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QUDOS - the brilliant new amplifier boards from Avondale

Discussion in 'd.i.y.' started by misterc6, Jul 10, 2017.

  1. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    I was recently pleased to be given the opportunity of building and testing a pair of new power amplifier boards from Avondale Audio. They are an improved version of the well regarded NCC200 boards and were originally given the designation NCC220 although Les has now opted for the name QUDOS to better differentiate them from their predecessor.

    The main differences are that these have a fully complementary output stage rather than the quasi-complementary stage of the NCC200 and have the option of fitting the bias transistor on the main heat sink. A higher level of bias is possible with this arrangement and I'm currently running them at 120mA compared to 38mA on the NCC200.

    I've had wide experience of Naim NAPA boards, modified NAPA boards and NCC200 boards but can report that these new boards blew me away from the very first moment I powered them up. The music just flows effortlessly from them and I'm hearing things in familiar tracks that I've never heard before. They are particularly impressive in the way they render percussion and vocals. The intro of Blondie's 'The Tide is High' sounds so much better than it ever has before and I'm listening to Keith Jarrett's 'The Köln Concert' in a new light as I type this.

    I'm currently running the boards with the +/- 39v rails in my Naim NAP110 mono amplifiers and, from previous experience, I'm looking forward to trying them with higher voltage rails.

    I'm not sure what Les' intentions are about putting the Qudos boards into production but I can definitely recommend them very highly.

    [​IMG]IMG_0903 by Malcolm Connah, on Flickr

    [​IMG]IMG_0905 by Malcolm Connah, on Flickr
  2. James Evans

    James Evans Bedroom Bodger

    Thanks for sharing that Malcolm. Looks interesting. Are they 15003/15004 pairs on the output? How warm do they run?
  3. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    Yes, the output transistors are MJ15003 & MJ15004. I haven't measured any temperatures but have had the boards powered up 24/7 without noticing any difference to the previous boards which were modified NAPAs. Obviously the idling temperature will be very slightly higher due to the increased bias current.
  4. jirka

    jirka pfm Member

    How hot do they get when driven high after an hour or so at ambient temp of 25 ?

  5. S-Man

    S-Man Kinkless Tetrode Admirer

  6. LesW

    LesW Making electronics make music

    Check out the TO126 device on the heatsink
  7. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    That's the bias transistor it can be fitted where the blank pads are or on the main heat sink, I chose the latter.
  8. LesW

    LesW Making electronics make music

    It depends on what you're driving and at what level also, the surface
    area of heatsink in free air.

    In effect, no hotter than the amp I made that you're using right now.
  9. S-Man

    S-Man Kinkless Tetrode Admirer

    Is it tracked to duplicate TR5, or do you need to wire underneath the pcb?

    Anyway, nice work Les.

    FWIW I have a NAP/NCC type amp with Sanken LAPT complementary outputs.
  10. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    It's tracked on the top surface of the board.
  11. jirka

    jirka pfm Member

    Will it be an upgrade on the ncc200 if trials go ok ?

    What voltage tranies would be required and caps ?

    While on the subject of upgrades has the HCR 200 been a success on trials .
    Not spotted any feed back on them on here to date .
  12. chiily

    chiily PFM Special Builder

    Those look a neat drop ins for the NCC200s. Looking at the board they look simple to Voyagerise.

    I do hope bare PCBs will be available, I enjoy building stuff :)
  13. Dowser

    Dowser Learning to bodge again..

    Very nice!
  14. grazie

    grazie pfm Member

    Thanks for posting Malcom (and Les). So you're saying they sound that good compared to everything else you've heard? Only asking for clarification as that is a very simple looking (comparatively) power amp.
  15. russel

    russel ./_dazed_and_confused

    Are they emitter follower outputs or sziklai?
  16. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    As I said in my original post I am only comparing them with standard NAPA boards, modified NAPA boards and NCC200 boards. I was stunned when I first powered them up and several weeks later, having listened to a wide variety of source material, remain entranced.
  17. LesW

    LesW Making electronics make music

    From Jirka:

    Will it be an upgrade on the ncc200 if trials go ok ?

    Only time will tell if it becomes as widely accepted as has the NCC200

    What voltage tranies would be required and caps ?

    Suggest a max of 50-0-50 VDC as with the NCC200s

    While on the subject of upgrades has the HCR 200 been a success on trials .
    Not spotted any feed back on them on here to date .

    They're quietly gaining ground and several have been installed by Witch Hat
    during servicing of 250s. Feedback can be read on the Avondale Audio Facebook page.

    Here's a review sent to me by Witch Hat as received from a customer of theirs:

    I would like to say thank you for the amazing job you did on my Naim 250. It was serviced and you installed Avondale NCC200 and HCR200.
    The sound is absolutely amazing, the Naim PRAT is totally retained, but there is stunning amount of musical detail audible on everything that
    I have played through the system. The bass is deep and controlled without being bloated, and the hiss from the speakers has gone.
    Totally recommend this upgrade, along with the Avondale 821 cards which I also installed into my Naim 72.
    The amps totally smoked my my mates Naim 82, HiCap and 135s, all recently serviced by Naim themselves. I would like to add that I do use
    the Avondale TPX1.5 in place of the HiCap. Thanks again guys. DR
  18. divedeepdog

    divedeepdog pfm Member

    I've got HCR 200's in my amps, they're a bit special :D
  19. LesW

    LesW Making electronics make music

    I'm sure you're not suggesting that only the most complicated circuits have
    any merit when it comes to sound quality.?

    Have a listen to a Nelson Pass class A amp for instance - as simple as it gets.
  20. grazie

    grazie pfm Member

    :D :D :D

    Been thinking about building the Nelson Pass for ages. It'd be an extra source of heat, if nothing else in the coming winter months. I've already got a pair of heat sinks (radiators)....plus more bits, I think.

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