John Curl's Blowtorch preamplifier part II

[Steve Eddy]

Originally Posted by jam

Steve,
..............here is something more your speed.

Sorry, but that's waaaaaay over my head. Gimme a call tomorrow and 'splain it to me.

se

[Roxanne]

Originally Posted by scott wurcer

Download any recent issue of Elecktor and there are numerous listings for services at any level. I use ExpressPCB $51 for three 1/2 eurosize boards. Good for student projects.

Nice I like this site, im also interested in their software, i found this site which im referencing my friends at uni to Jackaltac - Home page , I dont know what their conditions are I think 5 pcbs per order but we usually to broke to buy more than like 3 ,but they the cheapest iv found so far

[jan.didden]

I get my boards from OLIMEX Ltd. - Electronic Design and PCB sub-contract assembly OEM/ODM service (see 'protoboards') charging euro 30 per eurocard, double sided incl plating, solder masks & top silk screen. These are professional boards.

jan didden

[Soundminded]

Originally Posted by john curl

Yes, I think so. Bogen, in Germany made the best contoured heads, and they were used on Studer machines. American heads had more ripples. Part of the problem is the WIDTH of the head. Skinny heads are awful!

Hyperbolic heads bad.

Parabolic heads good!

[gpapag]

Originally posted by Steve Eddy
I see you emphasized "Losses" in the title, but you overlooked "Windings."

Emphasis was on the "Losses" to make clear that the linked document deals with Eddy Current Losses only, with no hint of inference to Eddy Current Noise.

He says absolutely nothing about the core materials, which is what is being discussed here.

Correct, that’s why I didn’t include this link to my earlier post John Curl's Blowtorch preamplifier part II
But reading your:

Originally Posted by Steve Eddy
Which means that even a simple length of wire would also exhibit the same frequency dependent "eddy current noise," yes?

I was (and still I’m) under the impression that you were pulling a leg toward the skin effect and proximity effect (which are actually describing the action of eddy currents within the circuit’s current conductor own material).
If I failed to read correctly your message, my apologies, but please explain your message’s reasoning.

What we're talking about is audio transformers, which are using wires on the order of 42 gauge. With such small diameter wire, skin and proximity effect are effectively non existent at audio frequencies.

I agree that with such thin wires, they are not a realistic problem at audio frequencies. Fig. 15 of linked document verifies this. One more use for the link.

And again, it's not the windings that are at issue, but rather the alleged added noise due to eddy current losses in the core.

I am too after this assertion.

Regards
George

[Joachim Gerhard]

This is off topic but there was a terible earthquake and Tzunami in Japan. 8.8 on the Richter scale. I got in contact with Stig indirectly. His family is still in town but Tokio seems to be ok. As far as i know the atomic reactors have being swtiched of.

[gpapag]

8.9 on the Richter scale can not be OT. Thanks Joachim

As far as i know the atomic reactors have being switched off.

Japanese were already prepared
Nuclear Power Plants and Earthquakes

Regards
George

http://www-pub.iaea.org/MTCD/publica...ub1158_web.pdf

http://www-pub.iaea.org/mtcd/publica...e_1250_prn.pdf
http://www-pub.iaea.org/MTCD/publica...e_1347_web.pdf

[Joachim Gerhard]

Thats what my sources say. I was surprised too. Maybe it is a typo.
Anyway, it seems to be a desaster.

[DF96]

With regard to eddy current losses, one way to think of these is to add an extra winding to the transformer then put a resistor across the winding. This represents both a loss mechanism, and a source of thermal noise. The thermal noise is present whether there is a signal or not.

However, this might not be a perfect analogy as eddy current losses increase with frequency but a loaded secondary is flat. Perhaps a better analogy would be a loosely coupled secondary, so that the induced voltage rises with frequency but there is only a weak back reaction onto the primary.

[gpapag]

Thats what my sources say. I was surprised too. Maybe it is a typo.

It is not a typo (bottom of page)

Latest Earthquakes M5.0+ in the World - Past 7 days

Details:
http://earthquake.usgs.gov/earthquak...11/usc0001xgp/

Glossary of Terms:
http://earthquake.usgs.gov/earthquakes/glossary.php

Regards
George