Yep, good summary, that's why I have to disagree with A.wayne. If anything, some noise would help to bring the faintest detail out, rather than obscure it.
There is another reason why some noise in the signal might contribute to improvements, that is on the side of the sound source. No transducer is completely devoid from hysteresis. Keeping it ever so minutely in motion by random noise will also randomize the distortions caused by hysteresis, or in other words, decouple them from the signal.
The first para is based on accepted science, the second on my conjecture, so take it with a grain of salt. At any rate, for me it must be part of the explanation why ClassD sounds better than it should.
vac
Japanese music
The Japanese wording I gave was too general . This music approximates . However more installments would be used and one artist . A bit off beam from the discussion . Hope some take a look . FAL does not conform to some accepted standards ( frequency response dips , mic too close , standard test , standard problem I would say ) . When listening they seem to contradict the graphs .
Eitetsu Hayashi ? Bolero part1 ???????? - YouTube
The Japanese wording I gave was too general . This music approximates . However more installments would be used and one artist . A bit off beam from the discussion . Hope some take a look . FAL does not conform to some accepted standards ( frequency response dips , mic too close , standard test , standard problem I would say ) . When listening they seem to contradict the graphs .
Eitetsu Hayashi ? Bolero part1 ???????? - YouTube
The noise floor is already delivered by the recorded medium, adding more via the electronics is good ...?
Err no cant buy into that ....
FAL
I tried a standard almost blameless amp with them ( damping factor circa 90 ) . They were fantastic . FAL agent was stunned and said if only his friend would listen to transistor amps . It was mostly the same sound .
I take your point . Fostex are interesting if trying current drive . The are fine in voltage drive also .
The amp was my own variation of the Hitachi MOS FET design with some care taken over the VAS . I tried Szikai pairs and FET in a variation recently and was stunned to find I preferred the Szikai . The measurements were very slightly different . The sound was surprisingly similar . I stuck with FET's as I like the simple biasing ( 100 mA is a good place to start ) Exicon if wondering .
I tried a standard almost blameless amp with them ( damping factor circa 90 ) . They were fantastic . FAL agent was stunned and said if only his friend would listen to transistor amps . It was mostly the same sound .
I take your point . Fostex are interesting if trying current drive . The are fine in voltage drive also .
The amp was my own variation of the Hitachi MOS FET design with some care taken over the VAS . I tried Szikai pairs and FET in a variation recently and was stunned to find I preferred the Szikai . The measurements were very slightly different . The sound was surprisingly similar . I stuck with FET's as I like the simple biasing ( 100 mA is a good place to start ) Exicon if wondering .
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HYPEX
I think Hypex have proven the point about class D . They use 5532 ( or 4 , it was a couple of years ago ) . We replaced some and were surprised how good the 5532 is . As they are SMD it is a difficult task . The op amp can have a separate supply . Try it . I think they do have slight bus pumping issues and are better in bridge perhaps .
Genesis in USA have a very nice version .
I think Hypex have proven the point about class D . They use 5532 ( or 4 , it was a couple of years ago ) . We replaced some and were surprised how good the 5532 is . As they are SMD it is a difficult task . The op amp can have a separate supply . Try it . I think they do have slight bus pumping issues and are better in bridge perhaps .
Genesis in USA have a very nice version .
DF96, frankly, I don't really care what you or anyone else uses anywhere. That is a good op amp, however, it was a killer a long, long time ago, when it first appeared in the late 70ies.
Since then, over the last 30 years, I believe we've all learnt much and new, sonically superior (in my view) op amps have appeared. I don't even know what the current fashion in op amps is, nor do I care, because I do not run with the "in" crowd.
But I have followed up on some which appeared to be promising, notably those which offer good speed, but low HF distortion; I find that too many "in" op amps produce inordinate amunts of HF distortion even if they shouldn't. In the end, I do keep a stock of four op amps I sometimes use for audio, although my preferences still rung strong towards the discrete circuits.
I think I better not name them, else I might be accused of advertising, since they all come from the same manufacturer. Three I know to be results of Walt Jung's involvement (to what extent I don't know), the fourth is an older one, and I don't think he worked on that one (but I could be wrong).
So you go right ahead and use whatever you feel is worth using, but do not each and every time take offence when somebody says something you don't agree with.
So I should not take offence when someone has a dig at UK engineers and their alleged worship of NE5532, or a dig at all PhDs and their alleged lack of practical skills, or when those who understand and believe standard loop theory are suggested to have been off the planet for so long that they have never heard of a disputed paper by Otala? Should I just ignore such nonsense?
