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Setting-up our home systems - do we have the basics in place?

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  • Setting-up our home systems - do we have the basics in place?

    I've been reading on HUG recently of the valiant efforts folk have made to bring together audio electronics from various makers and of various technologies. Examples like new DACs hanging off the back of CD transports, or streaming audio boxes, and in my case, the purchase of a high quality Astell & Kern portable audio player (bought for next week's KJ M40.2 UK demo).

    We have talked extensively about the fact that the home audio system is an unstructured electrical signal chain, unlike the studio environment where inter-equipment signal levels are expected to conform to a rigid voltage standard. We've also demonstrated how easy and inevitable clipping and signal compression is when the user assumes - wrongly in most instances - that the output voltage (representing music) from equipment X can be connected to the input of equipment Y and the full, uncorrupted musical dynamics passed from X to Y.

    So I have in my hand the Astell & Kern Junior, here. [Oddly, their website does not steer to individual product pages. You need to manually go to Portable then to AK JR to find this item]. The technical specs are extremely impressive indeed, far, far, far beyond the resolution capabilities of even the finest, freshest 18 year old ears, clean or not. Or even the best microphones money can buy.

    AKJR.jpg

    So, I have this player, the spec look impressive. So what? How do I know they are not the work of an imaginative marketing department? How do I know that this specimen off the production line that I have on my desk here - rather than an idealised, theoretical, hand built, selected specimen meets or even approaches the specification above? How do I know if the design has been changed and that spec is based on a money-no-object prototype that never saw the light of a production line?

    And more than any of that, how do I know that when I arrive and hook this up to an audiophile amplifier* I have probably never seen nor heard of at the KJ store on 24th October, that I can be confident that I will be demonstrating the M40.2s to their best? How do I know that the output voltage from the A&K Junior - or indeed a CD player that KJ may have on hand as a backup, or a DAC or any other piece of fancy audio electronics, is going to be operating in its linear region to be 100% sure that what you hear of the M40.2 is wholly free of any corruption from the driving electronics?

    Naturally, the steps that I take in advance of the KJ demo are precisely the same as those that you should take when presented with equipment choices at home, or ideally in the dealer's premises. What we need is a simple, foolproof, non-technical and fast method of confirming that equipment Y's input is comfortable with the output voltage of preceding equipment X being 'stuffed-up' its input terminals.

    Were we in a sound studio, we could have high confidence that whatever equipment the producer asked us to plug-together to achieve the sound he visualised - compressors, EQs, parametrics, limiters, sweeteners, sonic exciters and the rest - that we could do so with little doubt that they are all electrically compatible in whichever input/output sequence we wished.

    So, if for convenience due to limited cable lengths we plugged an EQ box into a sonic exciters then that into a compressor or alternatively, first the compressor then the sweetener then the limiter, we could do so with little concern of mismatch, clipping, overload or distortion. Unfortunately, in the lawless, unregulated, non-standardised home audio environment, there is no I/O voltage standard to adhere to, and whichever item along the chain corrupts the signal as it passes irrecoverably destroys fidelity for the remainder of the chain.

    *I have not asked for nor specified the CD player, DAC, amplification or cables that will be provided by KJ for the demo, except that the amp must be adequately powerful and solid state. Beyond that, I am not concerned.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  • #2
    Pre-flight checks for the KJ demo

    Originally posted by A.S. View Post
    ...And more than any of that, how do I know that when I arrive and hook this up to an audiophile amplifier* I have probably never seen nor heard of at the KJ store on 24th October, that I can be confident that I will be demonstrating the M40.2s to their best? How do I know that the output voltage from the A&K Junior - or indeed a CD player that KJ may have on hand as a backup, or a DAC or any other piece of fancy audio electronics, is going to be operating in its linear region to be 100% sure that what you hear of the M40.2 is wholly free of any corruption from the driving electronics?

    Naturally, the steps that I take in advance of the KJ demo are precisely the same as those that you should take when presented with equipment choices at home, or ideally in the dealer's premises. What we need is a simple, foolproof, non-technical and fast method of confirming that equipment Y's input is comfortable with the output voltage of preceding equipment X being 'stuffed-up' its input terminals.

