Hi !
Some Builder claim that copper chassis are more noiseless than aluminium..
I think that is more a question of grounding schem.. ?
Whant do you think ?
Copper chassis ?
Moderators: pompeiisneaks, Colossal
Copper chassis ?
Last edited by DaveWell on Tue May 23, 2017 1:09 am, edited 1 time in total.
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pompeiisneaks
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Re: Copper chassis ?
I don't know what data they have for that, but a copper chassis would be ridiculously expensive, The base metal prices for aluminum per lb is .87c vs 2.53 for a lb of copper. so that's 3x more expensive... Sounds like a nice 'con' 
I remember reading that Ken Fisher said that aluminum wasn't magnetic so it reduced the magnetic coupling that could happen in an amp, and copper is definitely magnetic, but I'm not sure there's tons of proof that aluminum is significantly better at hum rejection, all the old amps used steel and seem fine ;D
~Phil
I remember reading that Ken Fisher said that aluminum wasn't magnetic so it reduced the magnetic coupling that could happen in an amp, and copper is definitely magnetic, but I'm not sure there's tons of proof that aluminum is significantly better at hum rejection, all the old amps used steel and seem fine ;D~Phil
tUber Nerd!
Re: Copper chassis ?
My understanding is that steel is better than aluminum for hum rejection. Aluminum has virtually no magnetic properties which means it can't shield against electromagnetic interference, or in other words it doesn't shield against inductive coupling. It will shield against electrostatic (capacitively coupled) interference. Steel will shield against both. I've built amps using both materials and it really doesn't seem to matter as far as a guitar amp is concerned. Though I can't really address Ken's claim directly. I've seen that one as well. In theory though a solid steel chassis should be better at reducing induced hum from say a large nearby mains transformer or what not but eh. I prefer aluminum, its lighter and easier to work with.
I work in the audiophile industry so I will say this. There are a lot of companies out there that make a lot of really fantastic sounding products. There are also a lot of people out there that have great ears and can appreciate the sound of these products. There also a lot of people who have lots of money and are looking for something fancy to spend it on. So you'll see a lot of products with flimsy justifications for added fancy-ness, and you can hardly blame them for it too. If you have two products all else being equal and someone wants to drop 100k on a stereo system, then the one with all the outlandish claims and fancy metalwork will probably win out. Especially if the buyer in question is not well educated in the electronics field. Or for some its a status symbol and they want something to look as fancy and expensive as possible in their den/living room and I think that's a lot of what this is trying to appeal to. I've seen hifi units made out of polished copper and it is quite a stunning and beautiful look, but its damn expensive, and most likely offers no real advantage aside from cosmetics.
I work in the audiophile industry so I will say this. There are a lot of companies out there that make a lot of really fantastic sounding products. There are also a lot of people out there that have great ears and can appreciate the sound of these products. There also a lot of people who have lots of money and are looking for something fancy to spend it on. So you'll see a lot of products with flimsy justifications for added fancy-ness, and you can hardly blame them for it too. If you have two products all else being equal and someone wants to drop 100k on a stereo system, then the one with all the outlandish claims and fancy metalwork will probably win out. Especially if the buyer in question is not well educated in the electronics field. Or for some its a status symbol and they want something to look as fancy and expensive as possible in their den/living room and I think that's a lot of what this is trying to appeal to. I've seen hifi units made out of polished copper and it is quite a stunning and beautiful look, but its damn expensive, and most likely offers no real advantage aside from cosmetics.
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Stevem
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Re: Copper chassis ?
When you know what you are doing build wise and have enough chassis area then there is no need for anything better than a steel chassis!
For far far less then the massively added cost of a Copper chassis you can build a zero ripple high current DC heater supply for the amp and have a low enough noise floor for even medical equipment useage!!
For far far less then the massively added cost of a Copper chassis you can build a zero ripple high current DC heater supply for the amp and have a low enough noise floor for even medical equipment useage!!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Copper chassis ?