I may have heard the phrase before, but wasn't aware of what it meant. With the word resonance, it sounds a little bit new age, but it's not:
That description sounds quite familiar, in dithering of A/D's (which it mentions) and bit reduction within the digital domain, and in ac bias in magnetic tape recording (which it does not mention). I'm surprised to find it to be so recent:
This National Semiconductor app note on dither is dated 1992, but has references that go back to the 1960's and 1950's:
http://www.ti.com.cn/cn/lit/an/snoa232/snoa232.pdf
The nonlinearity of magnetizing a domain is both large and has a large amount of hysteresis. The bias signal fixes both of these. I wonder how well an ultrasonic noise source would work compared to the single-frequency bias signal used in tape recorders.
There are many nonlinear devices that might benefit from the addition of either a constant single-frequency "ac bias" signal or a (probably noise-shaped) "dirher signal," such as audio transformers (though they are often used, especially at mic level, BECAUSE of the distortion they generate), And while we're at it, power amplifiers as well.
Surely someone has tried this. Class D is kind of like this, but that is "linearizing the extremely non-linear" for the sake of electrical efficiency. Could "ac bias" or "dithering" improve a power amplifier that is already "almost perfectly" linear?
This is my take on the 5532-34. As an op amp, made about 35 years ago, it is pretty good. However, I did, for myself, a direct A-B test against one of my more modest discrete op amps, and I HEARD a difference, yet the measurements would not show much. I did this test 1/3 century ago.
Later, we tried different BRANDS of 2N5534, and found differences, sonically.
Finally, we tried a mod based on a Siliconix app note that substituted the first stage of the 2N5534 with a Jfet pair. This WORKED! In fact, it worked so well, that my technician got orders for this mod from Dave Wilson to put in his equalizers that he sold with his WAMM speaker systems for some years. And so it goes!
Later, we tried different BRANDS of 2N5534, and found differences, sonically.
Finally, we tried a mod based on a Siliconix app note that substituted the first stage of the 2N5534 with a Jfet pair. This WORKED! In fact, it worked so well, that my technician got orders for this mod from Dave Wilson to put in his equalizers that he sold with his WAMM speaker systems for some years. And so it goes!
Why not? I ignore quite a bit of nonsense here and elsewhere, and I'm still alive and well.
Or should I mimick you, and turn very angry when bashed on the head by Cordell?
Are you suggesting that the PhDs are blameless?
"Standard loop theory" - you mean the latest news, from December 1930?
Give it a break, DF96, agreeing or disagreeing is one thing, but "taking offence"? If you are so easily offended, what the hell are you doing on any public forum at all?
We're not here to kill each other, surely. But before you challenge me to a meeting at dawn with my two referees, be advised that I earned 5 (five) army awards for sharpshooting with rifles and automatic pistols. Which is a sick joke unto itself, since I despise firearms.
So - calm down, think to yourself: "This bloke is crazy!" and I'll agree with you. However, while occasionally really crazy, I am not stupid.
Class D
Genesis GR 180 - Hypex-equipped digital power amplifier - [English]
I fear class D as it means I cannot throw an amp together from a half-backed ideas any more . Most of my ideas are half-baked and I am not ashamed to admit it . I was mostly saying 5532/4 as I usually keep away from it . 5534 is a posh 741.
I do think apart form TV's ( shipping costs ) class D advantage are not great if they exist at all . My friends use class G when they need to and it has many advantages over D. It isn't called G , that's what it is .
I was one of the first people in the world to hear class D in 1979 . I was to be a representative of Sony . It never happened . On my advice a Linn Naim System was taken to Japan ( bought at Grahams ) . This became Sony Esprit . This was only because my boss was very chummy with the video division and it was a little job for the kid . The engineer said to me something . We think it sounds good because it has choke ( not my typo this time , his words ) . He smiled and said maybe why tube amp sound good ?
To be clear I like the old ways . I was quoted by David Price as saying " Nige says CD's are good to hum to whilst vacuum cleaning " . Oh I wish I had .
[
CLass-D , The camels dangles .......
Genesis GR 180 - Hypex-equipped digital power amplifier - [English]
I fear class D as it means I cannot throw an amp together from a half-backed ideas any more . Most of my ideas are half-baked and I am not ashamed to admit it . I was mostly saying 5532/4 as I usually keep away from it . 5534 is a posh 741.
I do think apart form TV's ( shipping costs ) class D advantage are not great if they exist at all . My friends use class G when they need to and it has many advantages over D. It isn't called G , that's what it is .
