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  • Should we stack our equipment

    I write this based on personnel experience of this method we use to organize our equipment.
    Tube devices seem to be especially sensitive products.
    I built a simple vertical rack to house my stuff.
    On top about 8 feet above the floor was a ps audio p10
    about 3 feet (36) inches below was my Lampi dac
    the toroidal transformer is a donut shaped transformer made so it radiates little through the middle. Typically sitting flat with the hole in the middle.
    We cannot effectively shield mAgnetic radiation , but we can redirect it's pattern.
    Well ps audio seems to try this with a metal plate on top and bottom.
    Well at 3 feet below this transformer sat my tube dac.
    It made my tubes hum. I had to use a tin or better yet a copper made cage. The cage was then grounded to the dac.
    Applying my hands over the tubes greatly lowered this hum.
    I even tried a copper paper on shelves all grounded.
    Nothing made it zero.
    Now if I took this dac and moved it off the shelf in front of the rack all was zero or close too.
    So this made me wonder why do we stack , does this common method effect the sound.
    The short answer is yes. Some very well made products take the psu out of the device completely
    my ML NO 26 does this and remarks to keep 2 feet away from the left side if it has the phono option.
    What do others do here and any stories you may have to share.
    Lastly I tried many grounding methods as well to stop the hum.
    speakers cust infinity IRS V , new caps and LPS , magnets etc.
    mark levivson pre no 26 amps no 33
    digital three cust servers , win ser 2016 , AO
    Dacs lampi various

  • #2
    I've always prefered the clean box-dirty box approach so all of my components have separate power supplies. When ever possible I stack the power supplies in their own rack each with their own shelf and separated by as much distance as possible. The greater the separation/distance/mechanical isolation the better. Always results in lower noise floor with more realistic playback.

    Comment


    • #3
      Always a good tech answer joe. I'll bet your setup rocks
      speakers cust infinity IRS V , new caps and LPS , magnets etc.
      mark levivson pre no 26 amps no 33
      digital three cust servers , win ser 2016 , AO
      Dacs lampi various

      Comment


      • #4
        Originally posted by Alrainbow View Post
        We cannot effectively shield mAgnetic radiation , but we can redirect it's pattern.
        Redirecting a field and shielding are the same thing, just different conceptual terminology. Mu-metal tube shields redirect magnetic fields. Steel does to, just not as effectively.

        Originally posted by Alrainbow View Post
        I had to use a tin or better yet a copper made cage. The cage was then grounded to the dac.
        Applying my hands over the tubes greatly lowered this hum.
        If copper or your hands changed the hum then it was not the result of a magnetic field in the first place. Copper is non-magnetic. I assume most hands are too. The fact that hands and copper changed the hum indicates the hum field was electric or electromagnetic. Electric and electromagnetic fields are redirected by conductive materials, magnetic fields are redirected by magnetic materials.

        Originally posted by Alrainbow View Post
        Now if I took this dac and moved it off the shelf in front of the rack all was zero or close too.
        I assume turning the DAC off or disconnecting its power also reduced the hum to zero?
        Originally posted by Alrainbow View Post
        So this made me wonder why do we stack , does this common method effect the sound.
        The short answer is yes. Some very well made products take the psu out of the device completely
        my ML NO 26 does this and remarks to keep 2 feet away from the left side if it has the phono option.
        The long answer is that there is always an AC magnetic hum field around power transformers, and keeping that out of the audio circuits is tricky and expensive, but not impossible. Magnetic shielding (mu-metal) is difficult to work with and costly, but even without it there are so many devices with built in PSUs that have no significant hum issues, including thousands of pro audio products. Separate PSUs that can be separated by distance is sort of the easy way out. Kind of surprising the ML resorted to that, but I also don't see anything about it having to be 2 feet away. The manual suggest the PSU can be directly adjacent to the Pre on the right side. The only other reference to spacing relates to heat dissipation.

        As to stacking equipment...it's to be assumed that at some point if a piece of kit is rectangular and doesn't have glass bottles protruding, it will at some point be stacked with something else. For a designed not to acknowledge that is naive at best. If equipment is designed so that it either radiates a strong hum field, or is highly susceptible to a hum field, then IMHO they have serious design flaws. And if a device is so sensitive to stray hum fields that it can't tolerate a stacked installation, then that should be clearly noted in the literature or on the device.

        There might be some magnetic hum field radiated from a PSU, but there should be practically zero electric or electromagnetic radiation outside of the device.

