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Neil mcbrides pre-amp regs

Discussion in 'd.i.y.' started by fatmarley, Mar 28, 2004.

  1. fatmarley

    fatmarley Registered User

  2. Jo Sharp

    Jo Sharp Pulls on doors marked push

    The LT1086 CTs may not need heatsinking - depends on the voltage drop. The LM329CZs are good and will not need heatsinks.

    The type of resistor does not matter much - 0.5 watt will do fine.

    Worth experimenting with different capacitor types on the output: bigger value than 10uF might be better - and try OSCONs, SILMICs or Black Gates.

    I found Press-N-Peel to be very good for making small PCBs in small quantities. Suggest you prepare as many as you can fit onto one sheet of blank PCB; this will give you extra boards if you decide to multi-reg (and I suspect you will).

    Good luck
  3. RichardH

    RichardH Bodging pleb

    No need for heat sink compound, I'd say - the clip on 'sinks will mate well enough for this purpose without.

    The LM329CZs are TO92 format - i.e. like the transistors on Naim preamp boards, so no heatsink needed there!
  4. pm1961

    pm1961 pfm Member

    Here are exactly the regs you are considering laid out on strip board.

    Admittedly it does not look as "professional" as a PCB but it is compact, quick and cheap.

    FWIW, you are looking at two regs on one board to power the line stages and one each tagged onto the phono cards. The buffer stage and balance control have both been bypassed.

    Any questions just ask.... I'm no expert but its amazing what you pick up along the way when you get your hands dirty!

  5. Mus

    Mus pfm Member

    A nice looking job nonetheless.

    I was wondering why you powered the line stages via a resistor when Neil M recommends removing the resistor? Did you find it sounded better with the resistor in place?


  6. pm1961

    pm1961 pfm Member

    Hi Mus,

    1. I read on other threads that it may be advantageous to leave it in.............. (ALW amongst others...... (I think??)..waiting to be flamed!!!) Together with the associated cap, it forms a filter circuit keeping any residual nasties out I'm led to believe.

    2. It made an easy connection without having to access the underside of the board!!! Probably the main reason if I'm honest!

    I haven't compared it to "without" the 27R so I can't comment. I've been enjoying it too much to dissassemble everything again.

    Although, having now thought about it, it would be relatively simple to re-solder the connection downstream of the 27R whilst leaving it in place.

    I've always been a bit wary of some of the prose used to describe the differences....... "night and day" " beats amps at 10 times the price" and all that, but even a sceptic like me could hear the difference.

    I'm not a great wordsmith but I did find that I could listen at much lower volume levels than I could before and still enjoy it. More experienced people than me say that is down to better separation and reduced noise levels generally........

    There we go...... more to the point........ I can tell the difference.... I enjoyed doing it...... and I'm enthused to go on and do other things................

    When is this Government going to bring in a 48 hour day so that we can get on and do all these projects?:D
  7. Mus

    Mus pfm Member

    "There we go...... more to the point........ I can tell the difference.... I enjoyed doing it...... and I'm enthused to go on and do other things................"

    And that's what its all about, well done :D


  8. fatmarley

    fatmarley Registered User

  9. RichardH

    RichardH Bodging pleb

    Multimeter - Argos (of all places) do one for £24.99 with transistor and capacitor measurement etc. Prod code 701/5603.

    It's an OEM thing - I have the Rapid Electonics version of the same thing (but without temperature measurement). Not sure if you wanted to spend that much, but mine replaced a cheap and crappy one, and I've been really pleased. I also got a set of leads with croc clip ends, which are handy. If you go to CPC or Rapid, then you can also pick yourslef up some reasonable quality and dirt cheap tools if needed - side cutters for snipping component legs, long nose pliers, "helping hands" etc.
  10. pm1961

    pm1961 pfm Member

    Fat Mat,

    Hope this explains.................

    Also, on this you can see the bypass wires for the buffer stage and the links replacing the balance control. Filling the hole left by the balance control is a headphone socket.



  11. Mus

    Mus pfm Member

    Check out Maplin they have a nice looking one on special going for £9.99 reduced from £24.99 if I remember right.

    N35AJ M92A Multimeter £9.99

    I am awaiting delivery :)
  12. Linnik

    Linnik Flat Earth - Source First

    Thanks for your splendid photos PM!

    Can you feed headphones directly from the NAC62 output?

    Is it possible to have any drawings on your breadboard connections or if you have a photo taken from stomach side?
    Tried to make one trial on breadboard but it became four times begger at least compared to yours.

    Please show how you made it so neat!!


  13. pm1961

    pm1961 pfm Member

    Hi Oz,

    The line stage drives my Sennheiser HD600 to respectable levels.

    I did replace the balance control with links instead of resistors though because I didn't want to attenuate the signal any further than necessary.

    It sounds mighty fine to me, but then again I have nothing to compare it with..........

    I haven't got a rump shot of the regs but these may help.......
    [​IMG] [​IMG]

    I just took McBrides circuit and sat down with a spotty piece of paper and played around until all the bits joined up correctly.

    From memory, the four vertical tracks from left to right are;
    1. Ground
    2. Voltage adjust
    3. Voltage out
    4. Voltage in.

    The rest of the components should be self evident. Of the bead tants, the larger is 10uf and the two smaller are 1uf. Better caps might show an improvement? I think the trick to keeping it compact was to mount the resistors vertically and to break one of the tracks at key points to incorporate the zenner.

    I did make one where everything was soldered to either the legs of the 1086 or to the relevant component........ short tracks but an abomination to look at!!!!

    If i get a moment, I'll try and sketch something........

  14. Linnik

    Linnik Flat Earth - Source First

    Thanks PM,

    I also passed the bal pot. It is still in place however.

    The volume gets up too early so I have been thinkin the Welwyn resistors here. But if thinkin of the headphones, then of course it would not be good idea to cut the level by additional resistors.

    Thanks for the rail description. I have to think it over on paper. I have just planned to start burning boards for it. Never done that before...

    However I may do that as I have refined NMcB's board for a big series of, was it, 12 second regs on the same board.

    Hehe. Thinkin to feed every single transistor.. :D
    MC cards are away already as I made the prefix.

    But if I decide to get less ambitious I might make it your way after all.

  15. fatmarley

    fatmarley Registered User

  16. Linnik

    Linnik Flat Earth - Source First


    How did you end up for using two smaller tants there.
    IIRC NMcB suggested all of them to be 10 uF ??

  17. pm1961

    pm1961 pfm Member

  18. Linnik

    Linnik Flat Earth - Source First

    Thanks PM.

    I had it taken from the same page but from the
    Dual stage regulators what goes where, in: PDF

    There all the tants are 10 uF. But obviously there is
    not so much difference which one you use.

  19. pm1961

    pm1961 pfm Member

    I don't claim this to be the definitive layout, but it works and it is small......... Don't forget the basic grid is 1/10" or 2.5mm squares!


    In practice I think I left a bit more space between components, but not much more..............

    The biggest problem I had was bridging tracks with solder, so caution advised and check carefully with your meter before applying power.

    Hope this helps..................


    P.S. looking at it again, you could mirror 4 regs around the same point on a piece of veroboard around 60 x 30mm and have a common star earth point in the middle!
  20. Linnik

    Linnik Flat Earth - Source First

    Very nice PM,

    Thanks a lot!!

    I spent few hours on it last night but
    did not get to solutions this clean.

    You mean the common earth for four regs:
    The star would be one line actually?

    Cheers! :)


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