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The more Reg's the better On Naim 72 ???

Discussion in 'd.i.y.' started by Mynamemynaim, May 18, 2020.

  1. nobeone

    nobeone pfm Member

    Apologies, just the usual case of thread drift, we started discussing extra regulation and the potential benefits of more despite having RSL MagicPower board with integral regulation, Kit's view of regulation is perhaps best represented in thinking about a ZapCap then the RSL pre which had an extra stage of regulation then the MagicPower cards with integral regulation. Obviously a ZapCap is not for someone on the diy path like yourself, however it is a way to hear Kit's view on regulation. A means to an end, try the ZapCap, get a taste of what Kit's regulators can do for you, if you like it then ...

    ... a diy variation on the theme might be a PSM-1 in a Hicap (or PSM-2 in a FlatCap) then a couple or four regulators in the pre feeding the MagicPower cards ...

    ... which might well not appeal to you at all, it does to me, and perhaps to other folk reading this that haven't crafted a nice diy Hicap/ALWSR :)

    I don't believe the Teddy Reg is like an ALWSR.
     
  2. RyanSoundLab

    RyanSoundLab Trade: Ryan Sound Lab

    Responding to a couple of posts above, a third level of regulation is a noticeable, if lesser, improvement than 2 levels. If you're going for the ultimate, then why not? In my case, I designed a new preamp motherboard that included the "middle" regulator level on it so it was very close to the plug-in sound boards (321, etc). All 3 levels utilized Linear Technology LDO IC regulator chips, either LT3080 or LT3082. As I've mentioned elsewhere, it is almost impossible to even match the performance of a modern regulator IC, much less do better than one. If you want to try putting a 3rd level of regulator on a typical Naim system, you will have to keep it small to fit inside a 72 case, for example. The IC fills this role well.

    I wrote a descriptive summary of a few of the existing regulator types on AudioFlat here: http://www.audioflat.co.uk/phpBB3/viewtopic.php?f=7&t=1034&start=60 which might help understanding the differences among them.

    I will also make a potentially controversial comment about "noisy regulators". At the bottom of this linked post on AudioFlat is a brief discussion about noise and how noticeable it is on different types of preamp circuits. In short, you won't get much, if any, noise coming out of your speakers from the preamp power supply on a Naim-type system because of the feedback amplifier circuits it uses. They strongly attenuate any supply noise. In addition, the newer IC regulators produce very little noise, so there's no reason to go for a "ultra low noise" power supply design. Low impedance and good transient performance are more important in my view.
     
    rontoolsie, YNWOAN and chrisn like this.
  3. sq225917

    sq225917 Bit of this, bit of that

    The str hits -100db, the alwsr hits -130db psrr, the alwsr is also lower output impedance. Of course there are other parameters to consider.

    There also Salas's ultra bib 1.3 shunt reg to consider.
     
  4. Mynamemynaim

    Mynamemynaim 35yrs a Naim owner

    Thanks again everyone for your contributions

    Now I'm in a quandary again...but think it may well be an itch I have to scratch now!!

    I'll shut up for now and do some thinking...and collecting of parts..and see were it leads me
     
  5. nuit73

    nuit73 nuit73

    "If you want to try putting a 3rd level of regulator on a typical Naim system, you will have to keep it small to fit inside a 72 case, for example. The IC fills this role well."

    Hello Ryan,
    Thanks very much for all the technical explanation
    You think about what for a small fit in the Naim preamp?
     
  6. RyanSoundLab

    RyanSoundLab Trade: Ryan Sound Lab

    If you can get ahold of Linear Techs (now Analog Devices) LT3080, they come in a TO-220 package with 5 leads. You can work with that fairly easily and use a perfboard for mounting the parts if you want. (You can use another LDO IC if you prefer but don't use an LM317 - it will hurt the sound.)

