the soundstage wider, higher and with phase controls, deeper.

It's not about a peeing contest, golden ears or anything like those, it's a matter of the sound's energy that is physically sensed by the ears (auditory nerve stimulation) and how the brain processes it. Knowledge of this is actually helpful in listening and when someone knows what to listen for, it's possible to hear sounds differently from the way someone else hears them. Again, it's not a competition, it's training to hear differences. If someone has used equalizers and adjusted them in small increments, they'll learn the difference in smaller increments. Someone who has only listened to large increments will probably miss the small ones until they reach a larger difference. If you have the chance to make settings in a Denon AVR with speaker distance settings, play with them in the .1 foot and 1 foot increments. It's definitely audible. Do this at low and moderate levels and listen for the differences- at high SPL, it will be more difficult in a reverberent room.
 
highfigh

highfigh

Audioholic Overlord
A couple of reasons.. :)
Wider distribution for lower bit-rate compressed streams, and playback back through lower quality audio systems such as cell phones, tablets, sound-bars, desktop multi-media speakers. On the higher side, more powerful processors with increased resources,, advanced digital protocols not only for audio/video and just audio..

Regarding degree, harder to quantify but now we have MP3 compressed streams, for example XM/Sirius satellite radio broadcasts in 64K, while multiple lossless, uncompressed formats are widely available. The point I am trying to make is... Todays' audio content is available in a wide-variety with many different formats, and its delivered sonic quality can/will vary greatly depending upon the carrier and playback device..

Just my $0.02... ;)
If you have been an XM user, was this during the time when they merged with Sirius? The Sirius channels I heard sounded like crap, IMO. The XM were OK, but I didn't really expect great sound- I used it for the content. The bad sound and their dropping of the main channels I listened to made it easy to drop them. Well, those and the price hike.
 
Gmoney

Gmoney

Audioholic General

The sound doesn't need to come from speakers, it can come from headphones, too. The book 'Master Handbook of Acoustics' has a section for Psychoacoustics and it has a lot of info that's useful. For that matter, it has a lot of good info for anyone who's interested in acoustics.

I went for a hearing test not long after reading this book and when I heard some frequencies, specifically 4K ad 8K, I asked her to re-test them and I listened for the perceived location of the sound and when I knew what to listen for, I was able to hear it at a lower level. One person't hearing acuity will allow them to hear the spread of the soundstage differently from someone who has a deficit in the range where separation is in the 4K range and in the studio, emphasis/de-emphasis on certain frequencies makes it possible to make the soundstage wider, higher and with phase controls, deeper.

It's not about a peeing contest, golden ears or anything like those, it's a matter of the sound's energy that is physically sensed by the ears (auditory nerve stimulation) and how the brain processes it. Knowledge of this is actually helpful in listening and when someone knows what to listen for, it's possible to hear sounds differently from the way someone else hears them. Again, it's not a competition, it's training to hear differences. If someone has used equalizers and adjusted them in small increments, they'll learn the difference in smaller increments. Someone who has only listened to large increments will probably miss the small ones until they reach a larger difference. If you have the chance to make settings in a Denon AVR with speaker distance settings, play with them in the .1 foot and 1 foot increments. It's definitely audible. Do this at low and moderate levels and listen for the differences- at high SPL, it will be more difficult in a reverberent room.
Sure A “trained” ear of a 65 year old person may or may Not be able to hear what a 25 year old can or cannot hear. Also never in my post did I say Speakers only when “Psycho” the “Mind” is being Applied. Sure headphones why not? Psychoacoustics has been used and it has with audio from the very start. When used with Designing an amplifier, case in point Bob Caver, with his Signature amp Designs where loved by many myself Including. His TFM-amps has His Psycho-Acoustics built in. But the thing about that Design your stuck with it. Bobs amps those TFM amps at least where Never associated with as being neutral. So Psychoacoustics very Broad and subjective. Don’t take one of my Sentences out of Context. Sure it isn’t about a pissing Contest don’t Insult my intelligence my post was ment to cover how Broadly the use of Psychoacoustics in audio.
 
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Pogre

Pogre

Audioholic Warlord

The sound doesn't need to come from speakers, it can come from headphones, too. The book 'Master Handbook of Acoustics' has a section for Psychoacoustics and it has a lot of info that's useful. For that matter, it has a lot of good info for anyone who's interested in acoustics.

I went for a hearing test not long after reading this book and when I heard some frequencies, specifically 4K ad 8K, I asked her to re-test them and I listened for the perceived location of the sound and when I knew what to listen for, I was able to hear it at a lower level. One person't hearing acuity will allow them to hear the spread of the soundstage differently from someone who has a deficit in the range where separation is in the 4K range and in the studio, emphasis/de-emphasis on certain frequencies makes it possible to make the soundstage wider, higher and with phase controls, deeper.

