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Courtiestown - Naim Amplifier (Avondale) Upgrade Project

Discussion in 'd.i.y.' started by Richard Lines, Dec 7, 2021.

  1. Richard Lines

    Richard Lines pfm Member

    Good Afternoon All,

    OK so the Isobarik project is currently on hold pending the arrival of another pair of TDL 3021/ GT01 bass drivers. I see there are two pairs of TDL Studio 4's up for sale on a well known internet auction site currently but paying £800 or £940 just to prise two bass drivers out seems a bit OTT.

    Next up is doing something with the 6off Naim amplifiers. I am not going to be doing anything out of the ordinary and will be fitting the well established Avondale units as many have done before me.

    I plan on doing this one amplifier at a time as funds permit. I have ordered a pair of HCR200 regulator boards, an SSM2 and a MiniCap 6 off Les and have just bought a pair of NCC200's being sold on here. I will also be fitting a Velleman 4700 speaker protection unit thingy.

    I was intrigued to note the tantalum capacitor fitted to the boards I've just bought, I thought hang on they look an awful lot like the ones we sell, or at least did;

    [​IMG]

    A quick check of my records reveal I sold these to Mark back in January 2012............. I still have a number of them lying around here............

    I have the one NAP250 which has never been serviced so far as I'm aware which will be the recipient of these parts.

    Regards

    Richard
     
  2. Mike Hanson

    Mike Hanson Lovely!

    That's should be a fairly straightforward build, Richard. If you have any questions, we'll be watching and ready to guide you. :)
     
    Richard Lines likes this.
  3. GWM

    GWM Lost in the 70's

    That 47uF is a bit on the low side , 100uF or more gives a better bass performance, the caps I got from Les were 120uF for this position, I think Naim use to parallel parts here on the 250.
     
    chiily likes this.
  4. MJS

    MJS Technical Tinkerer

    Cut off frequency at 3 and a bit Hz instead of 1.6, I've used 47uF film caps in the feedback and there's really no less bass. The type of cap more than makes up for it.
     
  5. Richard Lines

    Richard Lines pfm Member

    Good Evening All,

    As I'm stuck on this ship off France not doing a great deal (truth be told - lots of wx downtime) I've been working my way back through all the past D.I.Y. pages and am now back to p.131.

    Regarding the 47uF, yes I've seen a photo of a board with a 82uF and another with a 47uF soldered both sides. I've dozens of 47uF/ 50V tantalums so that's not an issue.

    I've learnt that there was a v1.5 of the PCB with a NCC220 type TR5 BD237 heatsink option, Teddy Pardo's VBE multiplier, paralleling output transistors so a bit to go at.

    I'll likely be firing questions off to some lucky people.

    I can't see any components that aren't available somewhere BC128's and BUV20's are out there, some priced more than I'd like to pay but they're available.......

    I'll be putting out requests for UBG NCC200 PCB's next................

    Regards

    Richard
     
  6. Richard Lines

    Richard Lines pfm Member

    Good Evening,

    That's me just read the VBE thread so I could be on the lookout for VBE PCB's now.......

    Regards

    Richard
     
  7. GWM

    GWM Lost in the 70's

    I have a pair of part built VBE's but your never going to be able to fit them in a 250 case together with the extra power supply unless you make into a mono.
     
  8. Richard Lines

    Richard Lines pfm Member

    Good Evening GWM (and others),

    Yes it certainly looks that way. The MiniCap6 looks like it would sit on its long side and still fit the casework (?????) but I don't know as that would help. I still need to find room for the transformer to supply a VBE - do I need two?

    There is that VBE modification that Teddy Pardo came up with to consider as well.

    The simplest option would be to go the NCC220 route but what is the fun in that - I don't mind a challenge.

    As I have 6 boxes already I certainly don't want to add to that but having said that I will have gotten rid of 2 x Supercap, 1 x NAC52 and a SNAXO 3-6 and only added an Exactbox.

    Empty Naim enclosures are a bit thin on the ground................................

    Regards

    Richard
     
  9. GWM

    GWM Lost in the 70's

    If you are considering converting the 250 into a voyager configuration where the front end of the NCC200 is supplied from a vibe and outlet directly from the smoothing caps with the existing NAIM transformer then you need to check the voltages.Les suggests 50V is optimum I have 53/54 on mine which is probably borderline but hasn't been a problem for many years of use.Can't remember what the voltage into the Naim reg is but it may be to high.
     
  10. Mike Hanson

    Mike Hanson Lovely!

    One VBE typically power one amp module's input stage. That VBE needs a 50-0-50VAC transformer (or thereabouts).

    Given the low current requirements of the input stage, I've considered using a single VBE to power the input stage of two amp modules, but you have to watch out for issues like ground loops. I've not actually done this yet. and it may not really work. Therefore, you really should plan for a separate VBE per amp board. This all assumes you want to build your amp with a Voyager configuration (regulated power for the isolated input stage, instead of borrowing input stage power from the output stage).

