So I recently received my Amp Camp Amp kit in the mail, and then promptly went on holidays for almost a month and hadn't had a chance to check out the parts that were included until now.
Turns out that the speaker terminals included are ferro-magnetic (i.e., some form of steel plated with gold or somesuch) rather than a non-magnetic alloy such as plated brass. Why does this matter? Well, after reading through Douglas Self's Audio Power Amplifier Design (6th ed., 2013), on pages 426-427 he talks about magnetic distortion introduced into a power amp's output by ferromagnetic speaker terminals. Turns out this is a thing, and introduces detectable third-order harmonic distortion. Does anyone know where I can obtain speaker terminals that are guaranteed NOT to be ferro-magnetic? The usual sources have all managed to fail me so far, which is annoying. I've probably ordered close to 100 dollars' worth of terminals from various sources (eBay, various Canadian electronics distributors, Parts Express) and all of them have been attracted to the magnets I've waved over 'em, even though they've all claimed to be plated brass.
Turns out that the speaker terminals included are ferro-magnetic (i.e., some form of steel plated with gold or somesuch) rather than a non-magnetic alloy such as plated brass. Why does this matter? Well, after reading through Douglas Self's Audio Power Amplifier Design (6th ed., 2013), on pages 426-427 he talks about magnetic distortion introduced into a power amp's output by ferromagnetic speaker terminals. Turns out this is a thing, and introduces detectable third-order harmonic distortion. Does anyone know where I can obtain speaker terminals that are guaranteed NOT to be ferro-magnetic? The usual sources have all managed to fail me so far, which is annoying. I've probably ordered close to 100 dollars' worth of terminals from various sources (eBay, various Canadian electronics distributors, Parts Express) and all of them have been attracted to the magnets I've waved over 'em, even though they've all claimed to be plated brass.
Vampire wire BP3 or the hex are non magnetic and what we use on first Watt.
The nuts are magnetic though but I wouldn't worry about that.
The nuts are magnetic though but I wouldn't worry about that.
The Pomonas are quite nice for the cost. Remember the input sockets, too.
Superior Electric (with no N suffix) https://www.newark.com/superior-electric/bp30r/binding-post-30a-8-32-stud-red/dp/35F3006
Pomona tellurium copper Binding Post, Low Thermal Emf. Tellurium-Copper, Gold-Plated | Pomona Electronics
Vampire Vampire Wire BPHEX/CB Binding Post (Set of 2)
Last edited:
Gold plating - Wikipedia
"Gold plating is often used in electronics, to provide a corrosion-resistant electrically conductive layer on copper, typically in electrical connectors and printed circuit boards.
With direct gold-on-copper plating, the copper atoms tend to diffuse through the gold layer, causing tarnishing of its surface and formation of an oxide and/or sulphide layer.
A layer of a suitable barrier metal, usually nickel, is often deposited on the copper substrate before the gold plating. The layer of nickel provides mechanical backing for the gold layer, improving its wear resistance. It also reduces the impact of pores present in the gold layer."
Nickel is of course magnetic.
Cheers,
Patrick
"Gold plating is often used in electronics, to provide a corrosion-resistant electrically conductive layer on copper, typically in electrical connectors and printed circuit boards.
With direct gold-on-copper plating, the copper atoms tend to diffuse through the gold layer, causing tarnishing of its surface and formation of an oxide and/or sulphide layer.
A layer of a suitable barrier metal, usually nickel, is often deposited on the copper substrate before the gold plating. The layer of nickel provides mechanical backing for the gold layer, improving its wear resistance. It also reduces the impact of pores present in the gold layer."
Nickel is of course magnetic.
Cheers,
Patrick
plated brass is not magnetic, however screw nuts and solder lugs used on speaker terminals could be - I just tried it on a visaton speaker terminal...
You could most possibly replace nuts and lugs with brass ones.
You could most possibly replace nuts and lugs with brass ones.
Last edited:
Thanks, Juergen (and everyone else). Yeah, some of the terminals I've got only display magnetism on the nuts and lugs, which is odd. And yes, I'm already sourcing components to replace those items with ones that are either brass (gold-plated or not) or with some other metal/alloy that doesn't display ferromagnetic properties. Should be interesting. I'll report back on my findings in a while.
Use stainless steel ones, SS304 or 306
Easy to get, won't rust, or break up.
Don't trust Chinese stuff.
Get wing nuts if you want, or knurled ones, for ease of use.
And don't pay too much attention to third order harmonics, they are 30 dB or so down, more marketing than anything else.
“3% distortion,” instead of the correct reference to “3% third-harmonic distortion” – quite different things.
OP last activity 13 June 2021....
Easy to get, won't rust, or break up.
Don't trust Chinese stuff.
Get wing nuts if you want, or knurled ones, for ease of use.
And don't pay too much attention to third order harmonics, they are 30 dB or so down, more marketing than anything else.
“3% distortion,” instead of the correct reference to “3% third-harmonic distortion” – quite different things.
OP last activity 13 June 2021....
Last edited:
I'm not sure what the base metal is on these but mine are not at all magnetic.
Dayton Audio BPP-NI Premium Binding Post Banana Jack Pair Nickel
Dayton Audio BPP-NI Premium Binding Post Banana Jack Pair Nickel
I have been here, just not on this thread.
Garth Wood was last seen on this forum in June 2021, and he was the thread starter.
As an aside, we have a city called Jamnagar, famous for brass parts, and there also the quality has suffered as they used cast rods made from scrap, instead of extruded rods.
They have automatic lathes, and the process generates a lot of scrap...some was melted into thin rods.
Porosity, burnt cutting oil, tool steel residues were among the problems.
Terrible.
Garth Wood was last seen on this forum in June 2021, and he was the thread starter.
As an aside, we have a city called Jamnagar, famous for brass parts, and there also the quality has suffered as they used cast rods made from scrap, instead of extruded rods.
They have automatic lathes, and the process generates a lot of scrap...some was melted into thin rods.
Porosity, burnt cutting oil, tool steel residues were among the problems.
Terrible.
Brass is about 60% Copper and the rest Zinc.
I prefer solid Copper screws, Cu terminals, Cu lugs setups, than Gold plated. I can measure Microvolts/millivolts across connectors of any different metals. Think along the lines of thermocouples generating thermal generated voltages made by speaker current flowing through.
I prefer solid Copper screws, Cu terminals, Cu lugs setups, than Gold plated. I can measure Microvolts/millivolts across connectors of any different metals. Think along the lines of thermocouples generating thermal generated voltages made by speaker current flowing through.