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Thread: Amplifiers are more significant than you may think!

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    Amplifiers are more significant than you may think!

    Good morning (French time),

    I am a JBL listener since years (4311 - 4320 - 4333 and 4355) and I am reading this forum since several months now.

    I also had several home made ALTEC speakers made of 411-8A woofer, 511 or 811 horns with a 806-8A driver.

    I noticed quite a lot of complaints about lack of this, lack of that, willing to compare the dynamic and sound image of a 4343 / 4355, and so on.

    I must say that I am working since 25 years in the amplifier market and I begin to have some knowledge’s about what an amplifier is.

    You may not agree with me but I always thought that the quality of an amplifier is not only ascertained by sophisticated laboratory control methods.

    One has to hear his performances, the human ear being the best of judges.

    A sound is not only built up with technical specifications.

    The only numbers I trust in are the signal to noise ratio (> 100 dB), the CMRR if you have a balanced input (> 80 dB) and the peak power!

    Other numbers are just useless.

    About distortion:

    Add the distortion of the speaker, of the room and of your ear and you will be close to 3-4%. In such a case how important is the distortion of an amplifier? Nuts …

    Damping factor:

    I am not the author of this theory, but if the damping factor is > then 17, what ever the number is it has no significant meaning. Never forget that the damping factor is calculated at the “bottom” of the amplifier and do not include the wires and the impedance of the speaker at low frequencies. As a bass reflex speaker has a bigger impedance at low frequencies, the damping factor will raise immediately.

    When an amplifier manufacturer argue that his amplifier has an enormous damping factor at 8 ohms and this is very good for bass restitution, and his amplifier handles easily a 2 ohm impedance, just divide by 4 this damping factor …

    This is a 100% commercial number.

    All those numbers and others do not make the sound quality!

    There are things everybody ignores as I do, and they make an amplifier sound good!

    The use of one brand of capacitors, the use of a type of capacitors, such quality of resistors, and so on is the basis of known things in the audiophile area.

    After that, changing one component for an other can make an amplifier sound great, better or worse!

    Let me give you several examples:

    Change the bridge of your amplifier and the bass response can change radically; I did it just by changing a 20A bridge for 25A bridge from the same manufacturer and same bridge family (as I use a twin bridge in each channel for a 150W amplifier there is no relation between the needed amperes and what the bridges can deliver).

    I made the same with an other brand and other models, it did not work the same.

    Removing a limiter circuitry will enhance the micro information in the mids and high frequencies,

    Changing an input potentiometer from one brand to an other, even if this potentiometer is set at 10 (wide open) it will change the tonality of your amplifier,

    Since a year time that I now have the 4355 JBL speakers I made so many changes on my amplifier (same schematic, AB class, quasi complementary bipolar output transistors) I have now (and the job is not over and never will be) a new sound system:

    I have all the low bass I was looking for,
    I have more low mids,
    There is no more agressivity (is it the good word) in the mids,
    I have much more information in all the frequencies,
    The high are also dam smooth and even more precise.

    All what I did was to got the good settings in my amplifier.

    This is perhaps the beginning of a long thread and I think it will be helpful for all of us and I hope I did not bore you too much with this message!

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    Re: Amplifiers are more significant than you may think!

    "About distortion:

    Add the distortion of the speaker, of the room and of your ear and you will be close to 3-4%. In such a case how important is the distortion of an amplifier?"


    Quite... garbage in, garbage out. If you need more information on the relevance of amplifier distortion reference Dr. Matti Otala's work.

    "Damping factor:

    This is a 100% commercial number.


    Yes and no, I think I understand what you are getting at, but it still "tells" you the output impedance of the amplifier and that can be a useful number. You may have noticed also that JBL often uses a parallel resistor across many of their bass drivers to "help" present a more linear load to a driving amplifier.

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    Re: Re: Amplifiers are more significant than you may think!

    [QUOTE]Originally posted by Giskard

    About distortion:

    Quite... garbage in, garbage out. If you need more information on the relevance of amplifier distortion reference Dr. Matti Otala's work.

    I do not agree! No one can hear the difference between 0,1% and 0,00000001% of distortions!
    It is the same for the memory of some components and so on…

    Those are just arguments sellers try to “sell” you as being as a critical number, they are just fooling us.

    If those numbers were that important, why do bulb amplifiers sound so smooth (perhaps a lack of dynamic and punch in the bottom note)!

    Damping factor:

    Yes and no, I think I understand what you are getting at, but it still "tells" you the output impedance of the amplifier and that can be a useful number. You may have noticed also that JBL often uses a parallel resistor across many of their bass drivers to "help" present a more linear load to a driving amplifier.

    Once again I do not 100% agree with you.

    It is a number that must be treated very carefully.

    Having a big damping factor can improve the bass transient and linearity but it does not mean that if an amplifier has a big damping factor it will give you big bass.

