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ALWSR Build Thread

Discussion in 'd.i.y.' started by timH, Apr 5, 2019.

  1. IDM

    IDM pfm Member

    Yes it is right. I just built a negative one and it works.

    The way I worked it out was to look at the orientation of C3 which is across the opamp supply lines, pin4 being -ve and pin7 being +ve.

    Cheers
    Ian
     
  2. Tom Bonjour

    Tom Bonjour Member

    The AD825 does not appear to be available and/or just not a stock item here in the USA. Would the AD825ARZ be an appropriate device?
     
  3. timH

    timH Senior Moment Member

    Hope so because that’s what I’ve used :)
     
  4. geoturbo

    geoturbo Well-Known Member

    I am one of those awaiting for most hints related to parts to be considered for these boards.. while awaiting - being not sure if this request should be in the ALWSR Build Thread or on its own, mods feel free to move - I routed 32-5 signal to amps directly, and as Snaic5 2x audio wires are free.. I am wondering if 4x regulators could be fixed into a Naim Snaps psu.. anyone has put 4x ALWSR into a Snaps?
    Maybe more than someone will advice to leave the 2x 24v standard rails and put 4x ALWSR into the 32-5 closer to the boards (without 27ohm resistors), and the next will be hopefully a valid and more general question to this build thread..
    What would be best way to properly install these boards into a preamp or other diy project? Are some stands/heatsinks available to be glue melted in place so that boards are fixed safely into the various electronics?
    Any hints and speaking pictures will be welcome!
    Cheers,
    Matt.
     
  5. timH

    timH Senior Moment Member

    Andy has a manual for modifying a SNAPS here
    But if you can find the space it may well be better to fit 4 regs in the 32.5 case. I'm sure super-regging the snaps will be a major improvement if you can't.
     
    Last edited: Apr 17, 2019
  6. timH

    timH Senior Moment Member

    Being a fully paid up member of the Bloody Idiots Club I went and wired up a Negative Reg a**e about face. So I thought I'd do a piccy - just in case ;)

    [​IMG]
     
  7. Tom Bonjour

    Tom Bonjour Member

    The LM329DZ is listed as obsolete and out of stock with the vendors I have checked here in the United States. I found that an eBay seller has a stock of National Semiconductor LM329DZ's which are being sold for $9.95 for each lot of 5. It appears that they have 25 lots remaining.
     
  8. Shadders

    Shadders pfm Member

    Hi,
    If you check Mouser, then they have an equivalent :

    https://www.mouser.co.uk/ProductDetail/Analog-Devices/LM329AZPBF?qs=sGAEpiMZZMuBck1X%2B7j9fHFSdgSLjTHns3EU3J9jraQ=

    It has 10ppm/degC temperature coefficient. I ordered other products this week from Mouser UK and they ship from the US - so i think you could obtain them easily. There is a 20ppm/degC part also :

    https://www.mouser.co.uk/ProductDetail/Analog-Devices/LM329BZPBF?qs=sGAEpiMZZMuBck1X%2B7j9fHFSdgSLjTHnhjbn9%2BnrsJA=

    I would never purchase electronic components from ebay, since there is no guarantee of them not being counterfeit goods. They may function, but they may also have serious performance issues.

    Regards,
    Shadders.
     
  9. martin clark

    martin clark pinko bodger

    While the LM329 is attractive in that it has a very-low dynamic impedance makes for inherent excellent ripple rejection - the output from it (the voltage reference) is low-pass filtered anyway.

    So you can use any two-terminal voltage reference that is convenient - from a string of LEDs (3 x cheap green LEDs will yield c.5.85v; 4 x cheap red LEDs in series about 6.5v; both these ideas are intrinsically exceptionally-quiet ) - to any alternative proprietary voltage reference parts, or a zener diode (yes really - just make sure the series resistor is picked to run some decent current through it, 5-10mA*). All you need to do is calculate the feedback divider to get your target output voltage :)


    *nb this is actually a good choice if you are looking for higher output voltages from your super-regs, 24vDC or more - run a higher-voltage reference, and therefore less closed-loop gain - which wraps-in more feedback. A 12-15v zener run at such a decent current is quiet - noise in the uV range.
     
  10. Andrew L Weekes

    Andrew L Weekes Senior Reverse Engineer

    Yep, that's fine, and what I should put on the BOM.

    Will try and do some updates today.
     
  11. Andrew L Weekes

    Andrew L Weekes Senior Reverse Engineer

    Analog Devices still list the part as current production, it just seems fewer distributors offer the ADi part. Martin's advice above is (as always) very good and there are alternatives you can try. We used the LED reference idea in the PFM Flea and from memory that was pretty thermally stable and very quiet.

    I don't know if they are still as generous, but ADi used to be great for free sample requests...
     
  12. john.luckins

    john.luckins pfm Member

    Here's another idea. How about replacing R3, the lower arm resistor in the tracking pre-reg 317/337 with an led. Makes for lower noise from the pre-reg and slightly more voltage headroom is needed for the entire reg (about 0.5 volts more). I've tried it a few times and liked what I have heard. You don't need the additional cap across R3 and the LED gives similar benefits.

    I've always kept the tracking pre regs in place and where possible preceded the entire reg with a Cap multiplier. best of both worlds IMHO.
     
  13. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    TL431 makes good adjustable voltage ref;) RC filter output as desired...
     
  14. john.luckins

    john.luckins pfm Member

    Also good for the 5v reg as it goes down to 2.5 volts.
     
  15. timH

    timH Senior Moment Member

    Couldn’t you use just one green led for the voltage ref on the 5v (and lower) versions
     
  16. timH

    timH Senior Moment Member

    I’ve got two each of the 329az, bz and cz plus two ad825arz on the way - just waiting for them to confirm delivery. In the meantime Cricklewood have the dz versions for £2.25 + vat
     
  17. john.luckins

    john.luckins pfm Member

    Yes you could and I have but performance will depend upon the common mode input voltage range of the opamp in use. If the opamp is running off voltage rails of 5v and 0v then it is best to keep the input voltage as close to mid rail as possible. It also makes the calculation of the feedback resistors a doddle. 1k each. Walter Jungs GLED is an even quieter reference at near 2.5volts. One resistor, one green LED and a particularly quiet PNP. Worth a google.

    Also an LED has a higher dynamic impedance than a TL431 10's of ohms vs less than an ohm, and with only a resistor feeding it with a milliamp or more you will not get the low frequency rejection from an LED that you do from a TL431 or even the GLED. Without that rejection there is a real danger of low frequency load variant signal getting from the output rail back into the opamp feedback loop. IMHO that is more destructive of output quality than the additional noise of a TL431.
     
  18. midcm1

    midcm1 pfm Member

    Hi All. I'm ditching 4 super regs and 2 more I re did the pcb. I'll post on the Classified section. All were working, although one had a dimmer LED, never got to the bottom of why. May be useful for parts or if anyone wants to use.
     
  19. IDM

    IDM pfm Member

    I just built a -5V reg using the old manual for guidance so:
    AD817
    TL431
    R5 =249R
    R8 =1k
    R9 =1K
    D2 = 1N5333B

    But on test I only get 2.64V out.

    This is the first ALWSR I have built that hasn't produced the expected output voltage. Any ideas please?

    Cheers
    Ian
     
  20. timH

    timH Senior Moment Member

    2.64v might possibly be what you’re getting across the pre reg - easily checked. If so that would mean the SReg isn’t working. Not sure where to go after that but it’s a start.
     

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