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Thread: Mythbusters does Hi-Fi.

  1. #11
    Join Date: Mar 2014

    Location: West Wales

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    I'm malcolm.

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    Thanks for the thread - looking forward to the myths getting busted.
    Audiophile Tosher

  2. #12
    Join Date: Mar 2017

    Location: West Sūžsēaxe

    Posts: 2,015
    I'm Edward.

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    Looking forward to having some myths busted. Also hope Jez you will give some hints as to what does improve sound.

    Sent from my SM-N910F using Tapatalk
    Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)


  3. #13
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

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    Quote Originally Posted by willbewill View Post
    Thanks for the thread - looking forward to the myths getting busted.
    Or verified?
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  4. #14
    Join Date: May 2016

    Location: Birmingham, U.K

    Posts: 351
    I'm Taz.

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    Thanks for this thread Jez, I will be following it with great interest.
    Often wondered whether there was any truth in a lot of the"tweaks" you mentioned so am glad someone like you has taken up this challenge.

  5. #15
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

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    After some thought I have decided that before going into the subject of SMPS, the bigger picture of power supplies in general needs tackling. I often see all sorts of confusion, false assumptions and 2 + 2=5 going on regarding power supplies (PSU's) so going back to basics is probably a good start. Some foundations are required before heading off in any specialised areas...
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  6. #16
    Join Date: Aug 2010

    Location: East Midlands

    Posts: 426
    I'm Hugh.

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    Fantastic idea Jez!

    Put your hard hat on and go for it, it's going to be a bumpy ride.

  7. #17
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

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    Sorry if this is patronising to many but to begin with I'll assume zero knowledge on the part of the reader...

    So what is a power supply and what qualities do we want from it?

    Everything powered by the mains needs a PSU (power supply unit) and even in the case of battery power, the batteries are then the power supply. A PSU is NOT only an external box which supplies power to another piece of equipment. It will often be built into the equipment and even in the case of an external PSU there will often be more circuitry associated with the power supply within the main unit.

    The perfect power supply will give a precise DC voltage which does not vary under any circumstances and has zero noise superimposed on the DC.

    Imagine a perfect 10V DC PSU. The 10V output would not vary with time, temperature, incoming mains voltage (if it's mains powered of course) and most importantly it will not vary with the current being drawn from it by the load.

    This last quality is known as a PSU's regulation. All PSU's, even batteries, have as one of their characteristics their regulation but this is not the same thing as having a voltage regulator... other terms such as the "stiffness" of a supply, its internal resistance, source resistance or source impedance all refer to basically the same thing. The perfect supply has 0% regulation, meaning infinitesimally low internal resistance. This means it would maintain exactly 10V whether it had no load on it or 1000 Amps being drawn from it. Think of the 10V being 10 foot of rope. It should stay 10 foot exactly even with 1000kg weight hanging of it. (I shall use analogy here and there to try and make things easier to grasp so apologies for the clumsiness of some of them! In this case the less than perfect rope would stretch to more than 10' but the less than perfect supply "sags" under the load and gets to be less than 10V...)

    Why is it so important that a PSU be "stiff", have excellent regulation etc?

    Imagine an amplifier with 3 stages of amplification, typically that means that at it's most basic we have 3 transistors (or valves) each with a particular gain (amplification factor). Lets say each has x 10 amplification so in total we have 10x10x10 = 1000 x amplification of the input signal.

    Now the problem is that an amplifier has more inputs than just the one labelled "input"... The point where each of the 3 stages takes its power from the PSU is also an "input", of much less sensitivity than the actual input but present nonetheless. Imagine that a 1mV signal in the form of a kick drum beat from a cartridge is the input. This will be amplified 1000 x and appear at the output as a 1V kick drum beat. The final stage obviously has the biggest signal as it's amplified by 10 by each stage and to give this 1V signal out the final stage must draw the most current from the PSU.

    If the PSU has poor regulation, ie is not "stiff" and has a high source resistance, then the 10V from the PSU will drop to lets say 9.9V in sympathy with the drum beat... The first stage is being powered from the same PSU and so it also experiences this drop down to 9.9V. The original 10V minus the drop to 9.9V gives us in effect another signal to the first stage of 10-9.9=0.1V or 100mV, 100 x more than the 1mV actual input from the cartridge! This will mainly appear at the output of the first stage, forgoing its x 10 amplification but still then being amplified by 100 x by the two following x10 stages.... In a severe case such as the example given we get "howl round" in the same way as a mic too close to the speaker in a PA system, but of course all happening in the electrical domain rather than via sound. (it would most often be at an ultrasonic frequency beyond even bat hearing in practice).