    Were we in a sound studio, we could have high confidence that whatever equipment the producer asked us to plug-together to achieve the sound he visualised - compressors, EQs, parametrics, limiters, sweeteners, sonic exciters and the rest - that we could do so with little doubt that they are all electrically compatible in whichever input/output sequence we wished.

    So, if for convenience due to limited cable lengths we plugged an EQ box into a sonic exciters then that into a compressor or alternatively, first the compressor then the sweetener then the limiter, we could do so with little concern of mismatch, clipping, overload or distortion. Unfortunately, in the lawless, unregulated, non-standardised home audio environment, there is no I/O voltage standard to adhere to, and whichever item along the chain corrupts the signal as it passes irrecoverably destroys fidelity for the remainder of the chain.

    *I have not asked for nor specified the CD player, DAC, amplification or cables that will be provided by KJ for the demo, except that the amp must be adequately powerful and solid state. Beyond that, I am not concerned.
    Firstly, thank you for your nearly 5000th post. A milestone indeed!

    As you do not know what amplifier awaits you at KJ, the only preparations I can imagine involve sourcing a high quality multimeter or oscilloscope to take with you, to check the amp's inputs for clipping.

    I very much hope that I am completely wrong! However if you do not know the input sensitivity of the amp, and it does not have adjustable gain with a indicator light or levels meter, I don't know how you can avoid clipping otherwise.

    Comment


    • #3
      Maybe.... not.

      Originally posted by Dougal View Post
      Firstly, thank you for your nearly 5000th post. A milestone indeed!

      As you do not know what amplifier awaits you at KJ, the only preparations I can imagine involve sourcing a high quality multimeter or oscilloscope to take with you, to check the amp's inputs for clipping.

      I very much hope that I am completely wrong! However if you do not know the input sensitivity of the amp, and it does not have adjustable gain with a indicator light or levels meter, I don't know how you can avoid clipping otherwise.
      Pleasure. The object is to leave behind something lasting.

      You're line of thought is very much in agreement with mine. Arriving early, no matter how early, there is a likelihood (I've been told the number of visitors that have pre-booked already, and it's very flattering) that one or two will have beaten me to it. In which case, messing around with a oscilloscope or multimeter or indeed any test equipment as a sort of performing monkey in the public gaze fills me with dread.

      So, as you hint, we have to find another simpler way which will draw our focus to 80% of any latent issues for only 20% of the effort. What can we do in the relatively subdued lighting of an audio demo room, having forgotten our spectacles in the rush to catch the train, with some attendees already gathered, with no test equipment (too heavy to carry by train even if the ultimate solution) and with just ten minutes until the official opening?

      Thoughts? What can we fall back on and have some confidence in?
      Alan A. Shaw
      Designer, owner
      Harbeth Audio UK

      Comment


      • #4
        Suggestion -1

        I would bring a recording of a revealing test signal at different levels. A good set of experienced ears should be able to decide if the higher levels of the signal drive the amplifier into clipping.

        If that happens, and if your player has an adjustable output level, you can see how much you have to lower the volume to get rid of the clipping. If the player does not have an adjustable output you are out of luck, unless you bring your own passive volume control. I notice that the A&K player's output level is marginally below the notional 2.0V CD standard.

        Comment


        • #5
          Response - 1

          Originally posted by willem View Post
          I would bring a recording of a revealing test signal at different levels. A good set of experienced ears should be able to decide if the higher levels of the signal drive the amplifier into clipping.
          That looks like a very fine solution to me. Using our own ears. We are 'audiophiles' aren't we? If we are, are we afraid to use our special talents to detect a little audio distortion? If we can't do that, is there any hope?

          So, we arrive at the demo with absolutely no test equipment at all. With perhaps one exception. We bring with us some sort of, as you say, "revealing test signal [recorded] at different levels".

          Any suggestions as to what might make a simple but effective "revealing test signal [recorded] at different levels" which even the least technically able listener could use to extract some useful information about the performance of the audio electronics?

          {This is A.S's 5000th post}
          Alan A. Shaw
          Designer, owner
          Harbeth Audio UK

          Comment


          • #6
            Off topic?

