18Watt.com

Hi,

I'm going crazy here deciding on material for chassis that I want to produce.

I did one in 1.5mm aluminum, and it was flimsy. Paul Ruby gave great advice on use of alum alloy. But I am having problems with my alum vendor, and the people at CNC place doesnt know much. Scared alum alloy I choose to crack or weak when bent, even with 2mm (0.08) alum.

So, I am contemplating of doing Ceria Tone chassis using CRS (similar to what Weber uses for their Fender chassis). It will be close ended because i feel open ended chassis is too flimsy. I dont think heat issues arise..

CRS will be a lot stronger. I really dont want to hear complaints of dents, etc, as well as durability issues, even years from now..

The chassis will be finished in either colors (candidates are gold, ferrari red, blue, etc), or chromed.


What do you guys think? It wont be original, but prices will be great (actually the cost of unfinished alum and finished CRS will be about same). I dont think sound will detract that much (if any?), but not sure about argument that alum will be quieter.

Any advice is appreciated.

Thanks!

Nik

PS - Production and one off are different beasts!

Nik, what's CRS? What thikness are you using? Will the corners be welded or not? And why is life full of so many questions?

Hey Nik,

I see you everywhere!

As long as it's somewhat sturdy and the holes are drilled correctly, I'm not worried at all. Many of the old Marshalls I've seen are kind of flimsy, maybe it's just age, but I could bend them with my hands if I wanted to.

I think you're on the right track! I personall would prefer just a polished or brushed finish, no colors.

All the best my friend!

Hi,

Hm...that's weird. I replied to Phil, but it isnt there.

CRS is Cold Rolled Steel. I plan to use 1.5mm, and it's welded at the ends.

Instead of separate pieces for ends, the chassis is gonna be from 1 whole piece, ie bent like a box.

1.5mm is really good enuff. This material is pretty good. Not sure how the response gonna be tho, because the original used alum.

Right now I have made decision 6 times already, alternating between the two. Life is many questions, this chassis thing sure add more...

Dan, latest new (today) is I might get something from alum, 2mm thick, with the nice looking (brushed?) and scratch proof surface. Price is high, tho for quality alum. I might have to sell the completed chassis for 50 bucks! Ouch... and that's not with face plate...

We'll see.

Nik

Hi Nik,

Great to hear you're working on chassis design. Since it sounds like you're looking for opinions, I'll chime in.

First, I'm not sure what you have in mind for sizes, are you planning to offer a number of different sized chassis, customized, or both? I'd be most interested in a good small head-sized chassis, 18"-20" by about 6.5".

I don't know anything about CRS, but if it's as sturdy and easy to drill as 2mm aluminum it should be just fine. Colors? Not really interesting to me, but a polished surface might be something I'd like. Even then, as a budget-minded DIYer I doubt I'd pay extra for it. I also like open-ended chassis since they're easier to work in, but rigidity is more important.

Keep up the good work Nik, I'm looking forward to seeing what you come up with.

Hey there Ric,

Thanks much for the encouragement and nice words!

CRS is what Weber uses for their Fender style chassis. The stuff is pretty strong, no complaints, but needs to be finished, which is another hassle, altho doesnt cost that much.

I decided if I use alum, it should be nice, and sturdy. So right now I chose the brushed type, and supposedly "scratch proof". Or maybe the vendor is just saying that? 2mm (0.08") thickness.

Which brings me to your point of open ended design. I agree it'd be easier to work with. I think it would be sturdy with added thickness, but still I decided to use close ended for assurance. But open ended would be original, and to me, it'd be less cost, translating to lower prices...

Hmm..decisions decisions. I have till Tuesday (gotta decide at one point) Maybe I'll flip coins.

Thanks!

Nik

Steel is the best. Don't mess with aly. Use what Marshall do. With steel ground connections are less prone to deterioration through oxidisation. The steel also helps provide a bit of magnetic shielding that aly doesn't, due to the way that the magnetic fields from the Xformers create eddy currents in the steel, which tend to be absorbed by the slightly higher natural resistance of the metal.

Hey Nik,

I'm sort of going with the crowd here. I would prefer open ended definitely. As far as material, I really don't care. Some people claim that Marshall used Aluminum or "Aluminium" as they say in Britain. I don't really know and don't really care. As long as it looks right and fits in the cabinet well, it's perfect to me! I can't imagine that material makes any difference in sound? That's all I care about.

I know you've mentioned that you can do the steel ones siginficantly cheaper than aluminum . . . I say go for it!

Phil - are you saying that Marshall used Steel? I don't know . . . I've never actually touched a real 18 watter. I know there a few 18 watt amp manufacturers who make selling point out of the Aluminum chassis as being original. Have you seen otherwise?

All the best guys!

I don't claim to have encyclopaedic knowledege of Marshall amps, like a lot of other folks seem to have. Just all the Marshall chasses I've ever come across have been steel, and I am under the impression that steel is their prefered choice.

Yes, I have seen some amp builders making fanciful claims for aly, but with little basis in physics. It is a fact that steel does help attenuate magnetic fields, due to the eddy currents that get set up within it at the same time as it's internal magnetic domains are being driven around the B-H curve. Where I'm sitting right now, there is some kind of huge electrical plant above the ceiling which used to emit a magentic field so strong that it made all the PC screens look 'wavy'. They put in a one-inch thick plate of steel underneath, and all the interference went away.

There is however, one important benefit to aly - it's easier to work with, drill, punch, etc! So DIY builders may still prefer it.

Ideally, it should be possible to completely enclose any chassis underneath, to block out RF interference from inside the amp - like from light dimmers, fluorescent lights, and local radio station. Open ended is fine, as long as you can close it up, when you've finished working on it.

The early JTM45s were made of aluminum and the 18W was aluminum as well. I saw a real 2-12 18W over the weekend and saw his aluminum chassis up close.
http://www.gdsamps.com/Photo/Judd18W/Ju ... 001med.jpg
http://www.gdsamps.com/Photo/Judd18W/Ju ... 003med.jpg

Enjoy!

That's very interesting. I must say that I haven't had the opportunity to inspect any Marshall amps, older than around 1970. My guess is that sometime in the late '60s and early '70s they switched to steel. I wonder if anyone else out there has more precise information...

Heya,

The first batch is going to be aluminum. I was in the area, and went to get some this afternoon. Won't fit in my car, so I took a chunk off to do, so I will have pics soon.

Extra features:

1. 2mm alum 5005.

2. Cater to both vintage style board, and standard modern boards(have mounting holes for both). Thanks Gab!

3. Open ended, but with holes to attach cover to make close ended. Cover optional. Thanks for this idea!

4. "Normal" fuse holder (like rest of other amps use, not inside)

5. Holes for pots are made .375 (3/8) instead of .3125 (5/16) to allow for bigger pots such as from CTS, etc to fit. Concerns?

6. Holes for "terminal strips" near PT. Caters to the longer strip (7 tabs with 2 grounds at the ends). Let me know if not suitable.

Was thinking of other features like extra tube hole, etc, but this should suffice. I am running so late in this...


Thanks!

Nik

I built my Super Reverb with Alu but switched to steel since then. Even 1mm is strong enough.
Nico

Nic,

I´m a bit late, but that´s what I think about it:

Aluminum (1.5 mm) is what Marshall used ´til they changed over to steel in 1966/67.
The early head chassis were bent from one piece w/ closed ends. They replaced the bent closed ends with aluminum blocks, most probably because they had too many complaints because of the weak material that must carry the whole weight on its bent down ends. The new construction was pretty expensive and still not sufficiently sturdy to support the heavy trannys of their 50 and 100 watt heads.

The 18 watt combo amps had open end aluminum chassis that were mounted with their top side on cab supports. Thus, there was no problem with the relatively light weight trannys.

Steel isn´t just cheaper but much more sturdy than aluminum. 1.0 mm would be way enough, IMO. Plain steel would obviously get pretty quickly rusty. Tin plating would be great, but most amp builders just use yellow anodizing.

Nevertheless, I would use open end aluminum chassis for 18 watt combos due to originality. A head chassis should always have closed ends, no matter if you use aluminum with aluminum end blocks or just steel.

Adrian