Chassis material and tone...anyone TRULY know?

[M Fowler]

Eddie and the Currents was a great band Jana!

[Jana]

No doubt, Mark. But did they use a non-conductive spacer between the chassis and the transformer laminations? All the really good bands did!

[Zippy]

It's all about the Eddy currents (not the Eddie currents )

Are you talking about interaction between PT and OP or something else?

This isn't Twitter, feel free to use more than 124 characters.

[Jana]

I read this one time on the interwebs--take it with a grain of salt. It does, however, make sense from a physics standpoint but whether it matters in a guitar amp I don't know. Anyway, here is the jist of it:

Transformers have eddy currents. When a transformer is close to another conductive material--meaning it is bolted to a chassis--then the eddy currents "flow" from the transformer and into the chassis. The pattern or whatever you want to call it is modified. By using a piece of non-conductive material such as a piece of fiberglass, wood, what-have-you between the transformer and the chassis this "flow" phenomenon is substantially minimized. The thickness of the spacer only needs to be about 1/8 inch. The "coupling" between the transformer and the chassis is interrupted by the space, not the material that was used to make the spacer.

It's on the web someplace, some old time amp designer wrote it. Sorry I can't be more specific.

As we all know, if it is on the web it has to be true!

[Andy Le Blanc]

The other issue is basic conductivity of the metal, that why you see specialty winding's, plating's, etc...

It adds up, grounding, layout, wire type, solder type, transformer gaping, chassis interaction...

If you want to you could make your own 99.999 silver hook up with a 100% cotton insulator.

Its more a matter of selling the "special feature", if the client believes its better
then he'll by it just because it has to be better that way.

The more you debate the issue the more likely someone with pick up on it as a sales point.

EM coupling through the chassis seems a valid argument.
Simply having the PT or OPT on a non-conductive sub chassis, or stand off could address the point in the discourse to a sale.

[Structo]

There do appear to be some valid differences.
Mostly due to the ferrous nature of steel I'm sure.

I believe we have discussed this before so a thorough search may reveal
that thread.

I saw a solid copper chassis before. Not sure about that one.
What about the copper oxide that forms? A green chassis?

As far as what the sonic difference is between steel and aluminum, dunno.

I know the Marshall gang like their steel boxes.

[M Fowler]

Dr Z Tone Quest report:

Mike Zaite noted: I’ve always built my amps on a chromate-converted aluminum chassis.

Why?

In medical electronics, the FDA is very concerned about ground leakage. You can’t scan someone who might be hooked up to life support equipment and risk shocking them, so ground current has to be very, very low. One way we got around that is by using chromate-converted aluminum. Aluminum is already a very good conductor, but the chromate conversion raises conductivity almost to the level of copper without the cost of a copper chassis. The higher conductivity allows for better grounding, better earthing, and when I did this with my amps they were clearly very lively and bouncy with that chassis.

Mark

[billyz]

I know the Marshall gang like their steel boxes.

FYI, Early Marshalls ( JTM 45 )were Aluminum and many old timers believe it contributed to the tonal qualities. Unfortunately, the aluminum Marshall used was light gauge and tended to crack so they switched to Steel.

[daydreamer]

isn't the earth/ground the source of the electrons for the circuit? so the main difference would be if it is part of the electron path/circuit or not. 'the new guy' JDJ, has interesting things to say regarding his wooden chassis on the introduction thread.

Love the idea of copper patena, how old school would that look?! Put that together with a masonite circuit board and it would be a 'steam punk' masterpiece!

Andy

[M Fowler]

You can find copper chassis used in old organ amps for sale on ebay to try out.