[Roger A. Modjeski]

Thanks for PF for the link to the Bell Labs article on Silver Migration. http://alcatel-lucent.com/bstj/vol34-1955/articles/bstj34-6-1115.pdf

This perhaps explains why I have seen shorted silver capacitors in amplifiers I have repaired. The Bell article is technical, as one would expect but here is the crux of it and what I learned.

Silver is routinely used to make good switch contacts because even when oxidized (the tarnish you see on your silverware) it is still very conductive. The telephone system at the time of this paper (1955) was evidently having leakage problems with the rotary switches in the dialing system. The problem is that silver was migrating from the contacts onto the insulators between the contacts and degrading the insulation over time. The numbers are astounding. In a complete path the resistance had degraded from 1000 meghoms to 0.03 megohms which is almost a short in telephone circuits.

The further found that the type of insulation mattered. Paper of any kind was the worst and plastics of any kind was the best insulator. What happens over time is that the silver forms dendrites (little needle paths) on the surface of the insulator causing the leakage.  This article perhaps explains the problems I have seen with silver capacitors.

Silver capacitors are though to be the finest. Once again part of this thinking is that since silver is the best conductor we should use that in capacitors. I wonder how many makers of silver capacitors are aware of migration? Don't make the assumption many have made about the fuse makers having done their homework, because we know they have not.

Many silver capacitors are made with paper insulators as described in the PF article on the Tannoy Westminster Crossover Project.  In a coupling capacitor the insulation must be very good. It is good to hear that Duelund is aware of the problem. The question is how well have they solved it if it can be solved at all. I have heard from audiophile acquaintance that although he likes the sound of Duelund capacitors in his amplifier they tend to fail after about a year. In a power amp that could also cost the loss of an expensive 300B.

Thank you to PF and Bell for enlightening me on one of the problems of silver. Bell also tested aluminum and found it to have the lowest migration of all the metals. In a capacitor the resistance of the metal is so small that it will not enter into the equation of a well made capacitor where all the foil is in parallel thus forming a very low resistance (low ESR) part.

I prefer polypropylene or Mylar capacitors which just happen to use aluminum as the electrode and tend to last forever. They have a long history dating back to the 1960s when Mylar became the preferred insulating material for capacitors.

[bdp24]

Does this call into question the use of high purity silver wire in interconnects and speaker cables? There are some made using solid core silver wire, others with stranded. Then there are silver coated copper wire cables. My head hurts .

[Roger A. Modjeski]

Does this call into question the use of high purity silver wire in interconnects and speaker cables? There are some made using solid core silver wire, others with stranded. Then there are silver coated copper wire cables. My head hurts .

I think it does not cause a problem in low impedance speaker cables. It might cause a problem at the connection points of an interconnect where the silver can migrate over the insulator which is exposed to the atmosphere. For those who read the article it was found that moisture or silver dust is required for migration. Keep your powder (interconnects) dry boys.

I might note here that all Teflon hook-up wire comes silver coated. It is part of the process of making standard Teflon wire so don't get too impressed by that. Teflon wire from Radio Shack is silver coated. This does not necessarily apply to speaker cable where the a large Teflon sleeve is placed over a group of conductors.

The migration of silver concerns me most in capacitors as over time it can cause them to become electrically leaky or short out. Unless a cap is hermetically sealed, moisture will get in over time. Paper is the worst insulator in that instance as shown by the Bell paper. I would like to hear if any of you has had problems with silver caps.

I recently worked on some older Japanese amps that had high quality oil and paper caps. I had to replace all of them (20 pcs). I tested each one both in circuit and out. They all had enough leakage to move several operating points by 10-20 volts (15-30%) and cause the amplifier to have reduced power and distortion.  Often a tech will replace all caps when he finds a few bad ones. This was not the case, they were all bad.

While some think caps of exotic materials may sound better, in my experience they are an invitation to problems.

[BobRex]

I might note here that all Teflon wire comes silver coated. It is part of the process of making standard Teflon wire so don't get too impressed by that. Teflon wire from Radio Shack is silver coated. We use a lot of Teflon wire in our products.

Are you sure about that?  Kimber 8TC is Teflon and is pure copper, there is no silver coating.

[Roger A. Modjeski]

Are you sure about that?  Kimber 8TC is Teflon and is pure copper, there is no silver coating.

I was speaking of Teflon hook up wire where I was told that the silver was needed for the extrusion process. My point was to inform the public that silver coated Teflon wire is not special. I will modify my post to clarify that. Thanks

I see it can be made without. Is the insulation tight on the Kimber? Are the individual conductors separately insulated or is there one Teflon sleeve over plus and one over the minus as it appears in the photo?

