Binding posts and metal conductivity?

F1nut

So, I'm looking at binding posts for a project and like the look of some from Furutech, but notice they are using plated phosphorus bronze. Looking up the conductivity of different metals shows its fairly low on the list, which has me wondering why a company known for making high quality connectors would use a seemly inferior metal or does it not matter that much as long as it's plated?

txcoastal1

Cardas

txcoastal1

txcoastal1 wrote: »

Cardas

If that doesn't work PM @helipilotdoug
I know he jacks with the distributors more than others

F1nut

I've been using Cardas for years, but was looking for something different on this project.

txcoastal1

Copper with silver plating IMHO best
Sure silver tarnishes but slowly, and easy cleanup and the combo has least impedance

I know you know this but.....just saying

F1nut

Agreed and that's why I'm perplexed at Furutech using phosphorus bronze.

If anyone has some insight on that matter, please speak up.

In the meantime, I found some from WBT that look very promising, pure copper conductor plated with silver or gold and not too obscene.

F1nut

I think these will do nicely. I wanted something other than shiny gold or silver, but the main focus is the sound quality. This is the gold plated version.

Joey_V

Is there a noticeable difference in sound between bindings posts?

Just curious.

motorhead43026

I would think what it is plated with matters more to its conductivity.

BlueFox

From Shunyata.

"Outside of top quality commercial outlets such as Spec grade Leviton and Hubbell, there are now many brands of specialty "Audio-Grade" outlets on the market, some costing hundreds of dollars or more. These outlets often have special contact plating, polished surfaces, unique material and metal treatments. What's notable about all of them is that they will invariably sound different from one another and subjective preferences will often play a role in choosing one over another. Just as with after-market power cords, more expensive does not necessarily mean better no matter how precious the metals are.

The critical elements in selecting an outlet for applications related to sound and recording are covering the basics of conductivity and a secure connection. This means that there should be high quality conductive base metals used for the contact points and that there are broad heavy gauge contact surface areas internally. Contact points for wire should also have generous space for 10 gauge wire termination and broad brass or copper base metal surface areas. Outlets with wide internal chassis are preferable for their better air cooling properties and reduced heat at contact points.

Silver, gold and nickel plating may seem like a plus but "premium metal plates" often have obvious or overt sound characteristics -- one warm and rich while others are sharp, cool and lean. Contact platings do not enhance DTCD™ nor do they provide measurable noise reduction. Most often these simply act as tone-shifting elements rather than an enhancement to connectivity. As is often true in high-performance markets where price extremes exist -- more often the best value and performance solutions lie in the more reasonable price ranges and with the more explainable science."

http://www.shunyata.com/index.php/support/faqs

motorhead43026

AC travels on the surface of the conductor. So the plating would come in play more than the underlying material.

[Deleted User]

One consideration is the diode effect of plating two dissimilar metals, such as a thin gold plating over solid copper. Mitchell Cotter always advocated a fairly thick silver plating for all of his connectors, believing that even when there's a slight oxidation of the silver the result is still a great conductor and the diode effect seems very small. In my semi-humble opinion it is better to have a solid core material with no coating especially if a thin one.

gp4jesus

Jesse, trust YOUR gut on material.

In this case Gold plating is a well painted car hiding buckets of putty - that will reveal itself sooner or later. Further, copper cladded 8 gauge aluminum has the same conductivity as 10 gauge copper but likely different SQ.

Tony

gp4jesus

motorhead43026 wrote: »

I would think what it is plated* with matters more to its conductivity.

Only if you're relying upon same* to carry ALL the signal. Gold doesn't corrode minimizing that issue. it's the BPs "foundation," kinda like a sub doing a HT's heavy lifting, that provides 98%+ of signal transfer.

mhardy6647

motorhead43026 wrote: »

AC travels on the surface of the conductor. So the plating would come in play more than the underlying material.

The skin effect depends on frequency -- more of a factor at MHz than sub kHz -- at least acccoring to engineers.

(and I am, as you know, not an engineer)

PS What kind of ears do engines have?

Engineers.



Ken's point about dissimilar metals (junctions) is a good one -- I have no idea what audible effect it might have... but it may impact the physical longevity of certain really poorly chosen pairs of metals (one has made a Galvanic cell -- whether intentionally or not).

