A question for the analog Gurus

Discussion in 'General Electronics Chat' started by Shagas, Jun 1, 2013.

  1. Shagas

    Thread Starter Active Member

    May 13, 2013
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    Greetings!

    There is a thing that has been bugging my mind for quite a while now so i'll elaborate on it and hope that you guys won't get bored while reading through it.


    I've been into quality sound for a few years now and my workbench/station is equipped with a pair of Active Studio monitor speakers which are apparently supposed to produce high quality 'unbiased' sound and flat frequency response, which they do .

    I've recently unscrewed the back of my M-Audio BX5's to take a curious look on the insides and the amplifier circuit.
    I've been playing around with electronics for about half a year now so i'm still a newbie... but upon examination of the main pcb I expected to see power BJT amps fueling the sound but instead what I found is some wierd many-legged IC attached to the main heatsink . After looking it the datasheets I discovered that It was an integrated audio amplifier which left me scratching my head.


    Anyway getting to the point , my question is : From the perspective of sound quality ,frequency response , accuracy, distortion % , fidelity etc... will an integrated (Monolythic ? ) power-amplifier IC perform better than the classic 'Passive speakers and an amplifier ' which was designed with multiple stages , all kinds of stabilisation circuits and all that jazz, 'made by hand' ..if that makes any sense . For example:

    View attachment 56209
    (just found some random amplifier picture on google)

    I Don't have the equipment/knowledge to test signal fidelity percentages or distortion percentages myself and I can't type this post into google and expect a processed answer (maybe in 15 years from now ) so i'm asking you guys if anyone here has any experience with building a high quality audio power amplifier


    Also, when a company designs an audio amplifier for some application for example a Stereo set or whatever do they design it themselves or is there a 'Best amplifier circuit schematic' available somewhere that everyone knows about and uses to build amplifiers ? A schematic where the components and values are arranged in a 'perfect' that cannot be improved in any way that we know of to get better results .

    *****

    The monitors that I use are
    M-audio BX5
    and
    Behringer Truth B1031A
     
  2. Shagas

    Thread Starter Active Member

    May 13, 2013
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    my bad I posted the thread twice by accident , trying to find how to delete it :)
     
  3. Shagas

    Thread Starter Active Member

    May 13, 2013
    802
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    Can a mod please remove one of the double threads that I just posted ?
    My pc screwed up
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    The truth of audio is that the loudspeakers introduce far more distortion than all of the electrical components combined. Second truth: no loudspeaker can ever produce sound as clean as very good headphones (like Sennheiser) for a wide array of reasons:

    The speaker has to move large volumes of air and the mechanical transducers are adding a lot of distortion. More important, the characteristics of the surroundings greatly affect speaker sound.

    I believe "active" speakers just mean there is an amplifier built in, doesn't actually say anything about the sound quality.

    hate to break the bad news, but integrated power amps have "all that jazz" built into them too, no magic inside. They are generally a cheap way to make decent sound, but certainly not hi-fi.

    Yes, I do... and I would certainly never do it again. There are such good receivers and amps available for such low cost it makes no sense. And there are a lot of protection circuits you would need to add to the basic amplifier that is built in to a finished amp.

    depends on the company and application. They typically buy the cheapest design from any of a number of Far East sweat shops. There is no "best circuit design".
     
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  5. crutschow

    Expert

    Mar 14, 2008
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    I would say that, in general, the audio IC power amps give good low distortion sound, if you stay within their power limits. That is because the designer can easily include all the bells and whistles required for a good audio amp because theirs little cost penalty in adding them to an IC circuit design. Also, all the active parts tend to be inherently matched so the biasing of the stages (particularly the output stage) remains stable.

    For example Siegfried Linkwitz, a well know audio designer (helped develop the Linkwitz-Riley Crossover filter used in many high end speakers), has designed some very high end speaker systems and in one of them, he used the LM3886 audio amplifier to power the active speaker system. Since his designs use only the best components I believe that's sufficient reason to believe that IC audio amps can be just as good or better than any discrete designs.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    That may well be true, but the type of distortion heavily affects the perception of the distortion. I believe certain types of amplifier distortions, even though it may have a much lower numerical percentage, are more noticeable than the type produced by speakers. For example, I have some old, middle-of-the-road JBL bookself speakers and, using them with the same program source, I can readily tell the difference between my old Sony high-end receiver amplifier and my even older Dynakit Stereo 120 basic solid-stage amp (which I built nearly 50 years ago). The sound with the Sony lacks the clarity and smoothness compared to the sound with the Dynakit. I think that may be due to small values of crossover and/or third harmonic or IM distortion from the Sony that the ear readily perceives.
     
  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Maybe, but I measured the THD coming off the bass drivers in some "high end" speakers once upon a time (late 70's) using our schools anechoic chamber and some very high end equipment....

    They had THD levels in the range of 3% to 5%. That is horrendous. The awful distortion from speakers is the reason for listening fatigue.

    I know that "odd order harmonics" are more "annoying" but it's still hard to believe speakers are not the main offender. In reality (here comes heresy) people just get used to the sound their speakers produce along with all the coloration and don't like true sound.

    My brother's car had a bumper sticker that said:

    Clean air smells funny.

    Well, true sound without the wall resonance "sounds funny" to somebody who is used to the same sound ..... I don't doubt that the two amps sound different, just not sure which one is closer to reality. One probably just sounds better with the speaker's particular resonances. Even more likely is the Sony needs some of its caps replaced as they have dried out from old age.
     
