In my sole completed amp, I epoxied a sheet of copper to an aluminum sheet. The thicker aluminum adds the stiffness as thick copper would be way too expensive. The epoxy provides the barrier so the two metals don't react in the presences of moisture.
To throw my $.02 in.
I have used aluminum and steel prefab chassis and found that aluminum is by far easier for cutting, drilling and punching.
There are lots of other chassis materials though.
One method I used recently and will continue to use in the future is using a "hybrid" chassis.
I use hardwood (cherry, oak etc) to build a "box" (four sides) using a router (not network but wood router LOL) I mill a rabbet on the top and bottom edges to accept a piece of veneered plywood for the top and bottom plates.
I layout the location of all of the holes for sockets, caps, trannys etc on the bottom unfinished side of the plywood in pencil (allows erasing the inevitable mistakes)
I use Copper Clad PC board in multiple pieces for each section of the amp.
ie; one larger piece for the amplifier section, smaller ones for the power supply and input/volume/tone controls.
I "laminate" these pieces with elmers glue to the "finished" side of the plywood. I then use a small 1/8" drill bit to mark all the hole centers etc.
Once all the centers have been made I separate the PC board and plywood. I can then finish the wood and PC board holes etc separately. By making the holes in the wood "oversized" the tubes fit nicely and look more "finished".
The copper clad board provides a nice "Ground Plane" and allows me to work with the circuit section individually making it much easier to do.
Once the circuit is relatively complete I then completely finish the top plate and glue it into the frame. A couple coats of urethane and it's good to go.
I use epoxy and the transformer and can cap machine screws to adhere the PC board to the underside of the plywood. Judicious use of the epoxy allows the board to be carefully removed in the future for modifications.
Here are some old photos of two amps built this way. (bottom plates removed)
http://www.facebook.com/album.php?aid=15890&id=1456476805&l=ba8e249421
I have used aluminum and steel prefab chassis and found that aluminum is by far easier for cutting, drilling and punching.
There are lots of other chassis materials though.
One method I used recently and will continue to use in the future is using a "hybrid" chassis.
I use hardwood (cherry, oak etc) to build a "box" (four sides) using a router (not network but wood router LOL) I mill a rabbet on the top and bottom edges to accept a piece of veneered plywood for the top and bottom plates.
I layout the location of all of the holes for sockets, caps, trannys etc on the bottom unfinished side of the plywood in pencil (allows erasing the inevitable mistakes)
I use Copper Clad PC board in multiple pieces for each section of the amp.
ie; one larger piece for the amplifier section, smaller ones for the power supply and input/volume/tone controls.
I "laminate" these pieces with elmers glue to the "finished" side of the plywood. I then use a small 1/8" drill bit to mark all the hole centers etc.
Once all the centers have been made I separate the PC board and plywood. I can then finish the wood and PC board holes etc separately. By making the holes in the wood "oversized" the tubes fit nicely and look more "finished".
The copper clad board provides a nice "Ground Plane" and allows me to work with the circuit section individually making it much easier to do.
Once the circuit is relatively complete I then completely finish the top plate and glue it into the frame. A couple coats of urethane and it's good to go.
I use epoxy and the transformer and can cap machine screws to adhere the PC board to the underside of the plywood. Judicious use of the epoxy allows the board to be carefully removed in the future for modifications.
Here are some old photos of two amps built this way. (bottom plates removed)
http://www.facebook.com/album.php?aid=15890&id=1456476805&l=ba8e249421
I will measure it for you the next time.
It is soft enough, but still springy.
I use couple of 17" long peaces of a steel angle to bend it. A first, I bend shorter sides, then 17" ones.
Copper's good but you put a little zinc in it,,,,,, and big trouble.
And class do we remember what you get when you add a little zinc to copper.
Thats right BRASS.. Brass is not the best thing to use. It's will sing like Celine Dionne LOL
I was not trying to offend anyone with the wording there just trying to be funny.
In retrospect all brasses don't sing or resonate, Just most of them.
Nick
P.S. If you want to go all out and you have tons of money tungsten is the way to go. Especially if you use a tungsten powder in a rubber matrix and bond it to any metal. Thats crap will dampen even the strongest vibrations.