How the above play into the always somewhat murky world of audiophilia are impossible for me upon which to speculate, though.

kharp1

How expensive are the Furutechs? Reasonable enough to give them a try? Realize it could be pita to switch them out, but, it's one way of finding out.

F1nut

Thanks everyone for your insights. I ordered the WBT posts pictured above from Hifi Collective in the UK because they were significantly cheaper even with shipping. I went with the gold plated version because every other connection in the chain will be gold plated.

I might give Furutech a call anyway to ask what their reason is for using phosphorus bronze.

rpf65

The phosphorus will allow the bronze to flow more evenly and cause it to better adhere to the copper. Believe that bronze won't oxidize as quickly as copper, but could be mistaking.

Don't know what colorization, if any, it would change from pure copper.

mhardy6647

"Phosphor bronze" was a traditional, widely used material for connectors for decades in electronics. I had assumed that the flexibility (vs. brittleness) of the material for 'spring-loaded' quick connect/disconnect applications (e.g., banana plugs or Fahnestock clips) was better for phosphor bronze -- I didn't know about solder-friendliness. I thought improved flow was largely in the bailiwick of flux.

Heh, maybe some of what I believed is true, but maybe not all - imagine that?
https://en.wikipedia.org/wiki/Phosphor_bronze

rpf65

Use sil-phos to weld A/C line sets. Was told numerous times that the phosphorus was used for flux as well as a more consistently even flow.

pitdogg2

I remember a very well known audio company speaking of their binding post and bananas saying they used "inferior" base metals with top quality plating metals because they wanted the signal to stay on the better plating metals instead of getting down into the base metal.

My ears must be trashed because I have never heard any difference in your better binding posts or bananas and I have tried a few.

mhardy6647

rpf65 wrote: »

Use sil-phos to weld A/C line sets. Was told numerous times that the phosphorus was used for flux as well as a more consistently even flow.

Could well be!

MrBuhl

Interesting thread here. Enjoying the knowledge share.

DarqueKnight

mhardy6647 wrote: »

motorhead43026 wrote: »

AC travels on the surface of the conductor. So the plating would come in play more than the underlying material.

The skin effect depends on frequency -- more of a factor at MHz than sub kHz -- at least acccoring to engineers.

Motorhead is correct. Skin effect applies to a solid conductor of the same material. Since electricity takes the path of least resistance, when a lower conductivity metal is plated with a metal of significantly higher conductivity, most of the current will flow in the higher conductivity plating.

F1nut wrote: »

So, I'm looking at binding posts for a project and like the look of some from Furutech, but notice they are using plated phosphorus bronze. Looking up the conductivity of different metals shows its fairly low on the list, which has me wondering why a company known for making high quality connectors would use a seemly inferior metal or does it not matter that much as long as it's plated?

In the case of the Furutech posts, the conductivity would depend largely on the plating.

Phosphorous bronze is easier to cast and machine and has high strength, but lower electrical conductivity compared to copper and brass. Phosphor bronze also has much lower thermal conductivity than copper and results in less heat load in high current electrical applications.

DarqueKnight

xcapri79 wrote: »

DarqueKnight wrote: »

Since electricity takes the path of least resistance...

Correction, electricity takes all available paths in inverse proportion to the impedance of the paths. This is a key to understanding basic current flow in circuits and most importantly electrical safety.

Apparently, you were in such a hurry to correct me that you failed to read the rest of my statement. Please note the part highlighted in red:

DarqueKnight wrote: »

Skin effect applies to a solid conductor of the same material. Since electricity takes the path of least resistance, when a lower conductivity metal is plated with a metal of significantly higher conductivity, most of the current will flow in the higher conductivity plating.

Please explain how my saying "most of the current will flow in the higher conductivity plating" is in conflict with you saying "electricity takes all available paths in inverse proportion to the impedance of the paths".

Why did you remove this nice picture you posted with your "correction"?:



Below is a chart showing the conductivities of various metals compared to copper. We see that phosphor bronze has 4.67 times the resistivity of gold. The Furutech binding posts in question have a phosphor bronze base with a heavy plating of 24K gold. If we roughly model the two metals by letting the phosphor bronze be represented by a resistor of 10 ohms and the gold be represented by a parallel resistor of 46.7 ohms, and send a 5 amp current, 4.12 amps will pass through the gold and 0.88 amp through the phosphor bronze.