    Once again it is quite a lie the way many amplifier manufacturers are printing their characteristics.

    All of them claim to have the best numbers and a great sound quality.

    Sound quality is never a “translation” of good numbers, if it was all amplifiers would sound great, unfortunately a lot of them, even big brands sounds …

    Very little play good music.

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    Re:Amplifiers are more significant than you may think!

    I guess you are viewing all this from a Marketing standpoint and are fed up with the Marketing hype?

    Yes, there does come a point where the published distortion figures are meaningless in real world application. However, amplifier distortion is a very real phenomenon, the various types of distortion, negative feedback, etc. Seriously, if you read various articles from/about Dr. Otala you might find topics of interest. He really didn't waste his life's time on amplifier distortion just so other people could come along and say "In such a case how important is the distortion of an amplifier? Nuts …"

    That said, I agree with you that "selling" an amplifier based solely on the virtue of some distortion figure some Marketing person read off an engineering report they had no business seeing anyway is pretty dubious

    "It is a number that must be treated very carefully."

    Why? It's not spooky or anything, despite what Marketing would have us believe. It's just a ratio. No Holy Grail, no Blessing from the Pope, just a ratio of two numbers, and quite probably meaningless to 98% of the people who read it...

    "All of them claim to have the best numbers and a great sound quality."

    Economic Capitalism?

    "Sound quality is never a “translation” of good numbers, if it was all amplifiers would sound great"

    I'll buy that!

    Obviously we're on different pages though. I have zero interest in what the Marketing folks are churning out of their propaganda machines. Damping factor, or even better, output impedence, is real, and is valid, but I personally couldn't care less what some Marketing person is doing with the numbers.
    Last edited by 4313B; 06-19-2003 at 10:10 AM.

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    Re: Re:Amplifiers are more significant than you may think!

    [QUOTE]Originally posted by Giskard

    Obviously we're on different pages though. I have zero interest in what the Marketing folks are churning out of their propaganda machines. Damping factor, or even better, output impedence, is real, and is valid, but I personally couldn't care less what some Marketing person is doing with the numbers.

    In such a case, what numbers "sounds" good for you, and why will they make an amplifier sound well, fine, great, gorgeous?

    I have just built two amplifiers with exactly the same basis; the only differences will be the bridges, balanced input IC (INA134 instead of OPA27GP), potentiometer - one from somewhere and the other one from ALPS, and different input transistors (2SA1085 instead of BC490B).

    What I can say is that the measures are the same, but what I hear is completely different!

    One amplifier sounds if it was raining cats and dogs, the other sounds as if it was full sunshine.

    I am “bargaining” with an international audio magazine to get them test benched and a full report printed from their chief engineer, after that they will lend them to a studio and ask them what do they feel out of those two amplifiers.

    That is why, numbers are just numbers …. And none of them can explain why this amplifiers sounds so good or so bad!

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    Re: Amplifiers are more significant than you may think!

    Ok, so you ARE bummed about the fact that "numbers sell" amps then

    I guess now you know how many engineers and designers feel when their "numbers" might not appear as "good" as a competitor's yet their product sounds "better".

    As for what numbers sound good to me. I don't listen to numbers. I listen to designers and engineers such as yourself who say things like:

    "I have just built two amplifiers with exactly the same basis; the only differences will be the bridges, balanced input IC (INA134 instead of OPA27GP), potentiometer - one from somewhere and the other one from ALPS, and different input transistors (2SA1085 instead of BC490B).

    What I can say is that the measures are the same, but what I hear is completely different!

    One amplifier sounds if it was raining cats and dogs, the other sounds as if it was full sunshine."


    That I can relate to. I think I see your point. If you told me your amp had a DF of 200 and THD of 0.001% I would probably just say "neato". When you say something like what is quoted above, then it piques my interest.

    "That is why, numbers are just numbers …. And none of them can explain why this amplifiers sounds so good or so bad!"

    Well..... I don't know what to say about this. People just like numbers..... It's probably best not to show them any numbers at all and just let their ears decide. What a concept.

    So, now, what is the output impedance of your amp?

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    Re: Re: Amplifiers are more significant than you may think!

    [QUOTE]Originally posted by Giskard

    That I can relate to. I think I see your point. If you told me your amp had a DF of 200 and THD of 0.001% I would probably just say "neato". When you say something like what is quoted above, then it piques my interest.

    Please read the numbers, those are not from me but from several magazines who printed several test benches.

    Frequency Response at 10 Watts: 15 Hz-60 000 Hz
    SNR unweighted/weighted (BC490B): 98 dB/103 dB
    Gain to 1 kHz - 8 ohms rated output: 31dB
    Input impedance bal./unbal: 39/30/18 k-ohms
    CMRR 40Hz/ 1 kHz/ 10 kHz (INA134): 84 dB/84 dB/78 dB
    Rise Time: < 6 µs
    Output impedance: 0,059 ohm
    Damping factor 8ohms; 136
    Distortion 1000 Hz/8ohms: 0,009%
    IM distortion (SMPTE) at clip: 0,026%


    What else can I say?