I was one of the first people in the world to hear class D in 1979 . I was to be a representative of Sony . It never happened . On my advice a Linn Naim System was taken to Japan ( bought at Grahams ) . This became Sony Esprit . This was only because my boss was very chummy with the video division and it was a little job for the kid . The engineer said to me something . We think it sounds good because it has choke ( not my typo this time , his words ) . He smiled and said maybe why tube amp sound good ?
To be clear I like the old ways . I was quoted by David Price as saying " Nige says CD's are good to hum to whilst vacuum cleaning " . Oh I wish I had .
[
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Exactly - that's how it goes, with each and every component, no exceptions.
Thecnological progress is a game of leapfrog, you are the best for about 3 months, until somebody else produces something even better.
Good point on brands, John, I fforgot to mention that, although of course, exactly the same applies to all other op amps made under licence.
Let's build on this note.
It's my experience that no matter what the Data Sheet says for typical linear op amps, I have yet so see/hear one which does not show marked improvements when it is built upon with a current booster pair of transistors. No fancy circuits, just a simple current booster.
NEVER fails to produce better sound, although the improvement can be from small to rather impressive, depending on the chip. And all it takes is a pair of something quite mundane, like say MPSA 06/56, which you can pick up almost anywhere for a ridiculous price.
Try AD817 (827 double) with this mod - it will almost literally blow the NE off the table.
It was you who first used the word "offence". It seems to me that you wish to have the freedom to insult whoever you like, and then accuse them of taking offence when they protest. I started this as a technical discussion. It was you who started making personal remarks aimed at entire classes of people.dvv said:
So let's cool it. Please try to answer technical criticisms with technical rebuttals, not insults or quotes from supposed gurus.
OP AMP Booster
I use a Szikai pair without feedback as current booster and can use that for many things . If I put feedback on it is interesting as the two modes are not dramatically different and measure about the same ( - 80 dB 1 kHz ) . I don't find inverting mode sounds dramatically better and needs more driving . Also I don't find inverting mode dramatically more stable
We should have a competition of who can make a 741 sound best .You can add JFET's etc. I bet with care it can be done .
I am fairly certain I know who first used the class A trick and in was on a current dumping amp at Oxford University . I leant that trick in 1975 I think .
The idea of putting 10 K to the negative rail was because it was thought " philosophically " the -V e rail was better . I note LT have it on one of their best op amps as a recommendation ! Guess it does no harm and they are hedging their bets ?
5534 is very easily made unstable and is not happy with gains of less than 10 . It can be compensated . We still felt it doesn't make a good buffer even when stable .
MC 33078 is a good version for someone who wants a better 5532 ( cheap in other words ) and doesn't need 60 mA . No good for Self amp perhaps . Have read the tweaks suggested for that . Douglas will go mad . It's blameless , stop doing that . I haven't read his comments so forgive if I am off target . Also, well done . I had thought of it and thought ....NO . Too mad even for me .
Brits are very good at make do and mend . Take the Mosquito . That can not possibly work .
I suppose a good op amp is an oxymoron .
I use a Szikai pair without feedback as current booster and can use that for many things . If I put feedback on it is interesting as the two modes are not dramatically different and measure about the same ( - 80 dB 1 kHz ) . I don't find inverting mode sounds dramatically better and needs more driving . Also I don't find inverting mode dramatically more stable
We should have a competition of who can make a 741 sound best .You can add JFET's etc. I bet with care it can be done .
I am fairly certain I know who first used the class A trick and in was on a current dumping amp at Oxford University . I leant that trick in 1975 I think .
The idea of putting 10 K to the negative rail was because it was thought " philosophically " the -V e rail was better . I note LT have it on one of their best op amps as a recommendation ! Guess it does no harm and they are hedging their bets ?
5534 is very easily made unstable and is not happy with gains of less than 10 . It can be compensated . We still felt it doesn't make a good buffer even when stable .
MC 33078 is a good version for someone who wants a better 5532 ( cheap in other words ) and doesn't need 60 mA . No good for Self amp perhaps . Have read the tweaks suggested for that . Douglas will go mad . It's blameless , stop doing that . I haven't read his comments so forgive if I am off target . Also, well done . I had thought of it and thought ....NO . Too mad even for me .
Brits are very good at make do and mend . Take the Mosquito . That can not possibly work .
I suppose a good op amp is an oxymoron .
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Nigel, do try an OPA 275 dual op amp (I think the single versions is 177, or some such).
I think you'll like it, it's everything you can expect from a well made product. Its settling time (90->10%) is about 7 or 8 times shorter than in case of the NE. You hear more space, both up to down and front to back.
