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Thread: Stereophile | January 2017 Issue

  1. #401
    VIP/Donor [VIP/Donor] microstrip's Avatar
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    Quote Originally Posted by f1eng View Post
    Just agreeing with those 1999 observations.
    Still do. Nobody has yet produced a cogent reason why people buy these items other than this.

    For me it is no problem to buy what you like to listen to best, that makes sense.
    If you want to justify it to yourself any way you like, fine.
    Unfortunately we are only debating with the static old fashioned measurements that many high-end designers consider insufficient to characterize amplifier subjective sound quality. Measurement technology evolved a lot - modern analyzers supply lots of information on dynamic and transient behavior, but we do not have information on recent developments and go on using the same old arguments, often discussed in other audio forums, including the DIY community that spends a large time on the subject. THD is insufficient, spectral analysis is a little better, but IMHO still insufficient to explain what we hear.

    BTW, I was just checking the spectra of distortion of one amplifier I am selling to a good friend - comparing the performance of both channels is a great and reliable way of checking its condition. Besides, some tube amplifiers have an internal potentiometer that can be adjusted to minimize second harmonic - spectral analysis is really a great tool.
    Last edited by microstrip; 01-11-2017 at 01:04 PM.
    Under construction around a pair of Wilson XLF's and a DCS Vivaldi 2.0 stack : cj GAT, Lamm M1.2R, TA OPUS MM2 +TA XL digital, TA XL gen V power cables ...

  2. #402
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    Quote Originally Posted by Aries Cerat View Post
    So you have the Animas?Very nice. We got best of show with the excellent Animas in Munich's 2011 show paired with our full electronic set up.With our Exsequor amps.SE though:-)
    I remember that!
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    Quote Originally Posted by microstrip View Post
    As most solid state amplifiers Gryphon's have plenty of feedback - they only claim zero global negative feedback.
    We should not be afraid that it sounds different from SET's!
    interesting and good to know. have no fear....I like what i hear with Gryphon...and have never had any desire to look elsewhere. That said, i admit i have not spent sufficient time with SETs (Lamm, Kondo) to really get to know them, and certainly have never compared in our system. i have heard Kondo in another system, and found that system enthralling. One interesting observation is that a number of the reviews i have read about Gryphon each seem to liken Gryphon's tonal purity specifically to that of SETs, while obviously have the sheer power to create endless reserves of dynamic range and bass slam.
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    So after watching the most welcome tennis match of ideas, science, calcs, i make the following observations:

    1. All amps have some level of distortion...whose pattern and type various by design and implementation. measurements of every order, how much matters and does not matter or is inaudible: all is not a fully understood science to the nth degree...more work to be done
    2. The human ear is not a machine and seems to have its own 'in take/processing science' which must be taken into account when designing an amp which is always going to have some level of distortion.
    3. Amp design goals are to minimize distortion...but probably ALSO to minimize that distortion in a way that complements the human ear/hearing/perception mechanics
    4. The concept of 'euphoric' distortion is probably a personal taste thing even if there are generalizations one might attempt to take. So care must be taken in HOW human ear/hearing/perception mechanics are incorporated into any design. Ideally, you focus not on simple human preferences but more on actual human physiological ability to hear/discern certain kinds of distortions
    5. Adding in the overall system to amp design/choices, its clearly important to focus incredibly hard on the amp-speaker combination. An amp that is loafing along, easily able to perform at its best with lowest distortion when connected to a particular speaker is clearly a good place to start...and in an ideal world perhaps the amp has been specifically designed to drive the exact load characteristics shown by the actual speaker. (Here come the Active Speaker proponents!)

    Basic Question: Is it easier to design a low distortion 10-watt amp than a 200-watt amp? Is it easier to design a low-distortion 100db efficient speaker than an 85-db speaker? This may be a ridiculous question, in which case I withdraw the question, your honor.