[BobRex]

Yes, the insulation is tight.  The cable is a braided cable where each Teflon lead houses multiple strands of bare copper.

[Roger A. Modjeski]

Yes, the insulation is tight.  The cable is a braided cable where each Teflon lead houses multiple strands of bare copper.

If I understand correctly the Teflon is likely put over the wire as a sleeve rather than being extruded over the wire. Perhaps that is what "cold extruded" means in their specs. They do have pretty impressively low inductance.

[corndog71]

I was speaking of Teflon hook up wire where I was told that the silver was needed for the extrusion process. My point was to inform the public that silver coated Teflon wire is not special. I will modify my post to clarify that. Thanks

I see it can be made without. Is the insulation tight on the Kimber? Are the individual conductors separately insulated or is there one Teflon sleeve over plus and one over the minus as it appears in the photo?

Each wire is individually insulated.  "The insulating dielectric is high pressure, low temperature extruded fluorocarbon."

[Roger A. Modjeski]

Each wire is individually insulated.  "The insulating dielectric is high pressure, low temperature extruded fluorocarbon."

nice picture, thanks. Do you have a link to that on more?

[corndog71]

http://www.kimber.com/about/

Also, if you give them a call, I'm sure they can tell you more.  They're pretty friendly.

[Roger A. Modjeski]

http://www.kimber.com/about/

Also, if you give them a call, I'm sure they can tell you more.  They're pretty friendly.

Thanks, I have met Ray, he is a good guy, happy to have him in the industry.

[kenkirk]

I was speaking of Teflon hook up wire where I was told that the silver was needed for the extrusion process. My point was to inform the public that silver coated Teflon wire is not special. I will modify my post to clarify that. Thanks

I love to use Teflon hook up wire in my tube amp restorations because I can put the heat to it and the insulation won't discolor or melt. Within reason.  Also I am guessing that the Teflon insulation will still be flexable and doing its job for 30 years or more.  I make no claims that it sounds Superior to plain copper hook up wire.

Ken

[BobRex]

This is probably a good place to ask this - wire quality.  There are a plethora of wire vendors that use POCC or other low crystal count copper and silver.  Given the yards / miles of copper in an output transformer,  (as well as component leads and other connections) does that 3 feet of super wire really make a difference?

[corndog71]

I've read about dendrites before.  I think this was it.  Not exactly the same but similar phenomenon.

http://www.empf.org/empfasis/2009/may09/tin.html

[Roger A. Modjeski]

This is probably a good place to ask this - wire quality.  There are a plethora of wire vendors that use POCC or other low crystal count copper and silver.  Given the yards / miles of copper in an output transformer,  (as well as component leads and other connections) does that 3 feet of super wire really make a difference?

I think 3 feet of wire makes no difference at all. What really amuses me is when I get a head amp or preamp and see a 1 inch piece of exotic,  heavy, hard to work with wire from the input jack the PC board. Like this inch of wire is going to make a difference. 

We use good wire in our transformers but I don't know if anyone is making exotic magnet wire. I sincerely hope I never have to deal with that issue.

[llwhtt]

That's my take on "magic power cords", you have miles and miles of "normal wire" from Hoover Damn to your house and then the last magical six feet is going make a difference?

Craig

[/mp]

or even a hundred feet from circuit breaker to outlet. Still waiting for a valid explanation of this one. But not holding breath.

[/mp]

How does magnet wire differ from other wires?

[Roger A. Modjeski]

That's my take on "magic power cords", you have miles and miles of "normal wire" from Hoover Damn to your house and then the last magical six feet is going make a difference?

Craig

or even a hundred feet from circuit breaker to outlet. Still waiting for a valid explanation of this one. But not holding breath.

It amazes me the claims made for power cords and the magic people think they do. The most amusing to me is when they replace a polarizing cord on a QUAD ESL and report an improvement. The polarizing supply draws less than an electric clock. You can play the speaker for some time after charging it up. I wonder what no power cord sounds like.

[Roger A. Modjeski]

How does magnet wire differ from other wires?

The wire we wind coils and transformers with has traditionally been called Magnet Wire as it was first used to make electromagnets.  It is a single conductor of drawn copper coated with a thin lacquer so as not to add much to its diameter. I buy good American made magnet wire . Paul Speltz and I sell it for speaker wire for those so inclined. We think it sounds good.