Bypassing PS smoothing electro caps

Hey all,

What kind of range should I be looking at when bypassing local PS smoothing electros?? I see the figure 100nF thrown around a bit... can you go smaller than this?? The reason I ask is because I'm ordering bits and pieces for Bauman's N72(have a look at CBP1 etc):

http://www.thediypill.phx.com.br/forumfiles/1272M_REV1.pdf

He's specified 100nF's... but I've got a bunch of 10nF Wimas lying around not doing much!

So is 10nF going to do the trick or should I get some 100nF's?? Or should I just not bother bypassing them at all??

Justin.

You must prefer 100nf caps . 10nf is too small capacitance. If you can find them try bigger capacitance, 150 or 220nf.

If these caps are been in parallel with electrolytics ( it helps electro's high frequency responce ) they must be around 1% the electro's capacitance.

Cheers

Hey Fotis,

Thanks for the reply... I realized I posted a dodgy link (now fixed ). Yes the film caps are in parralel with electrolytics 470u/1000u - from what you're saying I should be looking at even bigger than 150/220nf for these - yes??

Justin.

100nF works fine as a standard value for nearly anything.

Only execption would probably be very-very large electrolytics in power amps, where I'd probably use 1uF's and then some 10nF ceramics as well.

Jakob E.

I remember having read not to bypass the smoothing caps. The small value bypass caps can create a RLC resonance circuit with the ESR and inductance of the big smoothing cap.


Jens

yes, problems can arise from improper thought-out decoupling, but this is a very rare problem indeed.

I think I read it in a book about digital circuits. In this environment things are a little more sensitive (function - no function: the real meaning of digital :green: )

:sam:
Jens

Thanks guys,

Everywhere I'd seen film bypasses mentioned they were 100nF - good to know that figure will stand pretty much anywhere... I was hoping to get away without buying some though... but oh well :grin:

Justin.

You can do an easy test by cranking up a mic pre with no signal and using an alligator clip to ground out a 0.1 uf cap that has the other end on the hot of your B+ voltage, this is an A/B test sequence persuiant to section 8 Part B of the DIY tweakers codebook which states that any and all theories will be verified upon proof of purchase that the involeved parties are legally consequented.

Going to the drugstore as soon as I get paid. Hold on one more day. :?

I'll have what CJ is not having.

go here

http://www.linear.com/search/searchResults.do

look for an13 page 26

I just distilled page 26, uploading now...............

no wait, jpg better, splicing screen capture now...........

no wait, surfing ebay for Traid x-formers better, placing bid now.............

hmm its funny, but 100nF has always got me more trouble than any good when used as PS-"bypass" caps..I have been more lucky with something like 25-47uF...wonder why ???

Kind regards

Peter

:guinness:

http://www.jcmaudio.com/Cap_Bypass_Spliced.jpg

Thanks CJ!

No, Thank You!
:guinness:
Oh yeah, what software to do that?

I used photoshop. you can put the two images on different "layers" and move them around untill you're happy then squash to jpeg. Thanks for posting the info., interesting stuff.
:grin:

100nF works fine as a standard value for nearly anything.

Only execption would probably be very-very large electrolytics in power amps, where I'd probably use 1uF's and then some 10nF ceramics as well.

Click to expand...

I can't remember having seen a film-bypass on the usual big cap in '2/4 discretes+1opamp' mic-pre's (the big cap that's in series with the gain-setting; like for instance in the Green-micpre).
Obviously it needs a very big bypass-cap there then, but most of the times I didn't see anything present, probably then because it should be all or nothing; even several uFs then just a waiste of the cap ?

Thanks to Gus, he be the originator.