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Thread: Radford STA100 Restoration Blog

  1. #21
    montesquieu Guest

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    Quote Originally Posted by Radford Revival View Post
    The STA100 in its original form contains numerous minor design flaws. One of which is a zener in the power supply section that holds the bias rail steady. Sounds like a good idea in theory, but it actually makes the bias stability worse because you forgo the equal-but-opposite percent change in bias voltage to HT voltage as the mains fluctuates - meaning the bias currents are more at the whim of the mains voltage fluctuations than without it.

    Here is an original bodged power supply board (mentioned zeners not visible, some time in the distant past they were replaced and relocated to the underside of the board as a completely un-insulated zener string that could touch something else at any time, fantastic!)




    Here is my re-engineered board. The bias supply has been made entirely conventional with no zener regulation, high voltage fast recovery diodes used for the main supplies and fuses also accommodated. The layout has also been made much more logical. The original STA100 has many unintentional internal earth loops and they are known to hum and buzz themselves. I have since gotten one of these amps working and they are now completely quiet with my improved layout.

    That's fantastic Will. As you know I absolutely love mine (which you have with you of course at the moment) can't wait to hear it with these improvements.

  2. #22
    Join Date: Mar 2017

    Location: West Sūţsēaxe

    Posts: 2,015
    I'm Edward.

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    Lovely

    Put my name down in the hopefully orderly queue that is forming. I already sent you an email on this Will.

    Please consider putting the power switch on the side where the bias controls are. The 'front' side.

    Will you be adding the additional protection circuitry you did on my STA25?

    E
    Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)


  3. #23
    Join Date: Mar 2017

    Location: West Sūţsēaxe

    Posts: 2,015
    I'm Edward.

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    So we happened to be near Radford HQ last week, Will and Steve (Will's dad) kindly allowed us to visit.

    Will kindly played some music through a near completed STA100 to his RFC Raptor speakers.

    Absolutely magnificent. I could write lots of words but will confine it to following - massive presence, fluid, ease, dynamic.

    The amp itself is huge, as usual the rebuild Will has performed is impeccable. As is his workshop - neat and orderly.

    I was also very impressed with the RFC Raptors. Wide open sound able to convey music perfectly. The finish is first class.

    Overall to both items ...
    Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)


  4. #24
    Join Date: Apr 2012

    Location: South West of England

    Posts: 263
    I'm Will.

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    The amplifier has been complete for a while, but as the original anodised legend panels were a bit worse for wear, I had to spend a bit of time re-creating them in a vector editing package and have some fresh ones made. I will post a bit about that soon but for now here is the amp completed with the fresh panels! This amplifier also features some special output transformers of my own design.














    Last edited by Radford Revival; 16-10-2017 at 21:23.
    Radford Revival
    www.radfordrevival.co.uk

  5. #25
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

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    Wow!

    Gorgeous.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  6. #26
    montesquieu Guest

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    Beautiful work Will. Having seen the insides of mine this is night and day.

  7. #27
    Join Date: Sep 2014

    Location: Northern Ireland

    Posts: 1,403
    I'm John.

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    Ouch, that is almost painfully nice!

  8. #28
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 6,089
    I'm Alan.

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    Serious iron

  9. #29
    Join Date: Apr 2012

    Location: South West of England

    Posts: 263
    I'm Will.

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    Many thanks for the comments all

    Quote Originally Posted by Firebottle View Post
    Serious iron
    Indeed! Lifting these things requires planning, and I'm only half joking!
    Radford Revival
    www.radfordrevival.co.uk

  10. #30
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 99,005
    I'm Grant.

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    Superb work. Love the way these are put together. Bordering on perfecion
    Regards,
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