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Thread: Mythbusters does Hi-Fi.

  1. #71
    Join Date: May 2016

    Location: Birmingham, U.K

    Posts: 351
    I'm Taz.

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    Quote Originally Posted by Bigman80 View Post
    I was actually trying to follow this. C'mon Jez, don't abandon us!!!



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    Thank you for trying to do this Jez, do hope you continue for the ones of us that were silently following. I am always looking to learn something new and this thread had me really interested.

  2. #72
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,861
    I'm Dennis.

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    Well there are potential outcomes from him continuing.

    He could provide very clear and accurate information showing most of us how ignorant we are, and may feel good after doing so.

    He may reveal his own limitations, which itself will be of use to all, and maybe even to him if he receives corrections.

    Just possibly, through debate, clarification of issues may result.

  3. #73
    Join Date: Nov 2010

    Location: Sheffield/Peak District. UK

    Posts: 574
    I'm Richard.

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    I wonder if it would be helpful to Jez if we made a list of phenomena that we found difficult to justify from a scientific view?
    e.g.:
    1. 'Electrons only flowing in one direction down a copper wire' - those cables with arrows on them to denote which way round they should be connected between two pieces of equipment.
    2. The whole mains debate (silver-plated fuses/plugs/cables/chokes/'smoothers' etc). (I hasten to add that I can understand the logic behind shielding cables).
    3. Are bits just a series of '1's and '0's? Do 'digital' cables have an effect? The possible effect of jitter.
    4. The effect of different isolating feet on amps, CD players, DACs etc.

    ...just an idea...?

    Thanks,

    Richard.

  4. #74
    Join Date: Feb 2008

    Location: South Wales

    Posts: 9,151
    I'm NotTakingLifeTooSeriouslyTheseDays.

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    I am sure Jez will come back to this at some point,
    Meanwhile, I will add my own 2 pence worth as far as the next step in power supplies, which Jez Started.
    Outboard power supplies, and when' if ever they are necessary.
    As can be see from what Jez has already explained in the first instalment, Stiff, low impedance power supplies are the goal we should all be aiming for, therefore; it is very important, especialy where high current is concerned to keep the power supply, and its regulation as near as posible to the circuits its supplying, and its something I have always tried to do in all of my own designs, however; where it can be a juggling act is when your dealing with low level signals such as phono-stages, where its always going to be a comprmise between keeping the power supplies as near as posible to the circuit, while maintaning enough distance between the mains transformer and the sensitive gain circuitry' to keep noise, and hum to a minimum.
    Even then you should always keep the final regulation as near as posible to the signal circuitry.
    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



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  5. #75
    RothwellAudio Guest

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    Ok, I'll add a further two pence worth on the subject of the stiffness of a power supply.
    Firstly, I think it always makes sense to consider the circuit which the power supply will be supplying power to. For example, a 100W power amp might draw only 100mA when it's idling but draw several amps at full tilt. On the other hand, a class A preamp might draw only 10mA - and it will draw only 10mA whether it's idling or at full tilt. So for the preamp there's no point in designing a power supply that will maintain the same voltage at 1mA current drain and 4A current drain because it will never see those variations.
    However, although the preamp's current drain is constant 10mA averaged over time its current drain is modulated by the signal it is amplifying. That means looking at "stiffness" slightly differently. The power supply must be able to supply the demands of the preamp's modulated current requirements while staying stable, and that means if the preamp is amplifying a 50Hz signal the current will be modulated at 50Hz, and if the preamp is amplifying a 20kHz signal the current will be modulated at 20kHz. Stiffness at DC isn't really an issue - it's stiffness at audio frequencies that matters.
    A crude unregulated supply would be a transformer, rectifier and smoothing capacitor. The obvious "audiophile" approach to improving this would be to simply have a bigger transformer, bigger rectifier and bigger smoothing capacitor, but examining the power supply's output voltage while it feeds a preamp which is amplifying a 10kHz signal might soon show you that you have just spent a lot of money for very little improvement. A much smarter approach would be to add a voltage regulator - the design of which is a topic for another day.

    The point I'm trying to make is that it's more useful to consider power supplies not so much as "good" or "bad", but rather "suitable" or "unsuitable" for the circuit they will be paired with. What's good for a power amp isn't necessarily good for a preamp.

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