            Gentlemen: I appreciate the hardware suggestions, but this is not what this thread is concerned with. I have said that I am unconcerned by what electronics I find upon arrival. Any brand will do, but for power and load-independence, I'd really expect a solid state unit. If much more time to test is available alongside test equipment, tube amps could be cautiously explored. Tube amps will have, to one extent or another, load-dependent performance with any real-world loudspeaker loads which will, as we know, influence the amp's frequency response, and hence perceived sonics.

            The clue is in the title - have or how do we resolve the basics about signal level compatibility between source and amplifier?

            So, again: thoughts about how we can proceed to resolve that fundamental issue regardless of whatever amp is placed in front of us? If we don't get this matter under control, we will potentially fall short of the performance potential of the speakers and the presentation will be a waste of time for attendees, let alone me.
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • #7
              Sensing the difference in relative levels

              Suppose you create/record, at a gradually increasing level, a series of pairs of test tones (at the same single arbitrary frequency) whose relative levels differ by some small - yet readily detectable - value, perhaps, 1dB.

              For example, the first pair of tones could have levels of 0.1V and 0.11V (+1dB higher). The next pair of tones might have levels of 0.25V and 0.28V, and so on. Eventually you would reach levels on the order of 2.0V and 2.25V; and higher, if necessary.

              You would then play these test tones through the equipment under evaluation until the point at which the difference in levels between the pairs of tones can no longer be discerned - indicating that the onset of non-linearity has been reached.

              Comment


              • #8
                Another Suggestion - attenuators

                If you have no test equipment, no recordings of tones on the AK player, and no control over its output (from the player itself), the only possible solution I can think of would be to bring a pair of attenuators. Surely that's not too much to ask - they will fit in an inside pocket.

                Once the player is connected you can then check how far the volume control on the pre-amp or integrated (whichever it is) can be raised. If the volume is too loud before it gets halfway, plug in the attenuators.

                Your next obstacle surely must be room acoustics. I know KJ have a good demo room but I think you are (sensibly) presenting this problem as if the demo room was an unknown quantity. Once the voltage issue is accounted for, that might be a useful direction in which to steer the discussion!

                Comment


                • #9
                  The test material - 1

                  OK, let's take a step back.

                  Assume then, that I arrive at KJ with my little media player and/or with a home made CD disc, and on it are two "test tracks"* that I have prepared. They are these:

                  Loading the player ...
                  TT1

                  Loading the player ...
                  TT2

                  Now - and this is a trick question! - putting yourself in the position of either a) me, preparing fro a public demo which could have significant financial consequences for the store and for Harbeth b) yourself as a prospective purchaser of quality audio equipment concerned about equipment matching, could we learn anything useful about the system performance from playing and critically listening to either of the above randomly selected music tracks? Or any other two randomly selected music tracks? Or your favourite music tracks? Or your partners?

                  The key word here is 'music'. Consider this post after eliminating the word 'music'.



                  *In very big quotes indeed.
                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

                  Comment


                  • #10
                    Test tracks

                    What I meant was test tracks with sine waves at e.g. 0db, -3 db , - 6db etc. Are they clean when played even at 0 db, or do you have to go down one or two levels? If you have to go down, then turn down the volume on the little player, and try again: is the 0 db clean now, or still not yet?

                    Comment


                    • #11
                      Not clipped?

                      Wouldn't it be important that it's the music itself that is not clipped as well and that any test music played for a public demonstration should be one that has been mastered well with peaks still having sufficient headroom?

                      Comment


                      • #12
                        Yes, and caution!

                        Originally posted by tmokbel View Post
                        Wouldn't it be important that it's the music itself that is not clipped as well and that any test music played for a public demonstration should be one that has been mastered well with peaks still having sufficient headroom?
                        Good answer.

                        Would it surprise you then if I told you that the pop track (TT1) is unclipped, but the piano piece (TT2) I have deliberately clipped quite aggressively? And neither you nor I as casual listeners can hear that quite serious clipping. Right?

                        There is a learning lesson here which considering the vast amount to energy poured into the amplifier debate here should be taken serious note of: (a) 'clipping' is a technical term to describe audio that has (or would have were it not clipped) voltage peaks that the system element (amp, CD etc.) handling that audio is incapable of passing through unmolested.

                        Or in simple language: (b) 'clipping' is what happens when the dynamic range of the audio is constrained by the circuitry through which the audio voltage signal passes, intentionally or not.