    Otherwise, carrying on: if the speaker answer is "equally easy/difficult to design the efficiency", but the amp answer is "easier to design low distortion low-watt amp"...should that lead us to search our favorite of high efficiency speaker...and go for amps (whether higher powered or lower powered)...that are as low distortion as possible at 1-10 watts?
    Speaker Wilson X-1/SLAMMS / Velodyne DD18+
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  5. #405
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    Quote Originally Posted by LL21 View Post
    1. All amps have some level of distortion...whose pattern and type various by design and implementation. measurements of every order, how much matters and does not matter or is inaudible: all is not a fully understood science to the nth degree...more work to be done
    What I've noticed is missing on this thread is the type of distortion. THD isn't the audible distortion present when listening to music - it only shows up on sinewave testing. The distortion which its possible to hear on music (when your system is sufficiently sub-standard) is intermodulation distortion. This is a large reason why THD measurements aren't telling us very much about amplifier sound. This important detail has been understood since the work of Brockbank and Waas many decades ago - they showed that IMD products would completely submerge THD harmonics when the stimulus is normal music.

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    Quote Originally Posted by opus112 View Post
    What I've noticed is missing on this thread is the type of distortion. THD isn't the audible distortion present when listening to music - it only shows up on sinewave testing. The distortion which its possible to hear on music (when your system is sufficiently sub-standard) is intermodulation distortion. This is a large reason why THD measurements aren't telling us very much about amplifier sound. This important detail has been understood since the work of Brockbank and Waas many decades ago - they showed that IMD products would completely submerge THD harmonics when the stimulus is normal music.
    Actually the one thing that was really NOT being discussed on this thread was THD. Geddes showed in a couple of paperd that there is NO correlation between THD and sound quality. He also showed no correlation between IMD and sound quality.

    The harmonics generated, either pure or through intermodulation, will determine audibility and obnoxiousness of the distortion. Correct weighting is necessary for a good correlation with perception.

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    Quote Originally Posted by morricab View Post
    Geddes showed in a couple of paperd that there is NO correlation between THD and sound quality. He also showed no correlation between IMD and sound quality.
    Got a link to this claim on IMD? I am familiar with some of Geddes' work and even entered into an attempt at questioning him about it on DIYA but he turned out to be fairly defensive. The paper he referred me to examined and modelled only static distortions which in my view renders part of it irrelevant.

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    Is it easier to design a low-distortion 100db efficient speaker than an 85-db speaker?
    Hello LL21


    I think because of the higher sensitivity the higher efficiency speaker will tend to be more linear and operating in that range more often than not. As I see it the higher efficiency has benefits all the way down the line as all components will be operating in essentially a low power mode at listening levels we would typically listen at. This is even more important if we listen at anything near life like levels as the 85db speaker is decidedly on the wrong side of the power curve and both the amplifier and individual drivers will be working quite hard at that point. Lets face it a 15db advantage is huge as far as the power levels required for 110dB peaks. Even at an average of 95db you are looking at 10 watts vs milliwatts That's at 1 meter and does not account for distance to the speakers. Distortion levels in higher efficiency drivers can be quite good so an advantage all around.

    Attached is a distortion measurement on JBL KS9900 speaker system at 96db you can see that the distortion is under .3% in the midband and quite good over the entire bandwidth.

    Rob
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    Last edited by Robh3606; 01-12-2017 at 09:00 AM.
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    Quote Originally Posted by opus112 View Post
    Got a link to this claim on IMD? I am familiar with some of Geddes' work and even entered into an attempt at questioning him about it on DIYA but he turned out to be fairly defensive. The paper he referred me to examined and modelled only static distortions which in my view renders part of it irrelevant.
    Both papers can be found on Geddes website

  10. #410
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    Quote Originally Posted by f1eng View Post
    SET amps produce lots of distortion
    That statement itself is misguided.

    Quote Originally Posted by f1eng View Post
    but usually sound nice therefore the distortion they are producing is euphonic.
    That is incorrect too: the distortion doesn't make things better: the 2nd order distortion doesn't sound as horrible as 3rd order.

    There are some nuances there that appear to elude you.

    Quote Originally Posted by f1eng View Post
    The idea that there is some magic about SETs which makes them sound nice despite being non linear has made a renaissance, I don't buy it and I have never seen a convincing hypothesis as to why such magic could exist.
    Simplicity of circuit is one, the restitution of transients is amazing.

    Quote Originally Posted by f1eng View Post
    I am still convinced that people like SETs because of their distortion characteristic is changing the sound to their taste. I see nothing wrong with making such a choice btw.
    Flawed reasoning => Flawed deductions.
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