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Old 22nd February 2013, 12:59 AM   #35691
qusp is offline qusp  Australia
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if for high frequency like RF or higher, i'll maybe be a little lonely here, but use the absolute smallest ceramic SMD you can see/solder in the correct value and as close to the pin as you can, preferably via in pad, or off to the side of the pad for lowest inductance
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Old 22nd February 2013, 01:20 AM   #35692
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And remember that capacitance in and of itself does not damp, but lowers the resonant frequency. Lossy caps will do some of both.

One sees caps across power diodes to reduce the effect of reverse recovery spikes. But these help by reducing the resonant frequency due to the external circuit inductances etc., which then reduces the ability of the ringing to propagate into other parts of the circuit.
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Old 22nd February 2013, 01:41 AM   #35693
qusp is offline qusp  Australia
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yes I was going to suggest tants or X7r not c0g for that reason, but didnt want to overwhelm off the bat. depending on the circuit, some small resistance or resistance built into the PCB trace can be placed in series to help damp. also remember that once things get up to really high frequency, no cap will help you that much, planar cap in the PCB planes is about as close as you'll get at that stage.

and ferrites of course

Last edited by qusp; 22nd February 2013 at 01:49 AM.
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Old 22nd February 2013, 02:48 AM   #35694
bcarso is offline bcarso  United States
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Originally Posted by qusp View Post
yes I was going to suggest tants or X7r not c0g for that reason, but didnt want to overwhelm off the bat. depending on the circuit, some small resistance or resistance built into the PCB trace can be placed in series to help damp. also remember that once things get up to really high frequency, no cap will help you that much, planar cap in the PCB planes is about as close as you'll get at that stage.

and ferrites of course
My preference for top drawer work would be to have low loss C and adjust external lumped R to optimize. And ferrites are fine for the really HF stuff.

Also the soft recovery diodes to begin with, but that would lead me into another story, and I still owe the one about the late Jack Ryan. The Story Deficit is burgeoning. Better a virgin or a sturgeon than a burgeon.

Mas de Libyan "Khayyam" 2009 Cotes du Rhone, since someone asked. Outstanding, one of WineAccess hits out-of-the-park. Significantly nicer now than a year ago. Four bottles left.
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Old 22nd February 2013, 02:48 AM   #35695
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Thank you for the answers. I better keep reading my books by Self and Cordell. Someday I may understand half of what the rest of you all know.
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Old 22nd February 2013, 02:51 AM   #35696
bcarso is offline bcarso  United States
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Thank you for the answers. I better keep reading my books by Self and Cordell. Someday I may understand half of what the rest of you all know.
Reading books is almost always good. For a while I tended to be much better at acquiring them than reading them, but the tide is turning.
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Old 22nd February 2013, 04:18 AM   #35697
qusp is offline qusp  Australia
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My preference for top drawer work would be to have low loss C and adjust external lumped R to optimize. And ferrites are fine for the really HF stuff.
I know, ferrites are fine, the evil smile was just that I feel sure there are some members in this thread that are already sneering at my pro SMD stance, but an SMD ferrite in a low noise design? the shame!

re your fave technique with lumped R, I just bought some of the new AVX GX thin film for playing with exactly that on a clock reg i'm toying with, to use as part of a compound filter. impedance controlled PCBs are too expensive and I dont have the modelling warez/chops to pull it off as yet.

its not something you can do blind though, as Marce reinforced to me today, the lower loss the cap, the stronger the resonant peak, narrower, but higher; its all gotta come out somewhere. the 'look mom no hands' approach would be the lossy cap I reckon, again depends on the job.

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Also the soft recovery diodes to begin with, but that would lead me into another story, and I still owe the one about the late Jack Ryan. The Story Deficit is burgeoning. Better a virgin or a sturgeon than a burgeon.
yes lets not go there, we dont even know what specifically Steven has in mind.

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Mas de Libyan "Khayyam" 2009 Cotes du Rhone, since someone asked. Outstanding, one of WineAccess hits out-of-the-park. Significantly nicer now than a year ago. Four bottles left.