Copper is not magnetic. Copper is more conductive than aluminum, about 40%, but it's not only several times more expensive, but also denser, so for the same >conductivity< you need nearly twice as much >weight< of copper to get equivalent low resistance.
Steel "conducts" magnetic fields. Whether a steel chassis conducts AC hum and noise magnetically to the audio circuits depends a LOT on the layout and construction of the chassis and wiring (for example, loops of wire make magnetic pickups, and the bigger the area of the loop, the bigger the pickup).
There are situations where steel chassis can be a magnetic shield as well as a magnetic conductor.
The most highly regarded mike input transformers generally have multiple layers of shielding, alternating soft electrical iron and copper. The iron "shorts" the ambient magnetic field around the transformer inside, and the copper's high conductivity fences the ambient M-field out. Multiple layers of this cut the penetrating fields a lot.
Current flowing through a conductor also causes a magnetic field around it so you can also cause magnetic coupling by running currents through a wire loop, and have that picked up by another wire loop - we generally call these transformers, but nearby wire loops work fine as well.
Copper as a chassis material may help noise, cause more noise, or have no effect whatsoever. Likewise aluminum and steel. The details of how the chassis is laid out and how the circuits are wired often matter dramatically more.
As always, the devil is ALWAYS in the details.
Steel "conducts" magnetic fields. Whether a steel chassis conducts AC hum and noise magnetically to the audio circuits depends a LOT on the layout and construction of the chassis and wiring (for example, loops of wire make magnetic pickups, and the bigger the area of the loop, the bigger the pickup).
There are situations where steel chassis can be a magnetic shield as well as a magnetic conductor.
The most highly regarded mike input transformers generally have multiple layers of shielding, alternating soft electrical iron and copper. The iron "shorts" the ambient magnetic field around the transformer inside, and the copper's high conductivity fences the ambient M-field out. Multiple layers of this cut the penetrating fields a lot.
Current flowing through a conductor also causes a magnetic field around it so you can also cause magnetic coupling by running currents through a wire loop, and have that picked up by another wire loop - we generally call these transformers, but nearby wire loops work fine as well.
Copper as a chassis material may help noise, cause more noise, or have no effect whatsoever. Likewise aluminum and steel. The details of how the chassis is laid out and how the circuits are wired often matter dramatically more.
As always, the devil is ALWAYS in the details.
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pompeiisneaks
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Re: Copper chassis ?
Learn something new every day! Thanks, guess my assumption of copper and magnetism was out in left field
The info is great too, thanks!
~Phil
The info is great too, thanks!
~Phil
tUber Nerd!
Re: Copper chassis ?
This is in the same mumbo-jumbo league as some HiFi buffs claiming that a steel chassis will distort the sound.....
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Kagliostro
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Re: Copper chassis ?
On the past days Fender had something like a part of the chassis build with copper
the result is oxidation and gremlin problems after an adequate time
Some time ago I read about a guy who experimented with various materials as to solve a shielding problem in an amp
the winner material was aluminium, nor iron or steel or copper (may be he didn't had mumetal under hands to give a try)
K
the result is oxidation and gremlin problems after an adequate time
Some time ago I read about a guy who experimented with various materials as to solve a shielding problem in an amp
the winner material was aluminium, nor iron or steel or copper (may be he didn't had mumetal under hands to give a try)
K
Last edited by Kagliostro on Mon May 22, 2017 6:47 am, edited 1 time in total.
Re: Copper chassis ?
Again, the devil is always in the details.
I have no doubt that with one experimenter's efforts, the winner was aluminum. I also have no doubt that another experimenter, another layout, the winner would be steel. Or copper. Or copper plated steel. Or layers of each.
Layout matters, both of the magnetic components, and the conductive parts - wires.