But thats a tad bit overkill for our apps.
I use aluminum or Lexan for the top plate because they are easy to work with. I usually make the sides out of wood. The quick and easy way is to use a pre-formed Hammond chassis. Yes all of these materials (especially the Hammond chassis) can exhibit mechanical resonances. How do you deal with that? You can actually learn something from that kid down the street with the thumpa - thumpa car. Dynamat, Fatmat, or any one of a dozen other names. It is a polymer based material with adhesive on one side. Some versions have a thick aluminum foil on the other side (ground it). If it can keep the car trunk from booming with a 1.21 Gigawatt subwoofer inside, it can tame a chassis or top plate.
Hi Diy
I like using 2mm copper plate and steel ,copper can be a pain to work with all drill bits need to be cut at different angles .
This is a picture of my dac ,one day a cover will be made and the steel base nickel coated.
Making some amps up latter this year and they will be copper ,steal and #8 polished stainless .
One thing my mate has the same digital circuit dac with a different power supply all in timber but has a higher floor noise the the steel & copper chassis.
Cheers
I like using 2mm copper plate and steel ,copper can be a pain to work with all drill bits need to be cut at different angles .
This is a picture of my dac ,one day a cover will be made and the steel base nickel coated.
Making some amps up latter this year and they will be copper ,steal and #8 polished stainless .
One thing my mate has the same digital circuit dac with a different power supply all in timber but has a higher floor noise the the steel & copper chassis.
Cheers
Well, I'm surprised at the number of responses I've seen. Thanks to all.
A friend has offered to make a walnut box to match my Klipsch Hearse speakers (Black lacquer Walnut) to which I will add 0.130" thick aluminum sheet on which to build the amp(s).
Since I have the aluminum sheet, and free labor on the wood work I guess I'll go that way.
I had considered Hammond Al or Fe chassis as a second choice.
I'll use Hammond 1609 transformers with selectable UL/standard output to compare them.
Now if only my 6P1P-EV tubes would arrive.....
Thanks all.
Steven
A friend has offered to make a walnut box to match my Klipsch Hearse speakers (Black lacquer Walnut) to which I will add 0.130" thick aluminum sheet on which to build the amp(s).
Since I have the aluminum sheet, and free labor on the wood work I guess I'll go that way.
I had considered Hammond Al or Fe chassis as a second choice.
I'll use Hammond 1609 transformers with selectable UL/standard output to compare them.
Now if only my 6P1P-EV tubes would arrive.....
Thanks all.
Steven
It works just like a bell or a guitar string. For instants if you where to make a bell out of something other then bell brass. And you struck that said bell. Instead of a nice ringing sound you would get a high pitch thud sound.
Dampening is part of it but it's not what I'm talking about here.
Nick
Thx Nick. In my experience 1/4" EMT steel tube couldn't be tamed by the extreme measure of polyurethane gluing a 1/8" aluminum sheet damped with mineral tile to the back surface whereas two 3/16" aluminum plates freely laid on each other without damping sound like granite under the knuckle test. Gots ta go wit wut I know.
Not to put too fine a point on it, but a knuckle rap is no kind of scientific test as to whether a chassis material's oscillation will exacerbate microphony or otherwise contribute in a negative way to the noise floor. Although noise from a material that has a low damping capacity (like steel or aluminum) may seem to dissipate quickly, inaudible but significant oscillation will continue for some time.
John
John
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Ya you use accelerometers and a repeatable method of excitation. And you look at the output of the accelerometer on a spectrum analyzer.
You have me at loss on that one. While obviously just hitting something isn't scientifically rigorous, why is it worthless? Simple mechanical excitation says nothing of value about a material's resonances? I fully understand the final result must take into account the susceptibility and frequencies of the devices mounted on the chassis.
Sorry agent.5, I meant it as an metaphor; dead as a block of granite. If I recall correctly sheet stone is still more resonant than two bonded aluminum plates. The advantages of using the latter instead are just too numerous though I have considered stone bonded to aluminum for the aesthetics.
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