                        Or another more florid way: (c) 'clipping' is when the tops and/or bottoms of the voltage waveform representing the music are irreplaceably damaged by being chopped-off.

                        Note - in the case of (a), (b) and (c) we are defining clipping as a technical issue, one which can be easily exposed by the use of suitable test equipment monitoring the voltage waveform that is the music - an oscilloscope for example. We may or may not be able to actually hear clipping until its presence exceeds a certain threshold of audio nastiness, which may well vary from music to music, equipment to equipment, listener to listener and so on.

                        We know that clipping is very often present in the home audio system because there are no technical standards for equipment audio inputs/outputs, no inter-manufacturers equipment technical standards to meet (DIN standard is long forgotten), no industry governing body to set standards, no consumer body to oversee standards, no legal imperative to hold manufacturers to a technical commonality and absolutely no motivation whatsoever for manufacturers to operate on a level playing field when we know that audio equipment equipment 'sonic signatures' are directly related to loudness. It's a completely lawless environment of deliberate consumer confusion, and very good for business. It's the perfect commercial environment.

                        So, back to the point. We arrive at the demo site and we've never seen the audio electronics replay equipment before in our lives. We've read nothing about it, we've foolishly left our spectacles behind and now, long sighted as we are, couldn't read the manufacturer's tiny-font technical documents even if we wished to. We did not hand carry any technical gear with us. We have to relay 100% on our ears, good, bad, young, old, clean or not and we have to explore the system's technical synergy (the compatibility of equipment passing the audio system along the chain from source to speakers) using only those ears.

                        Do we agree that for the initial basic test of our system linearity (i.e. freedom from inter-equipment level mismatching), what we must do before we play the first music track, is apply some sort of sonic test signal?

                        Agree or not?

                        And what would be the standard way of getting a quick sense of any latent system issues requiring perhaps no more than 60 seconds of probing - and just our ears? Can we also agree that using music as a primary test source for the initial evaluation - our 60 second test -would be a very bad decision indeed? This is fundamentally important point.
                        Alan A. Shaw
                        Designer, owner
                        Harbeth Audio UK

                        Comment


                        • #13
                          Get it

                          Originally posted by A.S. View Post
                          We know that clipping is very often present in the home audio system because there are no technical standards for equipment audio inputs/outputs, no inter-manufacturers equipment technical standards to meet (DIN standard is long forgotten), no industry governing body to set standards, no consumer body to oversee standards, no legal imperative to hold manufacturers to a technical commonality and absolutely no motivation whatsoever for manufacturers to operate on a level playing field when we know that audio equipment equipment 'sonic signatures' are directly related to loudness. It's a completely lawless environment of deliberate consumer confusion, and very good for business. It's the perfect commercial environment.
                          Never realised this, is it really that bad ? Now I understand your problem (I think), so this could occur everywhere; dac, cd, amplifier, cables.

                          Btw, the clipping of the second track (TT2) was was only clear when I played the track on my stereo.

                          Comment


                          • #14
                            Dynamic range compression

                            Originally posted by martin1305 View Post
                            Never realised this, is it really that bad ? Now I understand your problem (I think), so this could occur everywhere; dac, cd, amplifier, cables.

                            Btw, the clipping of the second track (TT2) was was only clear when I played the track on my stereo.
                            Yes the piano track is significantly clipped. If I were a recording studio engineer and my CD master had gone to the pressing plant clipped like that, I would by now be out of a job. Dismissed for incompetence.

                            As I said:

                            Note - in the case of (a), (b) and (c) we are defining clipping as a technical issue, one which can be easily exposed by the use of suitable test equipment monitoring the voltage waveform that is the music - an oscilloscope for example. We may or may not be able to actually hear clipping until its presence exceeds a certain threshold of audio nastiness, which may well vary from music to music, equipment to equipment, listener to listener and so on.
                            So, to use an old cliché from audio magazines of the 1950s - 'open the window and more dirt comes in' - you've heard that as you improve the standard of the replay system you start to hear issues that are not brought to your attention on a cheap muzak system. There may well be issues in the source recording, but they are buried under many other confounding issues in the home audio system so that they just are not audible until a certain standard of overall synergy is reached. And that 'assurance threshold' has no automatic correlation with cash, and a total correlation with inter-equipment voltage matching.