Over the years, I found out by simple trial and error, in conjunction with various owners of Marantz CD players, that you simply cannot do better in then with the 275. Not even wildly expensive, out-of-this-world spec op amps could do batter, at least those that I have had the opportunity to try (mostly by Burr-Brown, some by Analod Devices and National Semi.).
The only time it wasn't the best was in my own Yamaha CDX 993 player; AD 826 did better, so it's still there.
Super chips
I always fit chip holders in prototypes so as to do tests . I have in front of me now a phono stage and it has fixed chips . I have put right an error in the LF . I have requested a chip holder version as I want to design the next phase . Wish I had it before this . . Doubtless it denies an ultimate test a chip holder however ........ . I know a lot of tweaky people and get hands fulls of their cast offs ( carefully cast off ) .
I often have things put my way where we aspire to 5534 . We sometimes use very nasty op amps because they go rail to rail and are safe even to go below rail . Zener diodes are very good to prevent that as they will go through the origin at lightning speed ( mains / car transients ) . Zeners are noisy so not always an answer . I am expected to do a good job even if the 4 chip op amp costs 20 cents US . I love it .
My greatest disappointment is in super chips . As said JFET's sound good . I dug out a LF351 which almost is a JFET 741 . It sounded much better than it measured . The one below is one I am unsure about . I will persist as it looks so good on paper . Remember I am Hawksford in things like this . I will try some video op amps soon as they look close ( 5 V 0.9 nV 1500 MHz - 89 dB distortion u = 1 ) . Not sure you can have all of that in one device . However probably you can . That is from memory . Don't say 5 V no good . It can be if used with a little imagination . Some even have audio imfo . About $3 usually . SMD . The ones I see are conventional as normal op amps or can be used that way . I have a hunch the one below is a video amp tweaked a bit . Not unknown to do that . The Dynaco input 7199 was a tweaked TV tube .
LT1115 - Ultra-Low Noise, Low Distortion, Audio Op Amp - Linear Technology
I had a discontinued super chip . Sorry number escapes me . As near zero distortion as is possible , J FET . It neither sounded good nor bad . It just was incredibly different . It was for want of a better word dignified .
I always fit chip holders in prototypes so as to do tests . I have in front of me now a phono stage and it has fixed chips . I have put right an error in the LF . I have requested a chip holder version as I want to design the next phase . Wish I had it before this . . Doubtless it denies an ultimate test a chip holder however ........ . I know a lot of tweaky people and get hands fulls of their cast offs ( carefully cast off ) .
I often have things put my way where we aspire to 5534 . We sometimes use very nasty op amps because they go rail to rail and are safe even to go below rail . Zener diodes are very good to prevent that as they will go through the origin at lightning speed ( mains / car transients ) . Zeners are noisy so not always an answer . I am expected to do a good job even if the 4 chip op amp costs 20 cents US . I love it .
My greatest disappointment is in super chips . As said JFET's sound good . I dug out a LF351 which almost is a JFET 741 . It sounded much better than it measured . The one below is one I am unsure about . I will persist as it looks so good on paper . Remember I am Hawksford in things like this . I will try some video op amps soon as they look close ( 5 V 0.9 nV 1500 MHz - 89 dB distortion u = 1 ) . Not sure you can have all of that in one device . However probably you can . That is from memory . Don't say 5 V no good . It can be if used with a little imagination . Some even have audio imfo . About $3 usually . SMD . The ones I see are conventional as normal op amps or can be used that way . I have a hunch the one below is a video amp tweaked a bit . Not unknown to do that . The Dynaco input 7199 was a tweaked TV tube .
LT1115 - Ultra-Low Noise, Low Distortion, Audio Op Amp - Linear Technology
I had a discontinued super chip . Sorry number escapes me . As near zero distortion as is possible , J FET . It neither sounded good nor bad . It just was incredibly different . It was for want of a better word dignified .
The noise floor is already delivered by the recorded medium, adding more via the electronics is good ...?
Err no cant buy into that ....
Hi a.wayne,
In this sense you might be right. The point is for noise to raise a signal above the threshold of detectability, it is best to keep the noise signal itself under this threshold. It is the addition of these two signals that should peak above the threshold. Recording media may already offer more than enough noise at it is.
Btw, as BenB mentioned '81 for the invention of the term stochastic resonance, it was known well before that. I dallied around a bit with neural networking in the early '80's, and this trick was known then. A better term in my mind would be 'stochastic bumping', because that what the noise actually does with the signal.
vac
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