    I can point a thread with full test reports but I want your agreement as a moderator (not other to think that this is just raw advertisement for what I am doing)!

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    For those interested in (I do not want this post to be considered as advertising and if it is I agree this message can be removed by our favourite moderator) we have just launched our own forums about PSS amplifiers!

    http://www.pssaudio.com/forums

    You are welcome and hope this will contribute to improve what we try doing the best; amplifiers sounding good!

    And our website:

    http://www.pssaudio.com

  9. #9
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    audio gear and parts

    YES! I have been saying this for years. You CAN hear tonality differences between different brands of pots and TYPES of pots!

    You can also hear differences between different brands and types of resistors and capacitors!

    Yes, the NUMBERS do not tell you how an amplifier sounds! If the numbers were really any indication of how an amp sounds then McIntosh amps would sound terrible with their ratings of 0.25% THD distortion and incredibly high damping factor of 18 on my Mc2105! Quite the contrary thesae amps sound wonderful, and everybody loves vintage Mc,s!

    Conversely, TOO HIGH a damping factor can actually interfere with your sound, particularly horn loaded systems! If its too high it can get stiff and sterile sounding!

    Numbers do sell amps and other audio gear, but the best way to shop is by ear!

  10. #10
    Senior Member Steve Schell's Avatar
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    Damping factor

    Scott, I agree cmpletely on the issue of damping factor. We are in good company; I ran across this paragraph the other day. It is from J.B. Lansing and J. K. Hilliard's 1945 article, "Improved Loudspeaker System for Theaters":

    "Sufficient damping of the vibrating elements of the units are provided in the magnetic circuit so that it is not necessary to provide additional damping from the driving amplifiers. In the past it has been customary to adjust the amplifier output impedance to a value of approximately one-half to one-third of the average loudspeaker impedance. Improved performance can be obtained with the new loudspeaker when the amplifier and loudspeaker impedances are approximately equal."

    This article was written to introduce the new Voice of the Theatre systems; the speaker units they were referring to were the 288 compression driver and 515 woofer. The input impedance of the N-500C network described in the article was 12 ohms. Sooooo, it looks like we need to fire up our relatively high output impedance tube amps when running our vintage Altec systems, if we want to be in keeping with the designers' intentions.

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    You could do that!

    Or you can use a vintage McIntosh with its NO damping, and hear very nice sound! I like Mc,s on horns and tweeters personally!

    Then of course theres Crown! Some of the amps they make now? Macro Reference with a damping factor of 20,000 to 1. Is this really neccesary to achieve good sound?

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    Damping factor...

    Hey, guys...

    Interesting dialogue - prompted me to review the roads we travelled on this a while back. Here's some Links:

    http://www.audioheritage.org/vbullet...damping+factor

    http://www.audioheritage.org/vbullet...r&pagenumber=1

    Yea, I know the threads here get a bit frayed, but the cloth woven is oh so interesting.

    I'm personally using QSC's in bi-amp for both highs and lows, and cannot imagine anything finer. They simply control those 2245H's with uncanny precision and depth. But maybe the highs should get special treatment...

    I feel an eBay urge coming on

    Comments?
    bo

    "Indeed, not!!"

  13. #13
    RIP 2010 scott fitlin's Avatar
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    QSC

    QSC rates their amps damping factor >200. Compared to some of Crowns amps this isnt exorbitantly high. Its definitely good enough!

    I find that amps that have extremely high damping factors dont really sound that great with horn loaded bass!

    BGW isnt as high as Crown and yet they make what I consider to be tight, taut low end.

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    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Thanks, Scott.

    The two QSC's I run (CX302 and CX502, top and bottom, respectively) are rated at >500 damping factor. This seems smart when aggregating the impedance of the speaker leads and the transducers into the overall impedance of the circuit - certainly for the LF.

    So, give me the perspective on how/why this is not optimized for horn-loaded situations? Maybe tube amps are "sweeter/smoother" for the high-end?
    bo

    "Indeed, not!!"

  15. #15
    RIP 2010 scott fitlin's Avatar
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    well

    If the amp has an extremely high damping factor it will have a really tight grip on the woofers movement! Now, control is one thing, but if its to tight horns dont sound natural! The bass tends to get hard sounding! I have also read that if damping is too high it can cause smearing!

    For some reason, the amps i tend to favor for running my bass horns never seen to be the ones with an extremely high damping factor!

    These days I seem to be liking BGW on sub bass and Bryston on 15,s! Both brands rate their amps as >500. Unlike some other amps that are 1000 and higher! I kind of feel, that while they can design an amp to meet certain numerical figures, maybe, just maybe, there is a point at which the amp starts to lose its musicality!
    Last edited by scott fitlin; 08-20-2003 at 08:00 PM.

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