                            My issue, as you surmise, is that I want to be as sure as I can that the replay system will be completely blameless come the demo. Or indeed, during development of a speaker, or at any other time. And so should you verify your own home sytem. You have to absolutely validate that the resolution potential I've worked hard to build into our speakers is available to you and that some element along the electronics chain in your listening system has not limited the performance. And clipping - dynamic range compression - is the most obvious one since we can usually assume that hiss, distortion and frequency response are all as good as they need to be with modern systems.

                            And dynamic range compression (clipping) during playback is the consequence of either inter-equipment audio signal voltage mismatching and/or inadequate amp power to drive the speakers. So we need plenty of amp power watts and simultaneously we need to investigate the audio signal level-matching issues from the music source onwards.

                            So - what test material can we use? If we are going to prepare a test CD and also upload a test track onto the A&K media player (we could use the same test track - right?) what would that "look like, smell like and sound like"?
                            Alan A. Shaw
                            Designer, owner
                            Harbeth Audio UK

                            Comment


                            • #15
                              The basic basics.

                              Originally posted by elviejo
                              Whose ears are better at discerning the appropriate sound of Harbeth 40.2's than Alan Shaw's?? Yes the ear is a very imperfect...
                              Forget the M40.2s. This system validation has absolutely nothing whatever to do the fact that the speakers are Harbeths, or M40.2, or big speakers or small speakers, or new speakers or old speakers, or speakers with ripped cones or tatty cabinets or indeed my ears. The speakers are, for the purpose of this discussion, a complete irrelevance. In fact, we could easily perform this initial 60 second 'system check' as a group activity before music at the demo - it's not a secret and I can guarantee you that everyone in the room, even the least technically able or interested teenager, could hear for him/herself what the limitations of the system are. Nothing to do with the speakers - all to do with the electronics.

                              We are trying to validate that the signal that passing out of the source - be it CD, streamer, media player, vinyl or whatever - is passed 100% cleanly through whatever equipment exists between the source and the speakers. That usually means, in a minimalist audiophile system, through just the amplifier.

                              The contributions have been most useful and thanks for all of them. The picture that an objective reader with a little technical knowledge would see is that - and I do not mean this as a criticism, just an observation - that it has suited the audio industry via the media to breed a generation of consumers who have no basic understanding of the technical side of audio at all. This is really disturbing. It's disturbing because if the basic high school knowledge of audio voltage is absent from the audiophile's lexicon of understanding, his house is built on sand. If there is no appreciation of audio as encoded onto a voltage, it follows that there will be no understanding of audio as a sound wave and audio as a perceived sound level, a loudness. And without that appreciation, identical sister products off the same production line can be manipulated in a demonstration environment so that the louder one takes on a distinct personality when in fact, they are identical in every way. I'm frustrated because after the 5000 posts that I've personally contributed here, this basic testing strategy should not need exploring. I've failed miserably in transferring knowledge and I just do not know where to turn now to fill the gaps.

                              As was stated above

                              Originally posted by martin1305
                              When I auditioned a few weeks ago different amplifiers I had no idea about these different standards which could result in clipping, distortion etc. It could be the explanation why the amplifiers all sound different or maybe it must say more or less clipped/distorted/.
                              I'm reluctant to go off at a tangent, but I'd like to take you over the very point that we've been championing for years, namely the danger of allowing loudness differences to creep into so-called comparisons of A v. B. Let's ignore for a moment long delays in turning-off A, swapping over cables to B and powering-up B, a process which could take many minutes, and of the impossibility of the human brain accurately recalling sound events minutes apart: let's just look at how clever we are at detecting level differences.

                              steps.jpg

                              We can link to an on-line sound-level detection app. Select 6dB level steps, and play the app at a normal listening level. You should be able to detect an unmistakeable difference in loudness between the initial sound and the +6dB or -6dB. Then select 3dB steps, test yourself again, and so on. When you get to the 0.5dB selector, take special note of how you react and then on to 0.2dB.

                              The link is here.

                              We can return to this again, but for now let's just try and build some foundations so that we can get some useful insight into how the system (probably in a minimalist system, the amp) will behave with our source connected.
                              Alan A. Shaw
                              Designer, owner
                              Harbeth Audio UK

                              Comment

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