        Again, referring to pro audio, nearly all pro audio gear is designed to be rack mounted with rarely more than 1 RU between them, and often no space between them. That kind of gear rarely has inter-device hum field issues. I only say "rarely" because while I've never had that issue, perhaps somewhere on the planet someone has. For example, Dolby 361 noise reduction units are 1ru, internal power transformer and PSU, and have input and output audio transformers. They can be stacked directly with no space, and no hum (they are, after all, noise "reduction" devices).

        Only with the advent of mass produced low cost analog or high efficiency modular switching power supplies has pro gear had external PSU designs. And that's because the PSU is made by a third party, and meant to be stand-alone, often with integral plug (wall-wart design). Switching PSUs also can radiate an EM field, especially the cheap ones, so there is an advantage to keeping them out of the guts of the audio gear. But there are many other sources of strong EM radiation in the world, so audio devices should be designed to be immune to them.

        That's why the ML 26 with PLS-226 is a bit of an eyebrow-raiser.
        Originally posted by Alrainbow View Post
        Lastly I tried many grounding methods as well to stop the hum.
        Hum caused by grounding issues is a completely different problem.

        Comment


        • #5
          I love your replies your a very high tech guy. Like joe Pittman very cool.
          Yes I guess redirect is like shielding but on other items example RFI it can be shielded. So for me to say they it's a shield it's a marketing ploy lol.
          In making servers I found emi and RFI to be issues it's how I got into this stuff. As for hum not really the stacking or EMI OR RFI is not always or mostly an apparent noise we hear IE hum. It's much more a glazing effect a loss of fine details. An example is a low bandwidth being used to stream. It looses resolution making it glaze.
          But induced noise on this network does not always sound like this.
          Cat 6 xxx is nit RFI shielded. But cat 7 is swap them and you may hear it. Try cat7 shielded and again an improvement may be heard if one grounds the shield on only one side.
          May I ask what you do for a living ? Your a very high tech person.
          speakers cust infinity IRS V , new caps and LPS , magnets etc.
          mark levivson pre no 26 amps no 33
          digital three cust servers , win ser 2016 , AO
          Dacs lampi various

          Comment


          • #6
            Answers in order of your quotes
            1- good play on words lol. For me shielding blocks to a degree is not. In your example removing the water on a floor is the same as redirecting where it lies lol.

            2- I'm not sure what's the difference here. I also used alum foil too. I even have some plastic that has micro faraday particles inside. MeAning an imbedded particles into plastic it helped to but not as much as all the above.

            3- yes it did as removing the outputs as well.
            I lifted the ground to no avail as well.
            Now here is one more oddity the left tube was worse then the right one was. And the transformer above was closer to the left tube below.

            4 too long to answer good read ty.but I can add add a few thoughts.
            Diodes emit noise too as do transformers and I hAve found taking the transformers out of the psu also lowers noise. This and diode bypass by both caps and chokes reduce this line noise. This I confirm with a scope. Plenty to be learned on this. Great read from you.
            yes left side has phono pre input if unit has the option
            my unit will be the phono unit in a third enclosure better then inside.
            the no 26 and 226 were Sota st the time and the fact some 28 years later they are still sought out and perform better then many exp new ones tells me something too. Of course I changed out all Elytic caps everywhere.
            This lowered the noise flour a few DB over all and was confirmed by a scope and signal generator weighted and non weighted.
            No hum was ever detected buy both by measurements and ultimately my ears tells me for about 100.00
            and my time was a very fruitful update.
            Many try legacy products. Amps in particular need new caps. Most don't and then claim hey that amp is not that good my new xxx sounds better lol. Get new caps then Compare.
            Also the speakers used do greatly effect the amps sound too. But this point can be proven in measurements as well as hearing it.
            5- yes agree.
            speakers cust infinity IRS V , new caps and LPS , magnets etc.
            mark levivson pre no 26 amps no 33
            digital three cust servers , win ser 2016 , AO
            Dacs lampi various

            Comment


            • #7
              Originally posted by Alrainbow View Post
              2- I'm not sure what's the difference here. I also used alum foil too. I even have some plastic that has micro faraday particles inside. MeAning an imbedded particles into plastic it helped to but not as much as all the above.
              Basic physics, you'll have to google a bit. You can have a magnetic field without an electric field, like with a permanent magnet (like Earth). When a current flows in a conductor it produces a magnetic field. AC produces an alternating magnetic field, which is fundamental to how a transformer works. When an AC magnetic field intercepts a conductor, it induces a similar AC current in that conductor. If the conductor is used for audio, you'll get hum. The shield of an audio cable (or CatXx cable) does nothing to block a magnetic field, but the twist of the wires and balanced drive/receive cancels the induced current equal in both conductors of a twisted pair.

