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Thread: The Bug is back

  1. #231
    Join Date: Nov 2020

    Location: London

    Posts: 17
    I'm Max.

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    Are these motor run caps?
    Obtaining mains transformers is a pain now, toroidy doesn’t appear interested in quoting for small orders and Canterbury Windings is booked out for months… maybe it is indeed time to go smps for class a amps, as some on diyaudio are doing.

  2. #232
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 604
    I'm Sandro.

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    0900766b81717062.pdf (rs-online.com)

    Rifa PEH200 on this build only 36 X 22000 uF

    Never had any problem ordering Toroidy via the web site, do not ring the grumpy old git and ask for discounts he is a grumpy old git and try to charge you more.
    Once you place the order Pay pall take care of the rest
    Tips
    When you order them get the bases and ask for no badge normally they are in the bag and one can fit them after so that they are straight

    I have made the mistake to get traffos from the like of Canterbury windings and it was a big mistake as they buzz a lot. If you do you must specify no noise for audio use vacuum resin impregnated 12 times and good luck whit that, which is a pity because I rather buy the gear from here even if it was a bit more expensive

    You are only going to buy the trafos once in a life time so get the best you can

    There are other decent brands out there but either they cost 2 times as much or are not half as good as the Toroidy + one have to pay custom duty and that pisses me off, even better order them now or you may end up paying custom and such in a few months

  3. #233
    Join Date: Nov 2020

    Location: London

    Posts: 17
    I'm Max.

    Default

    Thanks v useful. Maybe you ordered from toroidy before the start of this year? You cannot web-order to the uk anymore, you have to email for a custom quote. And there should also be import duties unless the order is beneath… £150?? Not sure what the threshold is.

  4. #234
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 604
    I'm Sandro.

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    Ops my last order was in November 2020

    I got trafos for paradise as well may change depending on "current situation" I hope

    Maybe dude was selling to many to the UK

  5. #235
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 604
    I'm Sandro.

    Default

    DSCF2753.jpgDSCF2754.jpg

    PSU fully wired and tested
    It is on the bench powered up
    I am going to live it on for a while on no load to form the capacitors
    Rails are all at 40.62 Volts, no load, those tarafos are so good

  6. #236
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 604
    I'm Sandro.

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    I am still working on this do no despair
    Second pass of matching and the last 200 on the bench as we "speak"

    I have stopped any purchase of parts from China due to "the current situation" AKA the Fauci virus




    DSCF2764.jpg
    DSCF2765.jpg
    DSCF2766.jpgDSCF2767.jpg

    I have made same small modifications to the test rig
    as you may notice I now have 3 pots to dial in the VGS the central one is a 1K 25 turns that let me dial in the 500 mA current precisely
    at the risk of repeating myself I am measuring the VGS at 500 mA 30 V 50 C

    The bottom most white board has 200 Fqa19N20C whit VGS from 3600 to 3700 mV

    On the bench a further 200 FQA12P20 Vgs around 3800 mV

    VGS can and is I have found up to 4700mV on other batches I have

    The lower the VGS the higher the GM or gain of the mossfets

    It looks like I struck gold whit those low batches
    yes there is 200 mV difference between the N and P sides and I have asked same help to a reputable source

    I copied in the email

    >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

    Very nice build. [IMG]file:///C:/Users/Sandr/AppData/Local/Temp/msohtmlclip1/01/clip_image002.gif[/IMG]

    You are not realistically going to get the same Vgs and Gm figures from N and P types,
    so we have learned to settle for matching within polarities.

    If you want to try to address this, you can use different quantities of P vs N, or alternatively
    adjust Source resistor values. In the Pass Labs forum at diyAudio Lynn Quam has shown yet
    another approach with his SIT3X circuits, where the drive to complementary types is altered
    a bit with local “Schade” feedback, and he gets some good results.

    It’s a relatively minor problem, but interesting to pursue.

    As to interviews, I just respond to invitations, although lately I need to be careful of being
    over-exposed....

    best,

    np

    >>>>>>>>>>>>>>>>>>>
    so as soon as I have tested again the P channels
    I should be able to pick the best matches and solder them on

  7. #237
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 604
    I'm Sandro.

    Default

    DSCF2769.jpgDSCF2770.jpgDSCF2771.jpgDSCF2772.jpg


    I have finished matching the FQA12P20

    I have groups of matched massfets at 500 mA in 10 mV rows

    I am going to use the DCA Pro to pick the quads I need
    On the graph the 4 that are going on the board's for one channel
    of the 17 I have that measure up at 3.840 V I got 3 very good quads
    Victory !!! well almost there
    I am whacked for today so I am to call it a day

    Besides I got an invite to "world fist listening session"
    If I get permission, you may be in for same HiFi porn later

    PS

    From picture 1 quite a few rows there for quite a few super duper quads

    I got spares

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