steel chassis vs aluminum chassis

[blues man]

I read an article in The Ultimate Tone by Kevin O'Conner on using metal screening to shield around the transformers and tubes in a head which would be very hard to do in a combo amp. He says use steel not aluminum because aluminum does not confine stray magnetic fields. Which brings me to the question which is better, steel or aluminum chassis's or does it matter. I would think that steel would be better for repelling magnetic waves from entering the chassis. Your thoughts?

[PRR]

> does it matter

Al is easier to drill.

Iron may stand more road-abuse.

[kagliostro]

In steel chassis the magnetic flux has an open door to propagate, aluminium, for this aspect of the problem, is better, also is more easy workable

as to build a shield iron is better than aluminium and stainless steel (because those are nonmagnetic metals)

sometime ago there was, here into the forum, a large discussion about chassis materials

Kagliostro

[Bub]

Not to highjack this post but I've wondered if the metal cage around tubes like on the Ampeg B15 stops any interference or magnetic fields from affecting the tubes provided the cage is grounded.

Thanks

Rob

[Fresh_Start]

"road abuse" as PRR points out may dictate a steel chassis, especially if you have relatively heavy transformers.

Not to highjack this post but I've wondered if the metal cage around tubes like on the Ampeg B15 stops any interference or magnetic fields from affecting the tubes provided the cage is grounded.

Thanks

Rob

According to the 12AX7 data sheet the shield affects the internal capacitance of the tube.

I've done un-scientific tests with both steel and aluminum shields and didn't hear any noticeable noise reduction.  However, there weren't any flourescent lights or radio towers nearby...

HTH

Chip

[Leevi]

I have built amps by using both Aluminum and Steel chassis and have not noticed any differences
what comes to magnetic issues. But as already mentioned here the Aluminum is easier to machine and
it is lighter. Furthermore I would consider the better electrical conductivity of Aluminum important
since it can probably prevent ground loops better than a steel chassis.
/Leevi

[blues man]

Thanks for the input from all of you. I value the opinions I read here. I personaly like punching my own chassis. I'll have to consider aluminum.

[Platefire]

I guess I'm old school, no paticular reason for but I've been buying steel. Platefire

[LooseChange]

I use Hammond steel blank chassis for all my new builds.

[ThermionicEngine]

As noted in most of the replies, I have worked with both materials and seen the benefits and drawbacks to each.  I could not scientifically tell which one was quieter as the circuits were very different.  I will note that I wish I could solder to Aluminum...
Cheers,
Larry

[kagliostro]

I will note that I wish I could solder to Aluminum...

I don't know the name of the metal league, but sometime I've seen (at Ham Fest) some spools of wire

that can be used to solder to alluminium using a standard soldering iron to tin

Kagliostro

[jojokeo]

Why solder to aluminum OR steel?!? Poor choice for long term grounds. Use solder lugs and serrated washers or serrated lugs. Sercure it at one place usually a tranny bolt or single point location very tightly w/ thread lock or lock nut and it's good to go for decades. Depending on solder joints to chassis', pots, and other multple places is asking for trouble sooner or later.

*I like aluminum compared to steel as steel has a propernsity for corrosion, magentic property issues, harder to fabricate, harder on tools, adds more weight, doesn't dissipate heat as well, not as good a conductor, more costly (due to some of these issues), more time consuming to fabricate, etc.

[bluesbear]

"Why solder to aluminum OR steel?!?"

I agree. I never solder to the chassis. I'll crimp and solder wire to a ring terminal, then bolt it to the chassis. It just seems more permanent to me. Indestructable is the goal. My hero for build quality is Pete Traynor. He threw them of the roof to test the build quality. That's a REAL test!
Dave

[phsyconoodler]

Traynor amps are the worst rats nest I've ever seen.And he was a HUGE fan of soldering to the chassis.I find that the solder on the chassis is much better than a bolt and nut.Nothing to come loose,break or corrode.
  Some of the simpler Traynor amps he did very early on were nice inside,but most are awful.I see LOTs of vintage Traynor amps here in Calgary.

But.......they are tough as nails.The cabinets were way overbuilt which really helped them in road-worthiness.

[navdave]

Are they pretty strong? Been wanting to try one but I like building 100 watt amps or greater so Ive shied away from them so far.

I use Hammond steel blank chassis for all my new builds.

[ThermionicEngine]

Duly spanked  :embarrassed:but clearly I don't solder to an aluminum chassis, I use the Keps-nut-and-lug-on-the-tranny-bolt.  On steel I get an 80 Watt iron with a 3/8 chisel bit and I make a main ground point with a dime sized (maybe a bit smaller) solder joint. My ground buss wire, center taps and miscellaneous ground wires go there.  I do attach the earth ground to a transformer bolt.  I do use steel for Fendery types and Aluminium for British.  My magnum opus was done in an Aluminum chassis.
Cheers,
Larry

[overtone]

Some day I would like to have a stainless steel chassis made up. I think Cornell does that.

On ground points:
There is something about the road life of an amp that stresses those transformer bolts and seems to make them want to loosen up. On quite a few older amps that I have seen they were loose and in one case the earth ground had drifted off altogether. Toothed and locking nuts may help, but recently I picked up a tip for an SE amp: move the ground point away from the PT to reduce noise issues. Food for thought.

[LooseChange]

Are they pretty strong? Been wanting to try one but I like building 100 watt amps or greater so Ive shied away from them so far.

I use Hammond steel blank chassis for all my new builds.

I don't know how well you can see it... But down at the bottom of the picture is a reinforcing rod for a 180w Orange Bass amp rebuild. It's a piece of 1/2" x maybe an 1/8" steel band. Captured under the PT and OT bolts.

I always add a separate bolt for earth andf ground to the chassis. I dremel the surface a bit first. When I remember I use lock tight on the tranny bolts.

[overtone]

Thanks for the photo, is this an Orange chassis or the Hammond steel chassis for the rebuild?

The flimsiness of a Hammond "heavy duty" aluminium chassis really shocked me, so I had a 5mm aluminium plate cut for the top to carry the transformers.

On some of my larger british amps, where the weight of the Partridge transformers has distorted the steel over time, I now add reinforcements. Sometimes there is only space for larger washers, but it helps a little towards keeping them roadworthy.
Best, tony

[bluesbear]

"Traynor amps are the worst rats nest I've ever seen."

I'm certainly not talking about the crap they make now, only when Pete was in charge. However he did it, they were NOT fragile! I don't consider the modern stuff to be real Traynors, any more than I do modern Fenders and Marshalls.
Dave

[tubeswell]

'nother vote for ally (especially when you acquire your own folding brake capable of doing easy bends in 2mm ally).

[Willabe]

'nother vote for ally (especially when you acquire your own folding brake capable of doing easy bends in 2mm ally).

Oh man, you got your own brake? Nice, I wish I had one. Always need more tools!

        Brad       

[tubeswell]

I started with doing it by hand with a hunk of 4 x 2 and brute strength and a hammer. This achieved a workable solution with if you were cunning about where you hammered it, you could keep those parts hidden.

Then I made my own home-made brake out of $35 worth of scrap metal, but the hinges gave out in quick order.

So I finally relented and splashed out on this fancy gizmo, and bending the metal has never been more thoroughly enjoyable

[blues man]

I am definetly going to try the hammond chassis for my next build. The price is right. The 2 bassman chassis that I have used were both twisted which made the back pnl not fit right. I was on webers site and I see he is not chrome dipping his chassis any more. I always wondered if chroming them caused the twisting from the heat or if it was just lousy craftsmanship.

[Willabe]

Very nice tubeswell.       


             Brad         

[Willabe]

blues man,

Try looking at--      dirty dawg amps.com         just another source for blank chassis. I have'nt bought one yet but I intend to soon.


             Brad           

[phsyconoodler]

Hammond chassis are really thin.Not a great idea.Go to an aluminum fabricating shop and get the chassis made for you.For an extra 15.00 they will punch all the holes for you if you supply a cad drawing.I do not use less than .080" thickness with aluminum.And I always get the ends welded unless I mount the chassis upright and use wings for mounting inside the cabinet.

[blues man]

I live in Naples fl and everthing here is priced like you have money to blow. I checked out an aluminum shop and they said at least $80 or &90 for one chassis with no holes. No thanks. I checked out dirty dawg from willabe's post (thanks for the tip). A chassis 19"x8"x2" for $15 and plate for $5, Now thats what I'm talking about.

[Willabe]

He'll weld the corners too, $5 more, and he's got .080" aluminum.


               Brad         

[John]

I bought 2 from dirtydawg (one extra in case I mess up) and they seem very solid.