No Compromise Low Voltage PSU

RobsterD

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Hi

I'm in the process of trying out a couple of kits of regulated PSU for my Apogee MiniDAC,both are DIY

Welborne Labs PS REGHC @ 12vand a Sjotstrom Audio JSR03 @13.8v.Will be using encapsulated toroidal transformers,silver wire(HiFi Collective 1mm)and possibly some medical grade IEC inlet filters.Auto

The transformers can be in series or parallell looking @ 18v on the secondary,would 2x9v in series be better than 18v in parallel or doesn't it matter,obviously the current will double in parallell.

Would there be any advantage in using a medical grade IEC inlet filter looking at a the Schaffner range from RS

The JSR03 requires a smoothing capacitor would a Black Gate be OK here,4700uF 35v was specified,any thoughts.

What I'm trying to acheive is the best PSU for the DAC soanyadvice would be greatly appreciated.

Cheers

Rob

 
E

earl of sodbury

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Never scratch-built PSUs, but modded a fair few.

If you're going to filter the power, look for a single-stage module whose inductance is no more than 1uH - Schaffner do several, choose the one with the greatest current-handling capacity. Originally I found thisessential for amplifiers, but tinkering around with offboard filters it seems best for source electronics as well. You can do better (and cheaper) than Schaffner by building your own from decent components, but of course that needs more space and hassle. All IMHO of course.

Everybody has different preferences/ideas about what makes a good filter cap - were it me I'd look at BHC caps of 10,000uF and 50 or 63 volts, if you find you have a choice just compare ripple current figures. All assumesyou have space for them. And don't bypass them.

Bridge diodes and voltage regulators both offer ample scope for much tweakage, too
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RobsterD

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Thanks Chaps

What a good idea,found a DIY mains filter on Triode-Systems seemed to be popular project on WAD forums

Will be usinga 50VA toroidal @ 18v 1.39A wired in parallel to give 18v @ 2.78A

Got a 10000uf 40v BHC so I'll give that a try

Cheers Rob:^

 

RobsterD

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Thanks for that may need to implement that basic cct as the JSR03 is a DC input circuit

So cct will be mains - filter - transformer - 18Vac - schottky diodes 3.3A 100V( 31DQ10) - 10000uf BHC 40v cap - JSR03 super regulator - 10000uf 40v BHC cap DC output

Does above seem OK before I get my inlaw to do the CAD stuff.

Thanks

Rob

 
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earl of sodbury

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RobsterD wrote:

Thanks for that may need to implement that basic cct as the JSR03 is a DC input circuitSo cct will be mains - filter - transformer - 18Vac - schottky diodes 3.3A 100V( 31DQ10) - 10000uf BHC 40v cap - JSR03 super regulator - 10000uf 40v BHC cap DC output and musical heaven
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Does above seem OK before I get my inlaw to do the CAD stuff.

Thanks

Rob
Not sure you need such a high value cap after the super-reg, indeed not sure you need a cap there at-all...? Otherwise should be damn good.

 

felix

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Indeed, that cap can be small (and therefore high quality). Using a small film cap (3-10uF with a small resistor in series with it (yes, I do mean a film cap+half an ohm connected between +ve out and ground) will be about right - and gets rid of one big elctrolytic cap, with all the vagaries they can bring.

Thi sis cheap, and works better out a lot further into HF than any electrolytic cap can. It will also damp any tendency to ring due to the film caps low ESR , or inductve properties of the cable to the dac and any input cap there.

You might also like to give some thought to the quality of the power interconnection to the DAC. You want this to be low impedance, so shorter will be better from a voltage regulation POV. HTH!

 

RobsterD

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Thanks for your replies,I wasn't sure either on the output cap so didn't buy one(when messing with class T amps someone recommended a 10000uf so I just thought it'll do)

The smoothing cap pre reg will that be fine how do you determine what size,is there an equation ?

Will be doing the cct tom,brother inlaw has a PCB milling machine so should be fun.

Also having read technobears link quite like the idea of caps bypassing the diodes to eliminate switching,trouble is the super reg will be doing all that anyway hopefully,so gotta be careful how far I take the basic cct.

Cheers
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RobsterD

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Hi well its finished and first impressionsseemgood with deeper bass etc.Caps are Mundorf and used a 4700uf on the o/p,I'll let it burn in for awhile before making any real judgements,must admit it was enjoyable making it.

 
E

earl of sodbury

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Very Nice Work sir! You went to town on that baby and no mistake.
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It will benefit from at least a fortnight's run-in.

Really must get my arse in gear and do some scratch-builds!
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churz, eofs

 

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