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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: 715
    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.

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    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: 715
    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: 715
    I'm Sandro.

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    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: 715
    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: 715
    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

  8. #238
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 715
    I'm Sandro.

    Default

    Hi there

    It has been pretty quiet here lately
    Life happens outside this thread
    Any way there is no point posting whit little to report, a catch-up post is now well due.
    I had a call Martin a few weeks ago both amplifier dead or dying WTF?
    Back ground
    Those have been running for nearly 2 years now driving a pair of, most excellent, W.B. Discoveries whit the best sounding “Polk Cobra” Cables
    I am not sure of what was happening and what caused the problem, I was not there, but as it turns out one of the mono blocks was blowing fuses and the other one had smoke and discoloration on the Fukushima Futaba plate resistors on the CRCLC supply circuit.
    Not sure if it was a passive pre whit a DAC supplied by a car battery a fault whit the mains or the Cobras causing oscillation, what strange is that both amplifiers went at the same time.
    At first look the boards Mossfet and Jfet look ok
    Martin is drooling over the Fairchild I have and may new 10 U PCB’s that wont fit, why?
    Any way we decided as I had the amps to bits to build a new Plinth and in the process to get rid of over 25 Kg of 100-year-old slate
    I am a point when we will start to build them back so here are a couple of teasers

    DSCF2788.jpgDSCF2789.jpg

    It should be ready pretty soon I hope
    As Martin is not listening to his FiFI at present as the spare £6K Musical Fidelity he has "sound like shit"

  9. #239
    Join Date: Aug 2018

    Location: Liverpool

    Posts: 18
    I'm Martin.

    Default

    I blame the dog for it spontaneously deciding it didn't want to work, either that or the massive amount of refurbishments going on in our street and our recent power outages.

    I do want the Fairchild's, but for good reason. The matching is incredibly close and I would be surprised if I could get some as closely matched as your set BKsabath.

    They are going to be better than ever in any case so every cloud has a silver lining I suppose.

    Thanks for the help and the Fairchild's mate

  10. #240
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 715
    I'm Sandro.

    Default

    Cool by me, at a price pity the 10 U boards do not fit I have made them for 400 mm heath sinks

    As soon as the mods are done I am going to get them going whit the IRF. I could not find any faulty part so far, your Jfets and such seems ok lets see what up
    2 things came to mind
    1) I am looking forward to compare the IRF 240 9240 whit the Fairchild's on my new ones then maybe swap them after a one to one comparison.
    So my plan would be rebuild yours whiteout changing to much see what happens when you got them back as you may kill them again
    I would look for the compensation for the Cobras. I believe Nelson wrote about it as he likes those cables a lot
    Then when mine are done and you really like them I can lend you the my old F5's while we swap the power stage if you can't bear to have to listen to the MF
    I am planning to re do the Input boards as well whit the 10 U copper weight, those would fit and I want try the new linear system Jfet so it may be worth doing it this way?

    hey what up whit the Musical Fidelity amp any way what is wrong whit it ?

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