    The alternative is to use regulated power for the entire amp module, in which case you'll want to use a single HRC200 per NCC200, and ignore VBE's entirely. This works well, because you can feed both boards with a single transformer and MiniCap6. All that will fit into a single Naim NAP250 case (which is essentially the same overall topology as a Naim NAP250). You can squeeze an SSM in there too, but you won't likely manage a speaker protection module.

    If you want a dual-mono amp with regulators, you won't fit it into a NAP250 case.
     
  11. Richard Lines

    Richard Lines pfm Member

    Good Evening All,

    Phoned Avondale this morning and spoke to Gavin to get a "sense check". I've ordered NCC200 "kits" from them.

    Stuff arrived today in the shape of what will be to your guys familiar stuff;

    [​IMG]

    [​IMG]

    [​IMG]

    I do wonder what people define as unobtainium;

    [​IMG]

    OK so I haven't found any 10uF/ 25V BC128's as yet but have found some 3.3uF's so will likely have to parallel 3 of them. It is always a challenge trying to work out how some sellers describe what they're selling and that includes spelling errors.

    The BUV20's are "en route" as well - believed genuine - certainly not sourced from anywhere near the Far East.

    Spent a large part of this afternoon trying to source parts to build a couple of boards, I now have some sympathy for businesses. Surprising shortages and some lead times running out to 10 months. Found the parts between RS, Farnell and Mouser.

    Next up looking to suitable cabling for connecting it all together - what are others using?

    Regards

    Richard
     
  12. Mike Hanson

    Mike Hanson Lovely!

    It's just like Christmas, eh? :D

    As for wiring, I've been using silver-plated multi-strand with PTFE insultation for anything that carries signal. I usually get my via eBay. I'm not so picky on the power side. For the input signal, I use twisted 22AWG for short runs away from EMI. If it's a long run and/or near EMI, I use Cardas 1x21.5 Coax, but that stuff is a hassle (solder pot, etc.).
     
  13. Richard Lines

    Richard Lines pfm Member

    Good Evening All (again),

    You do need to be wary out there in internet land. I could be generous and believe that people think SEL is the same as SAL but they aren't. SAL is clearly Solid Aluminium whereas it looks like SEL will be solid but very likely tantalum.

    As this picture shows they're not even the same shape;

    [​IMG]

    SEL on the left and the genuine article on the right..........

    I am struggling to find 10uF/ 25V though.........

    Regards

    Richard
     
  14. chiily

    chiily PFM Special Builder

    Richard, how many BC128s do you need @10uF?
     
  15. martin clark

    martin clark pinko bodger

    I would suggest - this is not a difference to get remotely excited about: certainly not from the POV of limits upon this amp architecture performance; in fact -far from it.

    Enjoy the build.
     
    Mike Hanson likes this.
  16. Richard Lines

    Richard Lines pfm Member

    Martin - I am simply trying to emulate the work done before me, arm myself with the same devices and come to my own conclusions. The "correct" device for C6 seems to be a particular case in point. I'm certainly not going to try and re-invent the wheel.

    Regards

    Richard
     
  17. Richard Lines

    Richard Lines pfm Member

    I've bought 10 NCC200 v1.5 boards off Avondale to change out all my amplifiers so, in a perfect world, 10 please, but anything would be a start. Worst case is I parallel up 3.3 or 4.7uF versions.

    Regards

    Richard
     
  18. 337alant

    337alant Negatively Biased

    LesW also used the EVOX MMK film caps for the 10uf input cap and they are readily available form RS
    MMK22.5106J63D15L4TRAY | KEMET MMK Polyester Film Capacitor, 40 V ac, 63 V dc, ±5%, 10μF, Through Hole | RS Components (rs-online.com)
    2PCS EVOX MMK BW2 10UF 100V capacitor | eBay
    MMK15225J63B05L4BULK | KEMET MMK Polyester Film Capacitor, 40 V ac, 63 V dc, ±5%, 2.2μF, Through Hole | RS Components (rs-online.com)
    The 68uf BC128 are ideal for the bypass cap on TR5
    For the feed back Cap C6 the best cap IMHO is a Wet Tantalum brass case Mil Spec

    Alan
     
  19. Richard Lines

    Richard Lines pfm Member

    Good Morning All,

    I've ordered a set of bits although it did take a while as the original BOM has some part numbers which Farnell are either no longer supplying or are on various amounts of back order delay.

    I've saved it here (time to see if I can make this work!!!) - https://docs.google.com/spreadsheet...ouid=104404634061394323084&rtpof=true&sd=true

    Good grief it works and there is still some space on our Google drive that Kate hasn't filled with horsey video's................

    Regards

    Richard
     
  20. GWM

    GWM Lost in the 70's

    I wouldn't worry to much about those caps, the feedback one has the biggest influence and as long as their axial tants above 100uF your ok, Les uses films for inlet and that's what I use but tried allsorts and its small differences, the 68uF across the bias transistor has very little influence I have a 47uF axial tant just like the one you have in feedback and that works great, think Les uses tant beads here now just like Naim.
     

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