It's not about a peeing contest, golden ears or anything like those, it's a matter of the sound's energy that is physically sensed by the ears (auditory nerve stimulation) and how the brain processes it. Knowledge of this is actually helpful in listening and when someone knows what to listen for, it's possible to hear sounds differently from the way someone else hears them. Again, it's not a competition, it's training to hear differences. If someone has used equalizers and adjusted them in small increments, they'll learn the difference in smaller increments. Someone who has only listened to large increments will probably miss the small ones until they reach a larger difference. If you have the chance to make settings in a Denon AVR with speaker distance settings, play with them in the .1 foot and 1 foot increments. It's definitely audible. Do this at low and moderate levels and listen for the differences- at high SPL, it will be more difficult in a reverberent room.
When I ran setup for my S2s the image was off. Everything seemed to pull to the right side. I went to the distance settings and added 0.2 feet to the right side and everything immediately snapped into focus, dead center.
 
M Code

M Code

Audioholic General
If you have been an XM user, was this during the time when they merged with Sirius? The Sirius channels I heard sounded like crap, IMO. The XM were OK, but I didn't really expect great sound- I used it for the content. The bad sound and their dropping of the main channels I listened to made it easy to drop them. Well, those and the price hike.
The hardware and broadcasting system for XM Radio was far superior to Sirius, the XM system used (3) satellites, and cell tower repeaters. However the primary advantage Sirius was its diversity for content, I have XM/Sirius in 1 of my vehicle but rarely use it but nice to tune in a target music channel without commercials. In concluding the satellite radio audio sonics are better than AM radio but still not audiophile quality....

Just my $0.02... ;)
 
Auditor55

Auditor55

Audioholic Chief
Psychoacoustics is not objective, it involves the way we perceive certain sounds rather than how our auditory system actually receives them, e.g., 4KHz tones sound like they're coming from the side, 8KHz sounds like its coming from directly overhead, regardless of which ear is receiving the input. It has nothing to do with flat frequency response acuity (or closely following the Fletcher-Munson, et al curves) or anything like that- the fact that 'psycho' is part of the word should make it obvious that the mind is involved.
"There are limits to perception and this varies greatly with every individual. Noises that can be heard by the average person are within the frequency range of 20 Hz to 20,000 Hz. "

Do you agree with the above quote?
 
S

shadyJ

Speaker of the House
The problem is that somehow a lot of audiophiles seem unable to decide whether they like the sound of a box without having first verified that what goes on inside the box fits their ideology.
This is so true, especially concerning loudspeakers. I have come around to believe that most audiophilia is a religious cult. These adherents are far more concerned about how the sound is created rather than the quality of the created sound itself. I think that audio gear should be looked at as a 'black box' in the theoretical sense; it has inputs and outputs, and the only thing that matters is how well the output matches the input.
 
B

Bruno P.

Audiophyte
(...) has a EE that didn’t get what’s been posted up by using Google.
That's not always an advantage. Several times I've sat here completely stuck over something. And then when I try googling if someone might have already done some work on this, it points me to my own stuff. Just google's kind way of saying "you're on your own, mate".
An amp that can reproduce 200K will be very unlikely to produce distortion in the audible range and an octave above.
If I understand your point correctly you're saying: 200 kHz in its own right may not be terribly relevant but it says something about what the amp will do in the audible range. Well if you know the precise circuit, perhaps. Otherwise not: how would you know that an unknown amp with 1% THD at 200kHz will do better than that at 1kHz? So then why try second guess at all? Why not simply measure directly, in the audible range, what it is you're trying to find out? If you use supersonic measurements as a kind of heuristic to make assessments, you need to understand quite a bit about the exact circuit before you can work backwards, from that supersonic data, to the expected result in the audible range. Some amps need a lot of extra bandwidth, some don't. Just test the audible frequency range and do so comprehensively. The point of making measurements is to assess a black box without having to pop the lid. If you measure parameters not strictly relevant to the intended usage, you still need to look inside the box to help interpret your measurement.
This is so true, especially concerning loudspeakers. I have come around to believe that most audiophilia is a religious cult. These adherents are far more concerned about how the sound is created rather than the quality of the created sound itself. I think that audio gear should be looked at as a 'black box' in the theoretical sense; it has inputs and outputs, and the only thing that matters is how well the output matches the input.
At least there is some wriggle room for discussion when it comes to speakers. Amps are the most boring subject: volts in, volts out, and if they are sufficiently alike so that nobody hears the difference between input and output, job done*. The only psychoacoustics involved is where it says that the range above 20kHz is going to be a lot less important than the range below 20kHz.
A speaker by contrast takes in a voltage (a one-dimensional signal) and puts out a 3-dimensional wavefront that bounces round the room. Finally, hopefully, your brain gets fooled into hearing a stereo image that corresponds to a wavefront that isn't pysically there. You need to ask: what should a speaker do to maximise the odds that the listener's brain will fall for the illusion. This makes it unlikely that a simple Platonic ideal speaker (a point source, for example) will be the best answer to that messy set of problems.
Of course, that doesn't mean it's a free-for all, quite the contrary. Besides pure engineering we've now also got to take acoustics and psychoacoustics into account. And of course, there are things we are sure of. A speaker still needs to have a flat on-axis response, a smooth (preferably flat) off axis response, and no gross distortions. That's always going to be the starting point. Other than that the spec sheet for a speaker is more a list of don'ts than a list of do's.

