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Avondale NCC200 mod

Discussion in 'd.i.y.' started by Mynamemynaim, Jan 10, 2020.

  1. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

    I know this is a well known mod ...but I just got round to trying it...and want to encourage anyone who hasn't been bothered to try it yet
    Replacing the 22k resistor next to TR1 with a 1k one ...to match the one next to it (NCC200 board)

    This is a Les W recommend change on these boards

    Really excellent improvement in my opinion...well worth doing for 10p cost for both boards...
    Clarity and bass notably improved
    Last edited: Jan 11, 2020
  2. mega lord

    mega lord Centre tapped

    Thanks for sharing that.

    I have been meaning to convert my NCC200 to 220 status (when i get round tuit) and that was one of the things to be done. I might just swap that one resistor first and have a listen before doing the rest
  3. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

    Yes..."the rest" can be quite involved, probably with a daughter board etc
    I'm certainty wondering if just the resistor mod ( I changed both on each board...just for a match) is most of the way to the improved sound...just because it's so noticeable..
  4. jagdesign

    jagdesign pfm Member

    Nice, might give this a go. Do you have a link to purchase said resistors?
  5. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

    Just standard 1k .... quarter or half watt ....1% or even 5% it's not critical...will be fine
    Mine came from RS

    eBay is cheap also...

    Ps...my 5% ones were within 2% anyway!
  6. jagdesign

    jagdesign pfm Member

    Great, thanks :)
  7. a.palfreyman

    a.palfreyman pfm Member

    I think i just put something like 3k3 across the 22k for ease. Definitely improves the sound. Don't know how to describe it but it seems 'cleaner' somehow.
  8. 337alant

    337alant Negatively Biased

  9. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

    Not sure the little blighters are 1w (not even Half that in that position!!)...but deffo 1%. But in that position..1% is not critical I just replaced both on each board and matched one board to the other (with 5% that were actually 2%)
    Really nice improvement ...and all thanks to Les's continued development of the original idea

    Ps. Yes other resistors at 1w elsewhere on the board ...but you won't get 1w legs through the board there without damaging something as the pads are quite small...
  10. Marra

    Marra pfm Member

    I think they are Welwyn MFR5's.
  11. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

  12. glenn jarrett

    glenn jarrett pfm Member

    Hi guys
    i have an ncc220 got the boards off Les
    and populated to standard spec
    is this resistor mod just for the quasi complimentary ncc200
    or the fully complimentary ncc220
  13. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

  14. glenn jarrett

    glenn jarrett pfm Member

    cool 1 less thing to mess with ;)
  15. 337alant

    337alant Negatively Biased

    Marra yes I think it was MFR5 that Les recommends, there isnt more than 20ma going through those 2 resisters so they don't need 0.75w.
    Thing I will have a go at modding my old voyager NCC200 output section to fully complimentary when I get time.

    [​IMG]A NCC 200 Vs 220 by Alan Towell, on Flickr

    [​IMG]IMG_1651 by Alan Towell, on Flickr

    Last edited: Jan 13, 2020
  16. GWM

    GWM Lost in the 70's

    I have to say I don't like 1K in that position,I got a set of early Qudos boards and fitted the values printed i.e. 1k and 22K.There was a discussion on the Qudos thread about changes to the circuit's values so changed my board in line, the result for me was a thin sound with a lack of body and a tendency to show up poor recordings more than I liked.In the end I tried some different values and ended up with 5K in the 22K position,this point is where the signal meets the feedback line so is sensitive.There has been endless discussions on the 22K resistor on the the various NAP clone threads on DIY audio, have a look at Biguns TMG10 thread.It's worth playing around with this value to tune your system to your own preference its surprising how obvious it is considering its only one cheap part.
  17. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

    Must admit I did consider putting a variable resistor in there from say 1k to 20k and having a fiddle to see what I liked best
    But just stuck the 1k in and was completely blown away with the improved sound ...no negatives that I could tell ... improved bass along with improvemed clarity win/win for me but as always... YMMV
  18. a.palfreyman

    a.palfreyman pfm Member

    I'm no techie so I am guessing a bit but the LTP splits the current (set at about 1mA) to about 0.5mA for each of Tr1 and Tr2. The 1k collector resistor of Tr1 then has about 0.5V across it to bias the VAS transistor, Vr4. If the collector resistor of Tr2 is 1k, this will have the same nominal voltage across it and therefore the Vce of both transistors is the same. Change the Tr2 collector resistor to 22k and this then drops about 10-11V reducing the Vce of Tr2 by about 10V and increasing the voltage swing on Vce of Tr2 compared to Tr1 so that these transistors are operating under slightly different conditions. Can any of the more technical amongst us confirm my suspicions please?
    I started this thread on the subject just over a year ago, related to another thread where I had seen this:
    I put 2k7 across the existing 22k to give 2k4 and it makes a noticeable and worthwhile improvement.
  19. nuit73

    nuit73 nuit73

    Is this mod on Avondale NCC 200 good for the Naim NAP Amp board.22k to 1K or another value like 2k7?
  20. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

    If your looking to mod naim boards / amps / preamps ...then the acoustica pages are the ones for you


    Not sure there is an equivalent resistor mod on the naim boards...but sure someone here will know!!

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