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NCC300 Dual-Mono in a big Case

Discussion in 'd.i.y.' started by Mike Hanson, Oct 21, 2021.

  1. Mike Hanson

    Mike Hanson Lovely!

    My other NCC300 build uses 2U Dissipante cases, and Les said it was was easily able to handle everything the NCC300 would need. He even suggested I use a higher voltage, given the heatsinking ability.

    This build is twice as tall at 4U, so I don't think I'll have a worry. :D
     
    Gervais Cote likes this.
  2. Mynamemynaim

    Mynamemynaim 38yrs a Naim owner

    Mine are in a pair of 2U dissipante cases too and they barely run warm never mind hot...and I'm at 60v regulated to 55v and 125mA
     
    Mike Hanson likes this.
  3. OldSkool

    OldSkool pfm Member

    A bit of an aside, but looking at the NCC300's themselves I can see they have a 47uF 100V electrolytic next to the 0.22R emitter resistors. I'm guessing this is local rail decoupling for the output transistors. I've bought some 470uF's for my dual transistor Qudos build, as per the HackerNap design, interesting that Les has perhaps included these on the 300's but of a smaller value?
     
  4. Gervais Cote

    Gervais Cote Predator

    60v, that’s a lot ! Must be very dynamic !
     
  5. Mynamemynaim

    Mynamemynaim 38yrs a Naim owner

    It's nothing short of brilliant
    Les is to be commended on another excellent amp ...I honestly believe a Naim 300dr would not better the control and clarity these amps are capable of
     
    Gervais Cote and Mike Hanson like this.
  6. laverda

    laverda pfm Member

    perfect....
     
    Mynamemynaim likes this.
  7. geoturbo

    geoturbo pfm Member

    Speed this up, Mike! We'd like to hear how it sounds.

    Btw will you be using two bridge rectifiers per side?

    On the back plate I'd like to keep iec and speaker outputs at the bottom, inputs and on/off switch on top (which is easier to reach with the hand when standing in front).
     
  8. Mynamemynaim

    Mynamemynaim 38yrs a Naim owner

    I have to position inputs / outputs very carefully ....as I have one of those stupidly designed Naim Fraim stands:eek:

    It doesn't even suit a lot of Naim gear!
    How useful is that?
     
  9. Mike Hanson

    Mike Hanson Lovely!

    I'm going as fast as I can find the time. I finished the back panel yesterday (see pictures below), and will be mounting the NCC300 modules on the heatsinks next. If I can get that done today, then I may start adding components to the base mounting plate.

    I hadn't planned on it. What's the benefit?

    That switch is not to turn it on. It's to toggle between the IEC and PowerCON power connectors. There will be a separate latching pushbutton switch (with LED) in the front panel.

    Here's the back panel work from yesterday. With this particular enclosure, I decided to try using the pre-drilled mounting plate, so I decided that I could go with the cheaper steel panels rather than the 3mm aluminum that I usually use. It drills fine, but the jigsaw makes a mess of the square holes. (That's another reason why I like the Neutrik connectors, as they can be done really cleanly and consistently with a punch.)

    The extra four holes on each side are to mount the speaker protection module.

    [​IMG]

    [​IMG]

    [​IMG]
     
  10. Mike Hanson

    Mike Hanson Lovely!

    I'm still using Mana racks. My only beef with them is that the shelf height is a bit tight. Otherwise, they're doing their job.
     
    Mynamemynaim likes this.
  11. 337alant

    337alant Negatively Biased

    I also use 470uf F&T axial caps on my NCC-300 build + a 1uf Poly Propylene, would be interesting to know the difference betwen the 47uf + Mil spec solid tant LesW uses ?
    F&T Electrolytic Axial Type A Capacitors | HIFICollective
    I chose the 470uf based on Martin Clarks experiment on output transistor local decoupling with Naim Nait
    Modifying Naim Audio power amplifiers (acoustica.org.uk)
    Have to say I am very happy with my NCC300 amps as is, they are effortless and transparent

    Alan
     
    OldSkool likes this.
  12. Gervais Cote

    Gervais Cote Predator

    These recessed RCA connectors are lovely. Probably makes it more robust as well.
     