    Noise on the DC Voltage gets into the circuitry by the same method.... Note. In electronics "noise" refers to anything present which should not be there but is not related to the signal. So we mean mains hum at 50Hz, the frequency doubled rectification products at 100Hz, clicks pops, hiss etc etc

    Now, depending on circuit topology, real amplifier stages vary hugely in how susceptible to the above problems they are... in the degree to which their power input is also a signal input if you like. This gives us a figure called Power Supply Rejection Ratio, or PSRR. As a brazen generalisation, the simplest "purest" circuits with the fewest parts tend to have the worst PSRR (with the exception of a simple triode valve stage, which can have a useful degree of PSRR inherent to it. Still not that good in this respect though) and much more complicated circuitry is needed to give better inherent PSRR. Op amps tend to have extremely good PSRR.

    At the two extremes a very simple purist input stage for a very high gain circuit like a phono stage could require a really superb PSU to even work without obvious mains hum, hiss and pops and a state of the art PSU to sound really good. whereas at the other extreme some op amp circuitry could be powered by a really crap PSU with poor regulation and loads of noise and yet be impervious to it.

    It is important at this stage to point out that even in the case of the super sensitive phono stage example, if it had an external PSU as it often would, this PSU may not need to be particularly super-duper as filtering and smoothing , followed by a voltage regulator, would usually be inside the main phono stage and, if well implemented, can remove the noise and add the "stiffness" and excellent regulation we need at Point Of Load (POL) ie at the actual place we need it and often as physically close to this point as possible. An alternative but not good practice method used by some designers is to make the external PSU super duper good and forgo the filtering and regulation at POL. Now it can probably be easily seen that in the first case the quality of the external PSU is completely uncritical and could be expected to make little or no difference to sound quality or anything else.... In the second case the quality of the external PSU would be absolutely critical!!

    I guess the concept of obtaining good regulation by means of active voltage regulation using a voltage regulator circuit (or IC) needs tackling next... and unfortunately the concept of dynamic source resistance ie source impedance will also have to be dealt with, which I'm not looking forward to trying to explain!

    Sorry to technical types for all the ifs, buts, caveats etc I've glossed over or not mentioned but this is aimed at the layman.

    I'll let folks absorb that and answer any questions arising, things needing clarification etc before moving on
    Last edited by Arkless Electronics; 22-07-2017 at 19:11.
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  8. #18
    Join Date: Feb 2008

    Location: South Wales

    Posts: 9,151
    I'm NotTakingLifeTooSeriouslyTheseDays.

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    Good start Jez
    A...
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    Its now a conspiracy theory to believe that the Immune system is capable of doing the job it was designed to do.
    A fish is only as healthy as the water its swimming in ! [Dr Robert Young]


    www.tubedistinctions.co.uk

    Matthew 5:10

  9. #19
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

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    Quote Originally Posted by anthonyTD View Post
    Good start Jez
    A...
    Ta. It ain't easy as an EE to know just how much to simplify it, which areas people have the most difficulty understanding etc. This was really brought home to me the other day round at a mates house. He has a pair of Heybrook HB3's of mine on "permanent" loan and had placed some tapes on top of one. I pointed out that there are magnets on the backs of the speaker drive units and it may damage his cassettes. Now this mate of mine, who is a VERY clever chap but knows nowt about electronics, said to me "but aren't they only magnetic when the amps switched on and playing music"..... That's what I'm potentially up against!
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  10. #20
    Join Date: Feb 2008

    Location: South Wales

    Posts: 9,151
    I'm NotTakingLifeTooSeriouslyTheseDays.

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    Mind you, in the old days, with mains energised types,[or to put it correctly, types that used the smoothing choke as the magnet] he'd have had a point!
    Quote Originally Posted by Arkless Electronics View Post
    Ta. It ain't easy as an EE to know just how much to simplify it, which areas people have the most difficulty understanding etc. This was really brought home to me the other day round at a mates house. He has a pair of Heybrook HB3's of mine on "permanent" loan and had placed some tapes on top of one. I pointed out that there are magnets on the backs of the speaker drive units and it may damage his cassettes. Now this mate of mine, who is a VERY clever chap but knows nowt about electronics, said to me "but aren't they only magnetic when the amps switched on and playing music"..... That's what I'm potentially up against!
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    Its now a conspiracy theory to believe that the Immune system is capable of doing the job it was designed to do.
    A fish is only as healthy as the water its swimming in ! [Dr Robert Young]


    www.tubedistinctions.co.uk

    Matthew 5:10

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