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Best chassis material? Steel or Alum.


 
4/20/1999 9:01 AM
RJH
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Best chassis material? Steel or Alum.
I'm going to start another DYI. I plan to purchase one of the Hammond prefab chassis. Which will make a better all round amp -- Steel or Alum.. I would imagine that the Alum. chassis would be easer to work with. However, a steel one would offer its magnetic properties as a shield. Opinions/Flames Thanks RJH
 
4/20/1999 1:55 PM
R.G.
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Aluminum is 1/3 the equivalent strength and weight of same-size steel, and 3 times the price. It's *much* easier to work, and is better shielding against radiated E-fields and high frequency M-fields like RFI.  
 
Steel is far stronger, and harder to work, and is better for shielding from low frequency magnetic fields. It is also ferromagnetic, and can "conduct" AC hum into places it wouldn't otherwise go from the power transformer and choke.  
 
Which is all round better? Define "better"...  
 
It mostly depends on your skills and available tools, not the ultimate performance of the chassis. "Best" is probably a congolmerate, steel for the overall chassis and transformer support, and an aluminum section for the input and high gain parts. Not too practical, but better for hum, noise, and shielding.  
 
I've seen a solid *copper* chassis on an ultra hifi setup, which also used solid teflon circuit boards...
 
4/20/1999 4:44 PM
RJH
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R.G.  
 
Thanks for the post! My idea was to use a 17 X 10 X 2 alum. chassis from Hammond I've seen them for under $25. I was going to us it in a "tube up" Marshall like head. I'm a fairly good metal worker and a damn good woodworker/tolex coverer. I'm going to use some Tax refund $$$ and get some Greelee punches 1 for 9 pin the other for 8 pin. Can you suggest the appropiate size punches? Anyway, this will not be a heavy transformer amp. I've got a Hammond 1608 on hand so I do something pp el84s this would also dictate a lighter weight power xformer. My main concern with the two types was their hum/noise rejection. From your post it would seem that alum. has some advantage in rejecting AC type interference. Does that translate to reduced high freq ossolation? Anyway, a big thanks to you and all who have responed to my rash of questions -- its amazing how much I've learned here at AMPAGE!! RJH
 
4/20/1999 4:56 PM
Ken Gilbert
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quote:
"I'm going to use some Tax refund $$$ and get some Greelee punches 1 for 9 pin the other for 8 pin. Can you suggest the appropiate size "
 
 
I just thought I'd chime in here and point out that although most 9 pins fit in a 3/4" hole, the ceramic sockets will NOT. All of the ceramics I've use demand a hole of about 7/8".  
 
Hell, I don't even OWN a 3/4" punch!  
 
I've also found that pannel mount XLR jacks take a hole a HAIR bigger than 3/4", so they can be handy there too. (Balanced interconnects RULE!)  
 
As for the octals, I use a 1+1/8. It also comes in handy for LCR can caps. Just be sure when you mount them there's a good 1/4" of air between the chassis and the terminal lugs of those caps!  
 
Am I the only one who uses all ceramic sockets? They ARE quieter, ya know. You won't find a plastic socket for a mic input stage! Well, unless it was cheap... ;-)  
 
 
~KG~
 
4/20/1999 8:44 PM
Bruce
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quote:
"Am I the only one who uses all ceramic sockets? They ARE quieter, ya know. You won't find a plastic socket for a mic input stage! Well, unless it was cheap... ;-)"
No, just the only one still who brags about it. :>)  
 
As for the Fe vs Al chassis.. save yourself some grief for the first few amps and use nothing but aluminum.  
Get a chip chaser and a 3/4" unibit too.  
 
Bruce
 
4/20/1999 11:35 PM
Brian
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I have worked with both steel and aluminum chassis. I don't get the fact that aluminum is easier to work with. I have problems when drilling larger holes (3/8-1/2") with the drill bit making rounded triangular cuts. This makes it hard to mount things properly and nice looking. I would go with steel, it drills harder but much nicer, and if you have punches then they will take the steel no problem. Al looks nicer on the face though.  
 
Brian
 
4/21/1999 12:35 AM
Doug
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9 pin ceramic takes 7/8", I used a 1" for my octals. I used spade bits for the smaller holes in my aluminum chassis. I had the same problem with the twist bits in aluminum making the funky holes, almost had to scrap my chassis. I used metal hole saws for the tube sockets, touched up with wire brush on a dremel. Worked real nice.  
Doug
 
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