And the parts involved matter. How much magnetic leakage did the experimenter's power transformer have? And how much sensitivity to surrounding M-field and E-field did the choke(s) and OT have? Which direction did the transformer's magnetic axes point? Was the PT an E-I lamination or a toroid? If the PT was EI-lams, did it have a belly band? Were the clamping bolts insulated from the laminations? How close to saturation was the transformer iron run on all three magnetic parts? Were the heater leads twisted pairs? Were the PT leads into the rectifiers twisted? What kind of rectifiers? How was the grounding of the chassis and first filter cap done? All of these things can have a big effect, as any experienced amp-builder can tell you.
I'm not trying to say that this guy was wrong about aluminum. It's just that electrical noise surrounds us. We live in a sea of it. For his setup, aluminum was best.
Humans do very well at dealing with systems that have a few variables. Beyond a few variables, they pattern recognize and guess. We pattern recognize so well that we see patterns in truly random things.
The best you can do is to learn the basics and keep an open mind. If you do this, you can optimize for one thing, then shift over and beat on another thing; then try a third, fourth, and so on. That can get you better results than any single optimization.
Here's another anecdote: Thomas Organ's Beatle amps had the power transformer sitting less than 3/8" from the bottom of the preamp chassis pan when the 3-D puzzle of all the parts was fit inside the enclosure. On the Beatle, but not on any of the same-chassis smaller amps, they found it necessary to add two rectangular plates, one of steel and one of thick aluminum, bolted to the chassis in the gap between the preamp and power transformer. Many repairers leave these plates out when reassembling the amp. The result is higher hum, even through the steel preamp chassis. Even more interesting, the ORDER of the two shield plates matters. It's quieter to put the steel plate closest to the PT, the aluminum plate closest to the preamp chassis when bolting the two plates back on. You apparently get more hum attenuation by letting the steel plate shunt as much of the midair M-field back into the steel chassis as it can, and the conductive aluminum plate's eddy-current and field effects push the remainder back into the steel.
I have no doubt that with one experimenter's efforts, the winner was aluminum. I also have no doubt that another experimenter, another layout, the winner would be steel. Or copper. Or copper plated steel. Or layers of each.
Layout matters, both of the magnetic components, and the conductive parts - wires.
And the parts involved matter. How much magnetic leakage did the experimenter's power transformer have? And how much sensitivity to surrounding M-field and E-field did the choke(s) and OT have? Which direction did the transformer's magnetic axes point? Was the PT an E-I lamination or a toroid? If the PT was EI-lams, did it have a belly band? Were the clamping bolts insulated from the laminations? How close to saturation was the transformer iron run on all three magnetic parts? Were the heater leads twisted pairs? Were the PT leads into the rectifiers twisted? What kind of rectifiers? How was the grounding of the chassis and first filter cap done? All of these things can have a big effect, as any experienced amp-builder can tell you.
I'm not trying to say that this guy was wrong about aluminum. It's just that electrical noise surrounds us. We live in a sea of it. For his setup, aluminum was best.
Humans do very well at dealing with systems that have a few variables. Beyond a few variables, they pattern recognize and guess. We pattern recognize so well that we see patterns in truly random things.
The best you can do is to learn the basics and keep an open mind. If you do this, you can optimize for one thing, then shift over and beat on another thing; then try a third, fourth, and so on. That can get you better results than any single optimization.
Here's another anecdote: Thomas Organ's Beatle amps had the power transformer sitting less than 3/8" from the bottom of the preamp chassis pan when the 3-D puzzle of all the parts was fit inside the enclosure. On the Beatle, but not on any of the same-chassis smaller amps, they found it necessary to add two rectangular plates, one of steel and one of thick aluminum, bolted to the chassis in the gap between the preamp and power transformer. Many repairers leave these plates out when reassembling the amp. The result is higher hum, even through the steel preamp chassis. Even more interesting, the ORDER of the two shield plates matters. It's quieter to put the steel plate closest to the PT, the aluminum plate closest to the preamp chassis when bolting the two plates back on. You apparently get more hum attenuation by letting the steel plate shunt as much of the midair M-field back into the steel chassis as it can, and the conductive aluminum plate's eddy-current and field effects push the remainder back into the steel.
