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QUDOS - the brilliant new amplifier boards from Avondale

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

  1. Jonathan

    Jonathan pfm Member

    getting on four weeks now ... the sound has gone through all KINDS of changes ... the high point apparently about a week ago - but now the lower (bass) registers appear to be getting far too thick and heavy(!). Funny how one never seem to hear complaints about TOO MUCH bass - i'm wondering if this is the result of using a wet tantalum capacitor for C6 AND C11 somehow (?) hmmmm ... maybe i need to do more fiddling ... or maybe the bass will settle down ... it would be interesting to do a bit of a spectral analysis going through the Qudos and another amplifier ... anyone else finding the Qudos bass heavy?
  2. Chops54

    Chops54 pfm Member

    Unfortunately no. My son couldn't bring the NCC200s Voyagers with him but we spent plenty of time with the NCC220s over Christmas. I also had a friend over who has a pair of original Voyagers and the opinion was overwhelmingly in favour of the 220s. For me they have a delicacy that the 200s can't match.
  3. divedeepdog

    divedeepdog pfm Member

    I've probably got the last NCC200 Voyagers built, BUV20 output devices + HCR's on the front end. Les has advised NCC220 will be better...Hard to believe they can get better :D
  4. Chops54

    Chops54 pfm Member

    I have a stash of BUV20s and I was going to upgrade my 200s when the 220s came along. I might still do that if I can prise them from him for long enough. I’ll probably have to lend him my 220 Voyagers and that will be last I see of them no doubt!

    I should have mentioned that I’m still using the old VBEs with my 220s. As I’ll be moving up to NCC300s sometime soon I couldn’t see the point in changing them.
  5. Anyone got these boards in a 250 with the HCR boards? I’m interested in what improvements you would get over the standard boards. I’m not sure whether to get them so soon after having the standards boards serviced.
  6. flashgo

    flashgo DIY Practitioner

    Yup, they'll blow away your serviced boards. The only downside is that both the NCC220s and HCRs generate heat, so be prepared for a warm box. OTOH, you don't need to keep your amp on 24/7. I find I can just turn it on when I want to listen, and it sounds great in very little time.
  7. Thanks. Normally just turn it in when listening as well.
  8. Jonathan

    Jonathan pfm Member

    odd - i dont' find mine any warmer than the original NAPA boards even at full 'clip' ...
  9. Forgot to ask, but did you get them with the Avondale voltage levels?
  10. andrewsutton

    andrewsutton pfm Member

    I have been running NCC220s in a Voyager layout and am thinking of adding an HCR200 to each monoblock.
    I can’t seem to find a layout including HCRs and can’t remember where the HCR 0v line connects to the Cap6. That is rectifier or amp end.
    Is there any consensus on this?
    Really pleased with the NCC220s!
    Cheers Andy.
  11. flashgo

    flashgo DIY Practitioner

    I built the NCC220s and purchased the HCRs pre-built. I remember setting the the 220s to the then popular bias current. I'll have to go back in and check things at some point. The HCRs provide the bulk of the heat inside the 250.
  12. Jonathan

    Jonathan pfm Member

    running mine at 100mA or thereabouts ... what are others doing?
  13. peterm

    peterm pfm Member

    120 mA total quiescent per channel as per Les's recommendations (NB NOT the same "popular bias current" as for the NCC200s).

    Case gets noticeably warm (not hot) during operation, playing music or just switched on.

    I think this is because Les intends this amp to be biased more heavily into Class A, with the bias transistor mounted on the output device's heatsink affording a measure of "self regulation" in case output starts to get too high.

    As Les told me when I ordered the NCC220s "if you listen at moderate levels you might be listening entirely in Class A".

    He recommended switching on half an hour before serious listening and switching off when not in use.
  14. Jonathan

    Jonathan pfm Member

    i thought 100mA WAS already a bit on the 'hot' side of the 'current curve' ... okay maybe i'll try cranking things up a little and see what happens
  15. peterm

    peterm pfm Member

    I believe that Les now sells his ready built modules (and theyr'e a beautiful piece of work) ready adjusted so that no set up procedure is required, they are self regulating so long as you don't try buggering about with them too much!

    It's been reported that they have a smoother, sweeter, sound than the NCC200s but they have even more detail, but not in an aggressive way.
    That's been my experience anyway.
  16. Yes he does. I bought mine ready made with bias set and instructions not to touch it. Just plug in and play. The difference from the original Naim boards is astonishing. Bags of detail and clear bass. I’d describe my amp as Luke warm after being on an hour. It doesn’t differ in temperature after that and I always switch it off after use as it can be a week before it’s used again.
  17. Pine Marten

    Pine Marten pfm Member

    I agree with The Man..... had mine for about 9 months now, with minicap 6 psu boards in monoblock ex 110 cases. I guess mine run at a "moderate" level, cases are at ambient temperature even after 3 or 4 hours use. Been "on" since 9am today, switched off at 12 midnight, just warm to the touch, and this is in a pretty tight space too. I only use my system at the w/e so on Friday, everything gets turned on about an hour or so before I want to listen. On a saturday however, I have R4 on from say 9am, so by serious music time, say 8pm everything is well warmed up. Cant with all honesty say it sounds any different having been working for hours on a Sat than it does for just a 1hr warm up on Friday. BTW, also do the same with the HICap, 32.5 RSL, Caiman DAC etc. I like a warm house, so the gear s never really cold!
  18. 337alant

    337alant Negatively Biased

    It wont be the wet tantalum's could possibly be too much capacitance on your output Cap6 bank ?, what did you put in there ?
    It could also be that you have just discovered the real sound of your loudspeakers ?

  19. Jonathan

    Jonathan pfm Member

    yes - could be (the real sound) ... though this sounds quite a bit different from any of my other amplifiers ... in the bass register ... though honestly i didn't know my little audio physic tempos were CAPABLE of such bass ... I try not to turn it up too loud.

    I'm not sure i understand your question about the wet tants ... how would they be 'too much capacitance' compared to any other 68µF capacitor ...? or maybe i misunderstand ... not using a cap 6 (rather four 15K µF caps at the moment) - i do have some minicap 6 boards though I will try later ...
  20. peterm

    peterm pfm Member

    Here's a new development, Les is advertising pcbs & odd parts for NCC200s on eBay,

    Note that these are version 1.5!
    And TR5 is on the heatsink like the NCC220s, with bias set to 120 - 140 mA.

    Output devices are still MJ15003 in quasi complementary configuration.

    Not sure what to make of this!

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