R(total) = (10)(46.7)/(10+46.7) = 8.23 ohms

I(10 ohm resistor) = [R(total)/10 ohms] x 5 amps = 4.12 amps (gold)

I(46.7 ohm resistor) = [R(total)/46.7 ohms] x 5 amps = 0.88 amp (phosphor bronze)

Another point that is often overlooked is that lower conductivity can be addressed with making the conductor bigger. For example, copper is 5% less conductive than silver. However, making a copper conductor 5% bigger will provide equal conductivity to silver in a given application.


Source: https://www.bluesea.com/resources/108

DarqueKnight

Joey_V wrote: »

Is there a noticeable difference in sound between bindings posts?

Just curious.

For some people yes...depending on their ears, system, room, and the type of music they listen too. Some of the members of this forum, myself included, easily hear differences between stock binding post jumpers and those of higher quality. I have not (yet) heard a difference between the stock binding posts on my SDAs and higher quality posts from Vampire and Cardas. However, I have not done a critical evaluation of binding posts and do not intend to due to the significant amount of assembly and disassembly work involved.

Nightfall

...or for our resident "geniuses"

nooshinjohn

X trying to school a published and distinguished electrical genius like D.K... just can't stop laughing out loud at that one. Kind of like an infant trying to teach their parents how to ride a bicycle.

F1nut

Well, this got lively.

DarqueKnight

xcapri79 wrote: »

Oh where do I start....

A good place to start is by understanding that the heavy 24K gold plating of a premium binding post will have different conductivity characteristics than the thin gold plating used on common commercial grade electronic parts.

The paper you cited (http://www.te.com/documentation/whitepapers/pdf/aurulrep.pdf) is focused on gold plating of contacts in industrial applications, (where durability of the contact surface is of paramount importance), rather than high performance audio applications where signal integrity is of paramount importance.

But lets assume that you are correct and that Furutech designed their gold plated phosphor bronze binding posts so that the mass of the bronze overcame its lower conductivity. Now there is a big electrical noise issue to deal with because the bulk of the current would travel through the electrically noisier bronze part. In that case, F1nut's initial reservation is reasonable and the technical advantage of their design is questionable since it purports to be "high performance".

xcapri79 wrote: »

There are so many errors in your explanation.

My explanation was sound and makes sense within the context of high performance stereophonic audio. The "one size fits all" mentality often induces one to error because the requirements of signal integrity are not properly considered.

xcapri79 wrote: »

I said, "Hence the plating has a relatively insignificant role in the total current flow, since most of the current flow will still be in the body of the terminal." This is because the plating is extremely thin, in the order of 0.03 microns (1 microinch) and 2.5 microns (100 microinches). It provides for low contact resistance but doesn't conduct the bulk of the current, even though all of the current passes through it since the plating completely surrounds the terminal.

So your analogy is inaccurate in terms of the proportion of current that flows in the gold plating vs the current that flows in the phosphor bronze terminal.

Again, the paper you cited primarily concerns electrical contacts in industrial applications where preventing corrosion and contact resistance are the goal, rather than preserving the integrity of a AC signal carrying stereophonic information.

xcapri79 wrote: »

Your metal conductivity table helps to bear this out. (I've pointed this out before when I corrected other members here on the conducting value of silver vs copper conductor.) The significant bulk of the terminal, by orders of magnitude, is phosphor bronze and its total resistance will be significantly smaller allowing the significant majority of the current to flow through it.

But you don't know the thickness of plating on the Furutech posts, nor do you know the exact chemical composition of their phosphor bronze composition and its resultant conductivity, nor do you know the relative mass proportions of the plating and base metal, nor do you know the noise characteristics of the base metal compared to the plating. I don't either. I'm giving Furutech the benefit of the doubt that they wouldn't design a noisy binding post. F1 said he was going to contact Furutech about it...perhaps then the mystery will be solved.

xcapri79 wrote: »

I removed the nice picture concerning electrical safety since the detail was a little off topic and may be confusing to some of the readership.

Oh, OK. That was very thoughtful of you.

gp4jesus

Since this thread I s about binding post construction, Polk on the left, Dayton on the right.




I'm confident I'll have LESS loss w/the Dayton regardless of base material - brass I think but I'll get back to y'all.

Tony