1. Things you need to know about the new ‘Conversations’ PM system:

    a) DO NOT REPLY TO THE NOTIFICATION EMAIL! I get them, not the intended recipient. I get a lot of them and I do not want them! It is just a notification, log into the site and reply from there.

    b) To delete old conversations use the ‘Leave conversation’ option. This is just delete by another name.
    Dismiss Notice

QUDOS - the brilliant new amplifier boards from Avondale

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

  1. Mike Hanson

    Mike Hanson Really?

    Thanks for the clarification, Peter.
  2. steveinspain

    steveinspain pfm Member

    I've just ordered some Qudos modules, and Les has told me that the only thing I need to do is a simple test with a multimeter, and that in use the amps can be left on at all times as there are no parts to degrade.
    So far I don't know what that test is, but I got the impression that it's not as complicated as setting the bias (not that I even know what bias is, or how to set it..)
  3. Mike Hanson

    Mike Hanson Really?

    Setting the bias is actually very easy. You attach your multimeter to a couple of test points, and measure the current without speakers attached. You use a little screwdriver with the potentiometer to adjust it up or down, as necessary. You try to get it to stay "close" to the right value for 20 minutes or so.

    If you get to that point, just check back and we can give you further instructions.
  4. steveinspain

    steveinspain pfm Member

    Thanks Mike - much appreciated!
    Out of curiosity, what is bias, and why does it need adjusting?
  5. Mike Hanson

    Mike Hanson Really?

    That's a hairy question, as it involves amplifier class design, and the limitations of each. For more info look here: https://www.electronics-tutorials.ws/amplifier/amplifier-classes.html.

    Suffice it to say that the bias needs to be at a certain value, and the variations in the components on the board will cause some inconsistency from one board to the next. The bias setting lets you correct for those. so you hit the right value.
  6. steveinspain

    steveinspain pfm Member

    I'll have a read, and see if any of it makes sense to me...!!
  7. DavidR

    DavidR Member

    Hi I have just received mine, I was a bit jittery about the install process myself, just call Les, and he will advise you on whatever you need to know, in fact I have just spoken to him myself. I will be installing mine tomorrow.
  8. steveinspain

    steveinspain pfm Member

    Good luck and hope all goes well - it would be good to hear how it went and how good they sound..!
  9. Jonathan

    Jonathan pfm Member

    Just curious what people are thinking of their qudos builds ... it certainly takes a little while to burn in ... I’m finding mine surprisingly bass heavy ... which is kind of neat as my speakers are doing things they never did before but I’m finding the general balance so far from other amplifiers I’ve had a BIT disconcerting. Maybe it’s the wet tantalums I used ... just curious what others are finding.
  10. DavidR

    DavidR Member

    Just installed a new pair of Avondale Qudos boards into my Naim 250, ( upgrade from the NCC200 boards which were previously installed ) Also previously installed were a pair of Avondale HCR200s. The sound before was as good if not better than a NAP250 DR, this should bring it close to a 300DR in performance. A few weeks to run in should tell, but early indications from half an hour after switch are VERY promising. I will update as the burn in period progresses. Certainly no bass heaviness or balance issues in my system.

  11. steveinspain

    steveinspain pfm Member

    What do the HCR200's do and or replace, and what's involved in installing them?
    My amp (a zap 250) has these bits - 2 x NAIM NAPA4 power amp boards serviced by Avondale and SOA components removed.
    2 x 350VA toroidal transformers
    2 x MiniCap6 rectifier/smoothing boards.
    So which bits are the HCR200's replacing, and are they plug and play?
    As always, thanks for any help!
  12. DavidR

    DavidR Member

    Hi Steve

    This link may help

    I am no electrical engineer myself but the following article may help.

    They are certainly no more difficult to install than the Qudos boards I put in today. Pretty much plug and play really.



  13. steveinspain

    steveinspain pfm Member

    Thanks David - when wading my way through this thread (OK, looking at the pictures as I don't understand most of the writing..) I had assumed that they were the amp part.
    I'm away for a few days but think I need to talk to Les on my return and find out a bit more..
    I really am out of my depth here as even the less observant will have noticed!
  14. nn_in

    nn_in New Member

    Which are the Avondale pre-amp that can run with Qudos .
    Also does the minicap influence the sound significantly or standard DC amp power supply is ok.
  15. andrewsutton

    andrewsutton pfm Member

    Les does boards for preamps primarily designed as drop in replacements for Naim boards. A number of folk here have used them to build a preamp but power supply, volume control and switching will be the minimum additional requirement from an electronic point of view.
    Power supplies are complicated and how they are built and wired into your amp can be critical.
    Getting that bit right is more important than the capacitors etc in such boards. I would be surprised if Les’s boards are not right. Others may be problematic.
    I recommend a website called Hifisonix where you can find an article on how to wire up an amplifier. Messing up the 0v connections around reservoir caps can add orders of magnitude to distortion.
    Cheers Andy.
    nn_in likes this.
  16. scolarest

    scolarest pfm Member

    My own recommendation would be a Avondale's Grad One. They are as rare a hen's teeth but a sleeping giant among pre amplifiers.
    A proper keeper!
    nn_in likes this.
  17. 337alant

    337alant Negatively Biased

    Les Also does the 821A pre amp boards , just add a quiet power supply

  18. 337alant

    337alant Negatively Biased

    Steve the HCR-200 are is a simetrical regulated power supply
    To run an NCC-220 power amp boards you need the following
    Transformer - Cap6 or minicap6 - NCC-220 power amp boards
    For stereo you need 2 of everything

    For enhanced regulation of the power supply you can use the HCR200 as follows
    Transformer - Cap-6 - HCR-200 - NCC-220.

    An alternative (and the best IMO) is to only regulate the front end supply as in the Voyager mono amps so you then need split the NCC-220 amp rails so that the front end stage is powered separately to the output section
    You then need 2 power supply's per channel to power the front end separately to the output
    Output transformer - Cap6- NCC-220
    FE transformer - Minicap6 - HCR-200 - NCC-220

    divedeepdog likes this.
  19. steveinspain

    steveinspain pfm Member

    Thanks Alan - a lot of that is way over my head but I have ordered a pair of HCR200's to go with a pair of NCC220's - all of which I'll be getting in a few days.
    Having never done more than opened up an amp to have a look it'll be a learning curve, but Les seems so clear and helpful that I'm sure I'll get it sorted - I may even buy a soldering iron so I can feel like a qualified DIY section member...
  20. 337alant

    337alant Negatively Biased

    Les is very helpful and you will get plenty of support from here as well , just ask;)
    Post pictures as you go before switching anything on


Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice