official GDIY51PSU Help & Support Thread

[jsteiger]

Yes, thanks for that link Harpo. Very interesting indeed. Just from reading that article, it appears to make sense to use the snubber caps. I was gonna ask if you did calculate them Volker. I know some of this work was done on the secret German Forum.

I thought I remembered something about JDBakker not wanting them. I don't recall why though.

Thanks guys,
Jeff

 

[zayance]

Yes, thanks for that link Harpo. Very interesting indeed. Just from reading that article, it appears to make sense to use the snubber caps. I was gonna ask if you did calculate them Volker. I know some of this work was done on the secret German Forum.

I thought I remembered something about JDBakker not wanting them. I don't recall why though.

Thanks guys,
Jeff

Svart was talking about it in this discussion:

http://www.groupdiy.com/index.php?topic=27819.0

 

[[silent:arts]]

... I was gonna ask if you did calculate them Volker. I know some of this work was done on the secret German Forum ...

Harpo gave me a helping hand calculating the +/-1V trimmer window,
and changed some other resistor values to be safe with half watt resistors.
thanks again for this!
But this happened very old fashioned, we used email, no forums ;D ;D ;D

I'm only a PCB designer. neither a maths nor an electronica vizard.

at the moment I'm trying to talk Harpo into designing the 51X audiophile high end PSU,
with all options he wants to have  

 

[jdbakker]

Some reading here on snubbers http://www.hagtech.com/pdf/snubber.pdf

Interesting paper, albeit a bit heavy on the theoretical side. Thanks.

I thought I remembered something about JDBakker not wanting them. I don't recall why though.

As mentioned in the paper (and by Svart in the thread zayance linked to): just putting capacitors in parallel with the diodes does nothing to dampen the ringing, it just shifts its frequency. Depending on the EMI/RFI susceptibility of the rest of the circuit this may help or hurt the impact on audio-band performance. To properly dampen the ringing you need a pole-zero network -> a resistor in series with the capacitor.

However, I would argue that with modern components there are better ways to address the problem at the source. Diodes with faster turn-off help a lot; while in '95 when the abovementioned paper was written these were still somewhat "exotic", the rise of SMPSes and PFCs have produced a large selection of affordable Schottky and SiC diodes. Any residual ringing can then be addressed by a zobel/snubber across the secondary winding of the power transformer. We've had a discussion on zobel/snubber design for power transformers but I can't seem to find it ATM.

JDB.
[for those wanting to experiment with SiC rectifiers: keep in mind that most have a lower absolute maximum non-repetitive peak current rating than regular or Schottky diodes, so make sure the ESR of the post-rectifier buffer cap isn't too low]

 

[[silent:arts]]

thanks JDB.

can't either find the discussions, but would like to read them again.

however, with this particular PSU I don't see any problems with either leaving them in nor out.
as said before, an option you decide on your own

 

[jdbakker]

can't either find the discussions, but would like to read them again.

I think I was thinking of this post by Steve Hogan (item 3 on his list). Also relevant wrt caps across diodes is this post by bcarso.

JD 'to snub or not to snub' B.

 

[grantlack]

Hi All

I built a supply with 2 PSU boards ready for the next rack. The supply has fuses on each rail rated for the regulators. We loaded the rack with 4 VP25, 2 X-12MK500, 2 API512, 3 API 550b. Then ran white noise signal though all and had no heat issues. My heat sink is a 2x2x1/8 aluminum angle running the length of the board then bolted to the steel case. The fuse's are cheap insurance against my bad Diy projects, hot swap mishaps and you can take your eye off the ammeter.

JamesW

Hi James, you are not alone ;D
my personnel will include two PSUs too ;D
and I know of a few others ...

SHOW US PICS

are you going with a toroid per board, or just current dividing by wiring the boards in parallel with a beefier transformer?  i've got 2 almost completed racks (and still need a third), a nose full of rosin fumes, and an itch for some power supply action  ;D.  by the way, thanks jeff!

EDIT: thanks to all three of you, jeff just happens to get bonus points for his insane packing job.  marines don't make a bunk that tidy!

 

[[silent:arts]]

... are you going with a toroid per board, or just current dividing by wiring the boards in parallel with a beefier transformer?...

I am using a toroid for each board

 

[johnnyscotch]

Hey guys,
2 questions:

I might have missed this in the thread, but does anyone have a specific torroid suggestion for a fella who doesn't need the +-24v??

and,
You either ground with the "ground" or "chassis", correct? Not both......
For instance, I'm using the shield lead on my amphenol connector cable for "chassis". I wired up another lead for ground, but I didn't plan on connecting it to anything......Will this work?

cheers

 

[sahib]

You need two seperate transfromers. 2x18V @ 2-3A  will be good for 16V supply and 2x24V secondary @ 250mA for the 48V supply.

In terms of your ground connection you are fine. Shield provides safety ground connection between the psu and 511 chassis'. However, if you have unbalanced input in any of your modules and encounter radio interference then you can connect a few picofarad cap between the circuit ground and chassis/safety ground right at the input connector. But you do that only when you need it. Otherwise if ain't broke no need to fix it.

 

[johnnyscotch]

Has anyone built this with an off-the-shelf torroid??

If so, I'll give you a buffalo nickel for a part number, I can't find anything........ ??? ???

 

[jsteiger]

Just in case anyone is in the need, I discovered Redco has male and female 7 pin Neutrik XLR connectors. Both panel mount and cable mount.

Redco 7 pin XLR's

Cheers, Jeff

 

[Ptownkid]

However...keep in mind that the plate mount ones won't fit without some hole enlarging.

 

[jsteiger]

Hi Volker,

A small observation. As the LM350's were changed to LM317's, the schematic and parts overlay in the 1st post still show LM350. Might confuse a beginner? (Or a simpleton like me :)

BTW, It's been a fun build so far. I have decided not to use the ceramics. Most all PSU schemo's these days do not appear to use them, FWIW.

Best, Jeff

 

[Denyle Guitars]

Just in case anyone is in the need, I discovered Redco has male and female 7 pin Neutrik XLR connectors. Both panel mount and cable mount.

Redco 7 pin XLR's

Cheers, Jeff

That's what I'm using. Bought them from Chris a while back since I needed some wire for another project.

Fitment of the D series panel jacks is a bit tricky, fwiw. Plan to bust out the Dremel. 

 

[stereokillah]

hi,
i feel my question stupid but, why i've the god vaotage and all my led 3mm don't be illuminated?
no one led is working, i tried withh red white yellow, around 2volts wich resistor work with it perhaps it's stronger for mine.

 

[jsteiger]

Your LED's are probably in backwards maybe? Try flipping the leads around.

 

[stereokillah]

i said stupid no? it is!

thank you so, i'm tired i thought the square on borad for the +.
now it's working.

 

[johnnyscotch]

nevermind.....I'm an idiot....

 

[johnnyscotch]

Jeff,

I decided to go with the proper transformer so I can run the 24v as well. What is the lead time on the ones you're ordering? I need this up and running in May, and I just wonder if I should buy a custom one or not.

cheers