              An electric field is more difficult to explain, but is a field produced around charged particle or group of particles forming a conductor. Its force is applied to other charged particles. The field can be blocked by a conductor, which is another group of charged particles.

              An electromagnetic field is a combination of both magnetic and electric fields, and radiates out into space. This is how wireless transmission works, radio, WiFi, etc. It can be bocked or re-directed by a conductor as well.

              Since your shielding was not magnetic, the field you're dealing with is not the magnetic field, but electric, or more likely electromagnetic. RFI is electromagnetic.

              3- yes it did as removing the outputs as well.
              I lifted the ground to no avail as well.
              Now here is one more oddity the left tube was worse then the right one was. And the transformer above was closer to the left tube below.
              [/quote]Removing the output of which device? Tubes sometimes vary in their susceptibility to EMI, but component failures can cause this too.
              Originally posted by Alrainbow View Post
              4 too long to answer good read ty.but I can add add a few thoughts.
              Diodes emit noise too as do transformers and I hAve found taking the transformers out of the psu also lowers noise. This and diode bypass by both caps and chokes reduce this line noise. This I confirm with a scope. Plenty to be learned on this.
              Diode "noise" is always bypassed by the ripple filter that follows in a PSU. If you look at the spectrum of that noise, you'd see it as primarily 2nd order (of the power line frequency), with harmonics falling with rising frequency. Completely normal, but all of that should be taken care of by the filter. If not, something is broken. The usual is capacitor failure. Caps can fail partially, or just be poor at high frequencies. Good caps come closer to the theoretical, but a high-value electrolytic often has trouble filtering high frequencies, so smaller value caps can be used across them. You'll see PSU upgrades that add those.

              Again PSU noise is a fact of life, having it radiate and interfere is bad design, or component failure. IF everything is working, and everyone has done their job well, stacking should not be an issue.

              Comment


              • #8
                The diode noise is more complex in part it's interaction with the transformer used and bad caps yes but they don't lower it if the caps are big as there ESR is too high
                so a someone poly .1 uf helps here but again all have consequences. Man your a high tech guy love this stuff.
                Lets talk some time please I'll make notes for talk points too. Ty
                speakers cust infinity IRS V , new caps and LPS , magnets etc.
                mark levivson pre no 26 amps no 33
                digital three cust servers , win ser 2016 , AO
                Dacs lampi various

                Comment


                • #9
                  Originally posted by Alrainbow View Post
                  The diode noise is more complex in part it's interaction with the transformer used and bad caps yes but they don't lower it if the caps are big as there ESR is too high
                  This is going a bit off topic. "Diode noise" is not actually noise, but a result of the modified input waveform by rectification. It does contain some higher frequency harmonics, but they are typically not radiated because they are filtered by a filter network close to the rectifier diodes. No, there's not that much interaction with the transformer, especially if the filter is good. Yes, ESR is a big factor in how good a filter is, but realize that the high frequency signals found around power rectification are not taxing to even the most ESR challenged filter cap. Today we have capacitors designed for switch-mode regulators, and those absolutely must have low ESR at 120kHz or so. There are good low ESR filter caps readily available. The low value bypass cap can mitigate the high ESR of a large value electrolytic. But I don't see that much in analog PSUs because generally the main filter is just fine. If it's a choke input, the ESR issues are less of a concern.
                  Originally posted by Alrainbow View Post
                  so a someone poly .1 uf helps here but again all have consequences.
                  Sure, but the consequences are mostly in terms of cost. No negatives in performances. Those who demand high transient current capability often will stack many smaller value caps (with very low ESR, DA, and resulting low DF) in parallel to get that result. You can also often spread out the required capacitor footprint horizontally that way, where bigger value caps get pretty big in height and diameter. I just worked on a headphone amp with 6 small radial caps in parallel in a PSU filter. They worked just fine.
                  Originally posted by Alrainbow View Post
                  Man your a high tech guy love this stuff.
                  Yeah, well...been at it for well over half a century. Head full of useless trivia.


                  Comment


                  • #10
                    Love it man making my brain wake up and think. So much of this was there but dust man.
                    Ty
                    speakers cust infinity IRS V , new caps and LPS , magnets etc.
                    mark levivson pre no 26 amps no 33
                    digital three cust servers , win ser 2016 , AO
                    Dacs lampi various

                    Comment

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