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Avondale NCC300 amp project ..

Discussion in 'd.i.y.' started by laverda, Feb 28, 2018.

  1. MarkieW

    MarkieW pfm Member

    Out of interest S-Man, how many hours/days would you say it took before the NCC300s came on song?
  2. S-Man

    S-Man Kinkless Tetrode Admirer

    Sorry, I cannot answer that. I tend to assume that amps (caps) are run-in after they have been through my various bench tests for several hours.
    Then I alternate new amps with existing references at fairly random intervals. Sometimes the new amp is powered up all day, sometimes only when listening.
    Sometimes I think I hear the sound change over time, however I often try a few different cables to try to optimise the sound.

    So it's all a bit vague and non-scientific, but the final arbiter of sound quality is "does it stay in the system?".
    Mynamemynaim likes this.
  3. df_genius

    df_genius Solder slinger

  4. 337alant

    337alant Negatively Biased

  5. Chops54

    Chops54 pfm Member

    I finally moved my NCC300 downstairs into our main system. It has spent a fair while on the floor in my bedroom because I preferred my NCC220s in the main system. I had it on all day yesterday and I could take it or leave it tbh. Today things are very different. I’m on cd number four and Alison Goldfrapp sounds like she’s in the room with me! This is the first time I’ve sat down and listened to Felt Mountain all the way through without getting bored.
  6. df_genius

    df_genius Solder slinger

    Yes and those transformers have separate secondaries for the driver and output stages, I have ordered two for my NCC300's
    337alant likes this.
  7. Jo Sharp

    Jo Sharp Pulls on doors marked push

    Big Plus 1 for R-Cores powering the front end circuits.
  8. Mynamemynaim

    Mynamemynaim 38yrs a Naim owner

    Would those transformers also be good for the front end of a voyager 220 ?
    They look (fairly) compact and I must get round to splitting my ncc220 into a voyager
  9. Paddy

    Paddy pfm Member

    I wonder what the benefit is of R cores and why Les might not have used them?
    Mynamemynaim likes this.
  10. john.luckins

    john.luckins pfm Member

    Benefits are low capacitance between primary and secondary windings (a problem for toroids) and a low hum field, similar to that of toroids. I would guess that the scarcity of R Cores and their cost is the major stumbling block for Les.

    Here's one I got hand made in Thailand at Christmas...

    337alant and mega lord like this.
  11. 337alant

    337alant Negatively Biased

    You only need a 100va tranny for the front end with a 42 - 0 - 42vac secondary for a monoblock (in this case I used 44-0-44)

    [​IMG]IMG_3318 by Alan Towell, on Flickr

    Mynamemynaim and Mike Hanson like this.
  12. say it as it is

    say it as it is pfm Member

    so R Cores better than Toroid or O core then?
  13. S-Man

    S-Man Kinkless Tetrode Admirer

    I have a confession to make... I had become a bit jaded with the sound of my NCC300s, this has been partly caused by strapping Les' giant EI-core transformer into my Leach amp and getting a very nice improvement in sound. THe NCCs had.s a slightly strident upper midrange, which is common in very many SS amps IMO. I always thought the Leach somehow managed to avoid this, which is why it has been my reference amp for many years.

    Anyway, in an effort to design out this "edge" to the sound, I stared investigating the performance of the regulators. The current result of this is that the regs are out of circuit in my amp (the regs are not to blame for the edge) and I'm running with good old fashioned R-C decouping on the front end.

    The NCC was powered by a pair of Yamaha EI-core transformers, which I had always thought were pretty good. I estimate they are about 200VA each.

    This afternoon I decided I really ought to try the giant EI in the NCC300s. I can't quite believe what I'm hearing. It's bloody amazing!!!!!
    Leagues ahead of any of my other amps. The NCC is clearly much better than the Leach - now this it has the right transformer in it.

    I still cannot understand why a transformer should affect the sound so much, but who cares? It pleases me greatly!

    If I was JMH I would now have to write:
    "The revised NCC300 has caused me to have to completely revise my usual subjective scoring system. Previously an item that scored 86 points would only score 36 points on the new system. Please take this into account when comparing this with older reviews...." :D

    NB Thanks Les!!
  14. mega lord

    mega lord Centre tapped

    This echoes my findings completely (but not with Avondale amps). I don't have a giant EI core but am using the little EI's that Les uses on the front ends of the voyager to power the whole amplifier - twin secondaries @ 25-0-25V. I prefer them to my Canterbury Windings toroids 350VA 35-0-35V with separate winding for the front end.

    No resistors or inductors between smoothing caps and it also sounds better with no regulator on the front end. Currently I am using NVA amp boards (six of) that Richard Dunn kindly sold me a few years back. He warned me they neither needed nor wanted any regulators. I didn't believe him so tried some HCR200 regs on them. Went back later to no regs and preferred it. The nva circuit is similar to the Avondale in many ways but not designed properly apparently :rolleyes:

    No contest - EI is where it's at.
    337alant, S-Man and Mynamemynaim like this.
  15. S-Man

    S-Man Kinkless Tetrode Admirer

    I've never been a fan of Rs or Ls between smoothing caps. Tried it multiple times, measured the reduction in ripple and noise on the rails, but never liked the sound :confused:.

    I will try reinstating the front end regs and see what it does for the sound. It's certainy easier to achieve a minimalist build if they are not needed.

    Problem is now that I need to rebuild the NCC in a new case, to fit the EI lump in!

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