  13. geoturbo

    geoturbo pfm Member

    Well done Mike.
    As for the bridges, one bridge per side is usually employed with a centre tap transformer, but two bridges per side would be better in order preferably not to have the transformer directly connected to the ground, as far as I understand you would like to ground the psu after the filter capacitors.
    My 5cs above.. I'd call Les for a doublecheck and or wait for a more experienced user to confirm the way to go.
     
  14. Mike Hanson

    Mike Hanson Lovely!

    I'm curious about this, so I'll do a bit more research. The transformers I'm using are 2 x 40V, which I stack to get 40-0-40, for a quasi-CT. FYI, I've decided to go with the single pair of PS caps for each channel, so there's no such thing as "after the filter capacitors".
     
  15. Mike Hanson

    Mike Hanson Lovely!

    I got the NCC300 boards mounted to the heatsinks yesterday, so it's starting to look like something.

    [​IMG]

    I've got a few holes to drill in the mounting plate for the transformers, SSM, and bridge rectifiers. I don't usually use the inner baseplate from Modushop, choosing instead to drill holes directly in the aluminum base plate of the enclosure. Given the spare vertical height of this enclosure, I decided to try it out.
    • The plate has holes every 1cm. One might think this makes things easier, but ironically not. None of the boards' mounting holes align with this 1cm grid, so I still have to drill three out of four holes. Even worse, some "almost" line up, and I cannot drill near an existing hole. Consequently, I'm having to drill four holes for each board. The base is steel, which is much harder to drill than aluminum.
    • The transformer bolts need a bigger hole, so I have to drill that out anyway.
    • At least my capacitor mounting brackets line up, and use screws small enough to fit through the existing holes.
    • I realized last night that I can't just drop the "circle" (as shown in the image above) onto the mounting plate. The plate sits on top of the bottom steel corner brackets, so I must remove the bottom screws (one side at a time) to maneuver the plate into position. I don't want to do this with the very heavy transformers attached, so I'll have to slip them into place later.
    • At least the mounting hardware will be hidden inside, keeping the bottom of my case unmarred. Of course, you only see that once.
    In conclusion, I'm not a big fan of the mounting plate.
     
    Last edited: Oct 25, 2021
  16. Mike Hanson

    Mike Hanson Lovely!

    I've done some more reading, and I see how two bridges would be necessary if I had two transformers. In this case it's dual secondary windings of the same transformer. If I connect them properly, the joined leads should appear as a correct centre tap. At least that's how many of my amps have been configured, using transformers like this one, for which I connect red and orange to create a virtual CT.
     
    Last edited: Oct 25, 2021
  17. Gervais Cote

    Gervais Cote Predator

    I didn’t realize the whole side wall was a heat sink so forget what I told you about the vertical mounting of the boards, they won’t suffer from heat and surrounding parts will stay cold or worse case slightly warm so not a concern.
    This looks more like an enclosure for a class A amplifier but gives a huge safety factor for an A/B amp so good to go.
     
    Mike Hanson likes this.
  18. Mynamemynaim

    Mynamemynaim 38yrs a Naim owner

    I wasn't a big fan of the modushop cases base either...but on balance...the extra strength and the lack of holes needed in the aluminium base make it worth it
    The main problem I found with them was the need to bend the base to get the case sides to line up properly
     
  19. Mike Hanson

    Mike Hanson Lovely!

    Most of the parts are in (except for the speaker protection modules on the back panel, because I have to solder a couple of spades connectors to the board). I'll likely have that together later this week, so that I can start wiring and testing this weekend.

    [​IMG]
     
  20. Mike Hanson

    Mike Hanson Lovely!

    I suspect I know what's going on. Most of Modushop's parts are symmetrical, so that left/right, top/bottom, and front/back doesn't matter. However, I've found the top and bottom 3mm aluminum panels break this pattern. You need to get them oriented correctly for the holes to line up properly. Get it wrong, and it's a real pain to get the screws in, but it is possible, so you don't necessarily realize it's wrong. Flip the panel front to back, and it's much easier.

    For that matter, the top and bottom panels of the steel enclosures are also oriented with a specific front and back orientation: The flange goes all the way across the back, but stops short of the corners in the front.

    Additionally, I find it best to get all the screws in loosely, before tightening things down. For example, I started with my steel brackets tightened down to the side heatsinks. Then I couldn't get the screws lined up to connect the front panel. I loosened the screws on the heatsinks, and suddenly everything went together really well.
     

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