John Curl's Blowtorch preamplifier part II

[PMA]

Tek scope has several immersed shielding cases - it IS very effective.

[bcarso]

Originally Posted by marce

Why do you assume that, I cant understand some replies, or the paranoia in the replies!
i am just giving some advice like many others do on this forum. PCB design just happens to be my area of expertease, and I am pretty much an expert in the design and assembly of PCB's and most aspects sourounding them.It does get my back up though when you get replies like yours Bcarso, I was not implying anything, so why reply in such a way, take a chill pill as my Kids would say

And you are saying I am touchy!

Look, you jump in here after Wayne asks about board material, and say that we shouldn't worry about that. And that we should worry about layout, as if Wayne and John and the rest do not. And each time you return and reiterate, you mention layout. It seems a not-unreasonable assumption to suppose you are suggesting we don't care about layout.

And where is this "paranoia"? This thread has been remarkably even-tempered of late, as things go.

Your insights into the evolution of PCB materials are welcome, and I'm confident that your own are of sufficient quality. I must however remind you that this is a global forum, and the opportunities for shoddy materials to slip into the manufacturing of equipment are abundant. I speak from bitter experience, in one case where a bad batch of ceramics used in 100nF capacitors practically killed someone, and cost the manufacturer about 1.5 million dollars in rework costs and momentarily shut down the shipping of computers by a major.

It is not unreasonable to suppose that, even in this day and age, circuit board materials could be of poor quality and still be shipped by a less-than-scrupulous vendor.

[wayne]

I would like to thank everybody for input on board materials. FR4 or 406 is my standard for usual work with 406 for power supplies. I have noticed that our production boards sound better than the prototypes do. Two different companies and slight physical differences in the boardslooks. Production boards are in Sunnyvale and they do good work and are offering me input on materials.
I haven't worked with Teflon in 25 years and there are so many choices today.
It may just be guilding the lily but I trust JC and his audio opinions. A bad layout as Marce pointed out can kill the whole thing I suppose that is why I like to do my own. Easier today with PCAD and Altium instead of mylar and tape. No wonder I have grey hair.

[john curl]

The TEK case would be OK. Want to design one for me?

[elektroj]

Here's the nice tutorial:
Tom Jerse and Mark Terrien, "A Designer's Guide To Shielding"
http://www.hparchive.com/seminar_notes/a-104.pdf
Apologies if it has been posted here before.

[john curl]

Thanks for the link: elecktroj

[marce]

Bsarso, ot touchy grumpy maybe, but it was not I who insinuated hat people dont care about layout, its you who jumped up and down.
As to jump in, its a public, Im allowed to jump in!
There are many here (many) who are new to electronics and PCB layout, what I was saying was that you dont have to worry about exotic PCB materials for audio and the best way of getting good results is learning layout properly, not concentrating on esoteric materials.
As to bad materials, yes you can get low grade FR4, but not if you go to a reptuble PCB manufacturer. There was a lot of 130 deg C TG stuff in the far east when lead free came in, which whilst not bad was realy unsuitable for lead free processing, a large amount of this got used up for consumer goods for a numbr of years ou could get silly prices on basic 2 and 4 layer boards from the far east.
I doo find your attack rather upsetting, and paranoid in nature. As to layouts on this site some are very good, the majority are god, and a few are mediocre. I was just airing a cooment and do not justify your attack, it was advice similar to the advice that others post, for the newer people to this sort of thing.
Its the same with EMC, good EMC design starts with the layout, get that right and your on to a winner.
Sorry to disapoint you but ood layout is the most critical aspect of PCB design,for EMC, thermal, signal integrity and a circuit that works. As to my designs, they have to be as near perfect as possible, as more often than not they are in life critical systems, something that is always is a the back of your mind, as failure could result in someones death. But I have also been lucky in a long and varied career to have worked with lots of interesting and clever people, from whom I have learned a lot, and as for myself have studied all aspecpts of PCB design, manufacture and assembly for over 25 years.
So I would ask you to desist with you silly allegations and real your neck in.
Again a bad layout with the best materials in the world is not gonna work is it!

[gpapag]

Originally Posted by elektroj

Here's the nice tutorial:
Tom Jerse and Mark Terrien, "A Designer's Guide To Shielding"
http://www.hparchive.com/seminar_notes/a-104.pdf
Apologies if it has been posted here before.

Thank you elektroj.
This is an excellent paper.

George

[jneutron]

Originally Posted by elektroj

Here's the nice tutorial:
Tom Jerse and Mark Terrien, "A Designer's Guide To Shielding"
http://www.hparchive.com/seminar_notes/a-104.pdf
Apologies if it has been posted here before.

I've never seen it before, thank you very much.

I note several important concepts for audio, all on page 6.
1. Near field, far field
2. 377 ohms
3. The E vs H impedance nearfield.

These concepts are significant when it comes to audio, low level, low impedance stuff. EMC theory expounds more along that line as well.

Kept my copy for reference...thanks again.

jn

[john curl]

I think that BOTH professional layout and superior board materials are necessary for 'WORLD CLASS' products. The CTC Blowtorch had both, as did the Vendetta Research phono stage.