    You will need 2 IC's, one for each rail. The voltage is set using a single resistor for each - in this case 2.4Megs for 24v. (yes, very high impedance so you need to be sure the board is clean after putting it together to avoid any leakage to ground). You can make it adjustable as shown below if you prefer. The HiCap (or whatever the external supply is) needs to be set about 28v to provide enough headroom. Don't need any heatsink for just the 4v drop with approx 100ma max through each rail (worst case) having only 0.4W disippation. The TO-220 case can handle that by itself. The circuit is very simple (one channel):

    [​IMG]

    I suggest retaining the two Schottky diodes back to back as shown for protecting the IC. C13 can be ceramic or film, C5 needs to be tantalum/35v with a low ESR. R3 is needed to provide a small load for when you don't have any other load attached, otherwise the voltage will drift above the set value.

    You should be able to find some place inside the case to put these. Unsolder the two red rail wires from the motherboard and insert the regulators so you don't have to cut any traces on the motherboard.
     
  7. nuit73

    nuit73 nuit73

    Hello Ryan,
    Very nice...!

    Thanks very much, you are a "switch-on" man !
    I did not think that the LT 3080 was as efficient, it is a component what we do not really know, we all see 317, LT 1083...and all of this serie

    For the two diode , is it possible to have the ref of a non smd type (on a perf board)
    What is the resistor value if i want to up the voltage to 28 volts on the preamp board
     
  8. YNWOAN

    YNWOAN 100% Analogue

    There is a whole thread about my ZapCap experience and subsequent PSM-1 here:

    http://www.audioflat.co.uk/phpBB3/viewtopic.php?f=7&t=1034

    But to paraphrase the whole thing, I think that Kit describes the situation very well when he writes on his own website;

    https://ryansoundlab.com/index.php?...oducts_id=21&zenid=ksum2k0qcuvf9bc165dvfn4n71

    Until very recently I have been a very happy user of the Avondale TPR4 module and my adoption of the RSL PSM-1 has not actually decreased my appreciation of the TPR4 which I still think sounds jolly good.
     
  9. RyanSoundLab

    RyanSoundLab Trade: Ryan Sound Lab

    The Schottky diodes can be almost any rating because it can never get more than 0.3v across it either way. A thru-hole equivalent that I have used is SB160 (Mouser # 512-SB160) rated at 1a and 60v. You can probably use something even lower rated if you have it handy. It's purpose is to protect the adjust pin on the LT1080. For some reason, that can never be allowed to be more than +/- 0.3v different than the output voltage. That aspect of the device seems a bit delicate considering that it is short-circuit proof and thermally protected. Must have been some design limitation.

    You need to download the spec sheet for the LT3080 and read it carefully, just as for any devices you might use. The adjust pin puts out 10ua current and that current goes through a resistor to set the voltage. For example, if you use a 1 Meg resistor from the adjust pin to ground you get 10ua X 1M = 10v. That is the reference for setting the output voltage. If you want 28v out, use 2.8M resistance. Just remember that the maximum input-to-output voltage for the LT3080 is 36v so you can't use it straight from a HiCap reservoir capacitor (which is typically at 39-40v) and still have short-circuit protection. Lots of design trade-offs in every design! It should work fine in the "middle" regulator position you are planning, though.
     
  10. nuit73

    nuit73 nuit73

    Thanks very much for the detail

    Very interested to do this project on a perfboard

    the 2.8M resistance is R11 , I hope, for the 28V output
    For this voltage i have to do an input of 32 volts (of the initial power supply)
     
  11. RyanSoundLab

    RyanSoundLab Trade: Ryan Sound Lab

    Yes, 2.8M is the total resistance from the adjust pin to ground (R11 + R13 in the schematic). 32 volts in will be fine for headroom to 28v out. Good luck on your build!
     
  12. nuit73

    nuit73 nuit73

    Thanks very much for all
    An exciting project!
     
  13. nobeone

    nobeone pfm Member

    Then we just need a little PCB ... :p
     
  14. sq225917

    sq225917 Bit of this, bit of that

    Mmmm. Pcb.....
     

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