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Thank you for the answers. I better keep reading my books by Self and Cordell. Someday I may understand half of what the rest of you all know.
no problem Steven, on this subject (EMC and Signal integrity), I dont think you can go past Henry Ott (hottconsultants.com) his book Electromagnetic Compatibility Engineering is superb. hes not specifically an audio designer, but for PCB design of all types I believe hes da man.

if you can make an RF instrumentation amplifier quiet in todays higher and higher frequency poluted mixed signal world, youve got a good start on Audio frequencies... they really are not special frequencies, they are just frequencies that happen to fall in and near the audible range...

his digital and mixed signal design tips, even what he gives away for free on his website tackle many of the problems people argue endlessly about here, in an easy to understand and matter of fact way.

Highly recommended! I gather hes something of an expert's expert. you can maybe find this whopper (892 pages) used if you are lucky, but just start with the free stuff.

starting here Decoupling it covers basic technique for low frequencies, right up to 5GHz and tackles exactly what we are saying here, that throwing a couple different arbitrary size caps at a design has been the default for 40years, parts have changed somewhat.... so a more varied approach is needed

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Decoupling is not the process of placing a capacitor adjacent to the IC to supply the transient switching current, rather it is the process of placing an L-C network adjacent to the IC to supply the transient switching current. The inductance comes from the capacitor itself (typically 1-2 nH for a SMT capacitor), the interconnecting traces (typically 5 to 20 nH according to the layout), and the lead frame of the IC (typically 4 to 15 nH according to the type of IC package). From the above we see that the inductance can vary from a low of 10 nH to a high of 37 nH, all assuming a reasonably good layout. It is this inductance that limits the effectiveness of the decoupling network. It is very important to remember this fact -- we are placing an L-C network between the power and ground, not a capacitor!

Henry Ott
he also goes into great detail about via placement arrangements and the specific inductance of each type. Stuff thats often not covered in Audio amplifier books, you dont have to be wanting to design PCBs to get a lot out of it.

also Distinguishing Between C-M and D-M Conducted Emission

hes a big believer in ground planes and multilayer design, as am I, but be warned those who think them evil.

I'm indebted to Marc for recommending him to me, it covers so much that i've been running the wagons around and as in depth as you like.

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Reading books is almost always good. For a while I tended to be much better at acquiring them than reading them, but the tide is turning.
I think you would love it too!

no affiliation, I just think we should all own it, group buy?

Last edited by qusp; 22nd February 2013 at 04:24 AM.
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Old 22nd February 2013, 05:41 AM   #35698
RNMarsh is offline RNMarsh  United States
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Cookies must be enabled. | The Australian

Tjapaltjarri, Clifford Possum - Artists - Australian Art Auction Records

Average price $20,107....no idea if yours is above average price, or below average price....either way it looks like you can't lose.

I have a mate who has a large Albert Namatjira painting....no idea of the 'value', but I do believe it is sizeable.

Dan.
Thanks for the source info ... I paid $1K for his work... more than I paid for the other aboriginal artists. Clifford Possum fetched 1.2 and then 2.4 million usd at sothebys in Australia a couple years ago, I have video of him signing my piece. One of the few ways one knows it isnt a painting someone else did and put his name on it to fetch a better price -- which as been going on. Now I can look it up -- Excuse me Scott !

I knew this was the right place as so many are interested in art of all forms besides music. The artist died (2001) and that always raises the ante. maybe I can trade it for a Blowtorch?

Thx-RNMarsh

Last edited by RNMarsh; 22nd February 2013 at 06:00 AM.
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Old 22nd February 2013, 06:50 AM   #35699
1audio is offline 1audio  United States
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Using careful design and good RF practice seemed to work well for me along with a rational approach to component selection, all consistent with Morrison and Ott.

But Ott doesn't talk about the mechanical resonances of capacitors and how important that is. Here is a "paper" that refers to a BLIND test of 30 observers that supposedly validates the nonresonant construction of caps with stuff like paper and beeswax. It gets really interesting when the author discusses intermodulation distortion at double the audio frequency.

I really need to learn to leave rational science behind, I have missed a gold mine in selling fuses for $70+ Synergistic Research Quantum Fuse Large FB

I would really like to see the UL test report for the fuses.
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Old 22nd February 2013, 07:01 AM   #35700
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I really need to learn to leave rational science behind, I have missed a gold mine in selling fuses for $70+ Synergistic Research Quantum Fuse Large FB
Looks like they're taking a cue from Bybee.

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