Aluminium vs steel chassis - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th June 2007, 12:30 PM   #1
diyAudio Member
 
Rob11966's Avatar
 
Join Date: Jun 2007
Location: Australia
Default Aluminium vs steel chassis

Hi,
As mentioned in an earlier post I am building my first power amplifier from scratch. I have decided upon the Dynaco St70 (availability of parts, relitive simplicty of construction + wanted to build a stero unit) but I am setting up my own layout and design. So far I have built a cardboard mock-up and I am about to take it to a sheet metal worker.
Here's the question - according to Morgan Jones, 'steel is not suitable for valve amplifiers'. Is this an absolute rule or is steel OK provided that the transformers are mounted with something between them and the chassis.
Cheers,
Rob
  Reply With Quote
Old 19th June 2007, 02:11 PM   #2
diyAudio Member
 
sorenj07's Avatar
 
Join Date: May 2006
Steel is bad. .1" aluminum is good.
  Reply With Quote
Old 19th June 2007, 02:26 PM   #3
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally posted by sorenj07
Steel is bad. .1" aluminum is good.

Why, please?
  Reply With Quote
Old 19th June 2007, 02:34 PM   #4
diyAudio Member
 
p_ete2003's Avatar
 
Join Date: Nov 2003
Location: Helsinki
I've used both and aluminum is a lot easier to work with.
  Reply With Quote
Old 19th June 2007, 03:01 PM   #5
diyAudio Member
 
zigzagflux's Avatar
 
Join Date: Oct 2006
Location: Charlotte, NC
I use steel. I like the magnetic shielding it provides from the transformers and chokes above. You could have eddy currents in said chassis, but the field is still shielded from the signals below.

I would think it important to electrically isolate the transformers mounted on it. I use rubber washers (with the additional vibration control) with teflon shoulder washers. Each device then gets bonded to chassis in one point. This avoids circulating currents.

I'm not sure why Jones said this, though there may be some context to it that we're missing. If it has to do with induction, there are usually procedures and installation methods that avoid or minimize it.

Ease of installation has nothing to do with the choice, in my book. My punches and drills go through both Al and steel.
  Reply With Quote
Old 19th June 2007, 03:07 PM   #6
nhuwar is offline nhuwar  United States
diyAudio Member
 
nhuwar's Avatar
 
Join Date: Jan 2007
Location: Cypress Texas
Steel chassis can effect inductors. It can get magnetized which is bad. And yes it's alot harder to work then aluminium.

Nick
  Reply With Quote
Old 19th June 2007, 03:17 PM   #7
zlast is offline zlast  United States
diyAudio Member
 
Join Date: Sep 2004
Location: none
Send a message via AIM to zlast Send a message via MSN to zlast Send a message via Yahoo to zlast
Default Steel vs Aliminum

Steel is stronger and cheaper.

Consider your final product...are you planning on painting or some other method of finishing? Aluminum can be left unfinished and look great, steel needs some sort of protection to keep from rusting. Also consider HOW your chassis is going to be assembled, nuts,bolts,rivets,welded,screws - this might influence the material you use - and the gauge. You may want to discuss these points (and cost) with whomever you hire to build the chassis...
__________________
none
  Reply With Quote
Old 19th June 2007, 03:45 PM   #8
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
The notion of circulating currents in a steel plate is valid. I am not sure about how strong a field would be required to induce such a field, or how easy it would be for that field to couple on to other components.

Steel would provide superior shielding, whereas aluminium would provide no opportunity for inductively derived circulating currents, and be physically easier to work.

Humm, an interesting choice...
  Reply With Quote
Old 19th June 2007, 04:40 PM   #9
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
I have wrecked more than a couple of punches on steel chassis obviating any savings in cost between the two.

Aluminum is a much better thermal conductor that steel, and this helps when using the chassis as a heatsink for regulators and power resistors.

Steel is a better magnetic shield, but is no more effective against electrostatic fields.

Steel is stiffer and stronger when heavy weights are an issue.

Steel rusts, aluminum doesn't.

Steel is a little easier to paint, that said I have aluminum chassis painted a decade ago with no issues.

Hammond sells aluminum chassis that are pre-primed and easy to paint.

Some people allege that a given circuit sounds better in a non magnetic chassis as opposed to steel - perhaps this due to magnetic fields in conductors interacting with the chassis. (aka increased parasitic inductance.)

HH Scott used AL chassis for both thermal and sonic reasons based on the comments made by former employees. (And some of their literature as well.)

With careful design either material ought to be fine, AL is generally easier for the typical diyer to handle with simple hand tools.

I like copper even better, but it's too expensive, really hard to work because of it's softness, (Clogs drill bits, end mills, punches, etc), greater thickness is required for a given load on the top plate, needs to be well protected from oxidization, and is prone to bending and scratching. However nothing looks better than clear coated copper IMHO..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 19th June 2007, 04:54 PM   #10
nhuwar is offline nhuwar  United States
diyAudio Member
 
nhuwar's Avatar
 
Join Date: Jan 2007
Location: Cypress Texas
I have always been parshall to silver plated copper then clear coated It looks good. But stainless would do a good job as long as you dont bend it or work it to much as 300 seires becomes magnetic from cold working. It could feasably polished to a mirror finish for a top plate for a amp.

Nick
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
DIY Steel Chassis GlidingDutchman Everything Else 4 2nd August 2008 07:11 AM
aluminium and steel sheeting thickness? VvvvvV Parts 2 1st April 2007 12:54 PM
How to paint al/steel chassis? protos Parts 14 18th May 2006 11:03 AM
Extruded Aluminium Chassis fireman Chip Amps 7 1st June 2004 03:13 PM
Aluminium chassis finishing FrankDIY Everything Else 0 21st August 2002 11:35 AM


New To Site? Need Help?

All times are GMT. The time now is 11:53 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2