    Last edited: Jun 1, 2013
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    It's definitely good enough for most applications and orders of magnitudes cleaner than the acoustic drivers most people listen to.

    3886 is a good one. Better than the typical low end junk used for car applications and cheap stereos.

    http://www.ti.com/lit/ds/symlink/lm3886.pdf
     
    Last edited: Jun 1, 2013
  9. crutschow

    Expert

    Mar 14, 2008
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    Certainly 3-5% distortion seems horrendous, but most of that in a bass speakers is even harmonic distortion which just adds harmonics an octave higher, so the sound is a little "brighter" which generally doesn't sound bad.

    I think if you heard the difference between my two amps you would immediately know which sounds better and I don't think that's due to any speaker "resonances". It could be due to old caps in the Sony but I doubt that. For one thing, both channels sounded the same and it seems unlikely that the capacitors in both sides would have aged identically.

    Incidentally my criteria for good sound is how close to "live" does it sound, not what I'm used to.
     
  10. Metalmann

    Active Member

    Dec 8, 2012
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    For the last several years, I've been using the M-AUDIO-SP-5Bs, for my home studio. The manual breaks them down to this:

    "In order to generate ultra crisp, powerful sound quality, there are two separate
    power amplifiers inside the SP-5B, to drive the Woofer and Tweeter drivers
    separately; as a (high-end Bi-Amp structure).
    The power delivered to the woofer
    driver, at a rated distortion is 42W, and 36W is delivered to the Tweeter." That says there is 78 Watts, instead of the 75 advertised.:confused:


    They are no comparison to real, professional, studio monitors.

    We used headphones to record in those studios, but when you listen back in the control room....no comparison.

    So much of the music business is HYPE. Whoever has the best hype, makes more money. :D;)

    As listening/hearing, is subjective; who is to say whose monitors are better than others?:cool:

    Nowadays, for recording at home; I use the Sennheiser HD555 headphones. With their baffles removed....

    Playback is through both monitors, and headphones. Whichever sounds better at the time.;)
     
  11. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I use HD580.
     
  12. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Since I only listen to recorded music, it would be impossible for me to make that comparison since I wasn't there when it was recorded. And the guy who "tweaks up" the master puts so much spin on the equalization to "sweeten" the recording I doubt if anybody ever heard the actual original sound. The trick is always to juice it up so it sounds like what people like.... any resemblance to reality is purely coincidental.
     
  13. crutschow

    Expert

    Mar 14, 2008
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    By "live" I don't mean what it may have sounded like in the studio, I mean does it sound realistic -- do pianos sound like pianos, do cymbals sound like cymbals, are male voices free of booming, etc. That's independent of what they do in the studio. So what's your criteria for good sound besides measured distortion?
     
  14. Shagas

    Thread Starter Active Member

    May 13, 2013
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    I wish the opposite were true :/ . I'm using a pair of Sennheiser HD-25-II
    and although the sound is crisp and accurate it's still more pleasant to listen and mix through my monitors because of the room acoustics and stereo imaging.

    Thx for all the other info aswell!
     
  15. Shagas

    Thread Starter Active Member

    May 13, 2013
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    That depends more on the recording/mastering and the room acoustics than it does on the actuall speakers In my opinion
     
  16. Shagas

    Thread Starter Active Member

    May 13, 2013
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    By the way... Why is direct coupling used in HIFI equipment rather than capacitor coupling ?
    Does the freq-response degrade with capacitor coupling ?
     
  17. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    That question calls up something closer to religion than science. Some claim to be able to hear the "degradation" in sound quality caused by low quality caps in the signal path. I use poly film caps just to be sure, but the evidence of "improvement" is sketchy at best. I would not use aluminum electrolytics because they dry out with age and become inductive. Solid Tantalums are fine. Ceramics are probably fine as well but some claim the "piezo" effect ruins the music sound.
     
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  18. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    That's the whole point: there is no scientific criteria for "good" sound since people never agree on what it is or what produces it. Good sound is whatever sounds good to you.
     
  19. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Exactly. mastering is and always has been a "silly guess" at how to bend a recording so it sounds good to most people on a typical system. During the LP (turntable) days, they intentionally brightened the high frequencies to compensate for weak high end. IMHO, that is the reason that purists screamed that CDs sounded too "bright" and "harsh" compared to vinyl when they first came out... they used the old boosted masters to make the CDs. A lot of masters also had the bass boosted to compensate for the weak bottom end of most speakers, and simply because people like the sound of bass. Cheap speaker designers always design the resonance so it will "boom boom" the low end and sound like it has "more bass". Everybody has heard the nitwit salesman switching between speakers telling the customer "this speaker has more bass!" And they always buy that one.

    The only "pure" recordings made back in the day was called a direct-to-disc cut where the performance drove the master cutting head directly. My brother had some of those for live classical performances. They still had the RIAA compression/expansion that all phono recordings have but no equalization. Those records were EXPENSIVE. With no master tape, the one master that was direct cut stamped vinyl until it was done and that was it... very limited edition.
     
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  20. #12

    Expert

    Nov 30, 2010
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    That's exactly what I was thinking. This kind of conversation can become heated and opinionated very quickly.

    Good audio has aspects of both science and art. I wouldn't be surprised to find that people have dueled at dawn over what constitutes "the best audio". If you want the best audio for you, study, build, and learn. You will probably learn that teams of people have spent decades building better amplifiers than you will achieve in only one lifetime. If you're smart, you will learn what makes it work for you, then go buy something that excels at what YOU believe is the best audio.
     
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