Re: Copper chassis ?
I can think of one advantage: Copper is an excellent conductor due to its low resistance so if you abandon all decent grounding layouts and schemes, and just connect the grounds to closest convenient place in the chassis using the whole chassis as "ground terminal", the ground return currents will introduce lower voltage voltage drops and lower interference overall due to that.
It works decently as long as the copper does not oxidize at contact points, which will likely happen eventually, after, which its of course "noise city"....
Irony in all this is that its the poor ground routing in the first place that will introduce most of the interference.
Personally, instead of using multiple "random" ground points all over the chassis I would rather follow some decent ground routing scheme to minimize all ground noises from the start. Then you likely need just one or two ground reference points tied to the chassis. When the ground currents actually return where you want them to return the tiny resistance of the ground path becomes no concern.
As said, for overall "shielding" you find steel more useful.
It works decently as long as the copper does not oxidize at contact points, which will likely happen eventually, after, which its of course "noise city"....
Irony in all this is that its the poor ground routing in the first place that will introduce most of the interference.
Personally, instead of using multiple "random" ground points all over the chassis I would rather follow some decent ground routing scheme to minimize all ground noises from the start. Then you likely need just one or two ground reference points tied to the chassis. When the ground currents actually return where you want them to return the tiny resistance of the ground path becomes no concern.
As said, for overall "shielding" you find steel more useful.
Re: Copper chassis ?
Is copper magnetic ?
answered here;
http://terpconnect.umd.edu/~wbreslyn/ch ... netic.html
materials used in an amp that does not operate on a 'plane' interact in ways that would make a wise study
answered here;
http://terpconnect.umd.edu/~wbreslyn/ch ... netic.html
materials used in an amp that does not operate on a 'plane' interact in ways that would make a wise study
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Kagliostro
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Re: Copper chassis ?
WOW !
Very interesting
K
Very interesting
K
Re: Copper chassis ?
Steel is ferrous and can develop eddy currents with the tranny(s) so it may cause some sort of 'distortion' or coloration to the signal.
It's true i've lost my marbles and i cant remember where i put them
Re: Copper chassis ?
Yeah, HI-Fi buffs see distortion or 'potential' for distortions like a vampire seeing sunlight at dawn.
A great mindset is to realize guitar amp builders use distortions and sonic influence as design parameters. Now, for a sample of this , remember your chassis is a shield, a structure to house the components, and also a ground. Some call it a ground plane , but its not a plane , its a 3-d build. Now that we recognize a 3-d build, think in 3-d design. First thing that becomes an easy examply is whats happening with those giant iron transformers eh? tic toc tic toc ..... ding ding . Oh shit ,they irradiate an electromagnetic torroid ball of energy Everywhere
ugh, now what? he , he 
A great mindset is to realize guitar amp builders use distortions and sonic influence as design parameters. Now, for a sample of this , remember your chassis is a shield, a structure to house the components, and also a ground. Some call it a ground plane , but its not a plane , its a 3-d build. Now that we recognize a 3-d build, think in 3-d design. First thing that becomes an easy examply is whats happening with those giant iron transformers eh? tic toc tic toc ..... ding ding . Oh shit ,they irradiate an electromagnetic torroid ball of energy Everywhere
ugh, now what? he , he Re: Copper chassis ?
Good article, gets to the second level of magnetic interactions, the electromagnetic and eddy current effects of a non-ferromagnetic metal moving inside a magnetic field.
There is a caveat that the article missed. Pennies are not pure copper, nor even a mostly copper alloy. Up until 1982, USA pennies were an alloy containing about 95% copper, the rest included to make them more durable. In 1982, the USA switched over to a zinc penny that is copper plated. Pennies have been copper plated zinc for about 35 years.
Of course, that doesn't matter much as zinc is about the same amount ferromagnetic as copper - which is to say, essentially NOT. It's not as good a conductor, but then the conductive effects aren't magnetic effects.