______
*Personal tastes and differences in perception don't even come into it. The closer the output resembles the input, the smaller the chance anyone can hear the difference, regardless of their musical predilections.
 
S

shadyJ

Speaker of the House
At least there is some wriggle room for discussion when it comes to speakers. Amps are the most boring subject: volts in, volts out, and if they are sufficiently alike so that nobody hears the difference between input and output, job done*. The only psychoacoustics involved is where it says that the range above 20kHz is going to be a lot less important than the range below 20kHz.
A speaker by contrast takes in a voltage (a one-dimensional signal) and puts out a 3-dimensional wavefront that bounces round the room. Finally, hopefully, your brain gets fooled into hearing a stereo image that corresponds to a wavefront that isn't pysically there. You need to ask: what should a speaker do to maximise the odds that the listener's brain will fall for the illusion. This makes it unlikely that a simple Platonic ideal speaker (a point source, for example) will be the best answer to that messy set of problems.
Of course, that doesn't mean it's a free-for all, quite the contrary. Besides pure engineering we've now also got to take acoustics and psychoacoustics into account. And of course, there are things we are sure of. A speaker still needs to have a flat on-axis response, a smooth (preferably flat) off axis response, and no gross distortions. That's always going to be the starting point. Other than that the spec sheet for a speaker is more a list of don'ts than a list of do's.

______
*Personal tastes and differences in perception don't even come into it. The closer the output resembles the input, the smaller the chance anyone can hear the difference, regardless of their musical predilections.
Agreed, and I should have mentioned that I was referring to frequency response and dynamic range as well. Dispersion types do throw a monkey wrench into the works, and bring in more personal preferences which I find to be neither right nor wrong. Some people prefer wide dispersion speakers and some prefer narrow dispersion which will have less interaction with the room. End-use acoustics are not even a normal consideration for recording engineers, so there isn't usually a 'right' answer there. I suppose there can be a wrong answer, for example a Bose style speaker which has way more late reflections in the sound than any artist or recording engineer would have ever intended.

edit: I forgot to put the bolded word in there!
 
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ryanosaur

ryanosaur

Audioholic Ninja
This is so true, especially concerning loudspeakers. I have come around to believe that most audiophilia is a religious cult. These adherents are far more concerned about how the sound is created rather than the quality of the created sound itself. I think that audio gear should be looked at as a 'black box' in the theoretical sense; it has inputs and outputs, and the only thing that matters is how well the output matches the input.
Fcuk, Shady... You just hit the M-F'n Nail on the head in my book!!!

If you are going to worry about the creation of the sound, you need to be a Producer. Otherwise, you need to make certain you are getting good source, good throughput, and good output; all in a manner consistent with the idea that good audio gear is about reproducing the "Recorded Event" in the most realistic manner possible.

:)
 
Gmoney

Gmoney

Audioholic General
3 years? Heck, my Denon AVP-A1HDCI lasted 8 years! :D
8 years uh? that would come to lets see.. get my Calculate out... umm $8.000 Divided by x into that, Subtract 365 days a year umm lets not forget at least two leap years, do umm comes to around umm $1.000 bucks x You lost a Lot of Your wife’s shopping for shoes money! Now lets take that same $8.000 bucks into todays Value of money umm X that with a Mutual fund investment at say 9% and that comes to umm, If I where you I’d go out and by some AFLAC insurance cause if the Miss’s really finds out just how many new pair of shoes she could have had you my be walking with a pair crutches. :p;)
 
Gmoney

Gmoney

Audioholic General
Agreed, and I should have mentioned that I was referring to frequency response and dynamic range as well. Dispersion types do throw a monkey wrench into the works, and bring in more personal preferences which I find to be neither right nor wrong. Some people prefer wide dispersion speakers and some prefer narrow dispersion which will have less interaction with the room. End-use acoustics are not even a normal consideration for recording engineers, so there isn't usually a 'right' answer there. I suppose there can be a wrong answer, for example a Bose style speaker which has way more late reflections in the sound than any artist or recording engineer would have ever intended.

edit: I forgot to put the bolded word in there!
@shadyJ, So that’s Bose speakers Secret, they been Cheating the whole time and getting away with it and laughing all the way to the bank. The Bose wave uh? On a more Serious note, @ Bruno, ShadyJ, you two are posting up some Excellent post to read! Better than anything I’ve found on the internet lately.
 
highfigh

highfigh

Audioholic Overlord
"There are limits to perception and this varies greatly with every individual. Noises that can be heard by the average person are within the frequency range of 20 Hz to 20,000 Hz. "

Do you agree with the above quote?
The range you posted is the supposed 'normal' hearing acuity range for humans, at some point in their life, but it refers to the physical stimulus of our hearing mechanism, not how we perceive the sound and that's where psychoacoustics comes in. Can we localize all frequencies as coming from the speakers? No, because as I wrote, some frequencies seem to be coming from someplace that would be impossible even when the listener/patient is wearing headphones.
 

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