Electroloy

[Andy Le Blanc]

In all of the debate of chassis styles, aluminum, steel etc..... one topic that
seems to have been missed is just exactly what these old amps and other
devices were constructed upon.

I found an old reference of "electroloy" or "radio metal".
Its what all the old consumer products were made on.

Are there any current manufactures where the material can be sourced?

Or are we all stuck having to make do?

[M Fowler]

Here is a tone quest interview with Dr Z and he discusses chassis material.

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.

The early Marshall amp chassis were aluminum…

They sure were, and so were the Trainwrecks. Aluminum is a lot more expensive than steel.

[ToneMerc]

I found an old reference of "electroloy" or "radio metal".
Its what all the old consumer products were made on.

Are there any current manufactures where the material can be sourced?

I believe electroloy was industry name for a copper and cadmium alloy.

TM

[Andy Le Blanc]

I've been digging, it's an old trade name, a manufacturing group in asia holds
it now, maybe a small company in N. American. Theres several firms that
do plating and custom plating but mostly galvy. There's a firm that does
mil. spec. relay contacts etc.....

Its a very simple thing. I got past much of this by not using the
chassis as a ground where ever possible, it becomes a decorative shield.
Get past all the wasted investment in materials with proper grounding.
With simpler amps its easy, the more elaborate the design the more forethought.
Why waste time with aluminum, the only reason to ground though the chassis
is lazy convenience.
Now the only concern is corrosion inhibition, not reinventing the wheel here.
No need to run up the cost with exotic material either.

[Phil_S]

Why waste time with aluminum, the only reason to ground though the chassis is lazy convenience.

Andy: Please explain. I just don't follow. Are you saying to float the ground?

[Andy Le Blanc]

You've hit the nail on the head, but not how you might think.
Ground and chassis ground are not equal, the chassis is what is creating the
floating ground. That's why different materials are believed to improve the
performance of the amp. Using the chassis as a ground plain denies you
any control over the ground, its a big resistor. It creates all kinds of
coupling issues from the very beginning of the signal chain.
Even the symbology is different. Most old tube amps were designed around
the old two wire 110ac system, they had to create a floating ground off the
power supply. No sense clinging to that, the quality of your ground is what counts.
And you don't have to fork over the dough for it either.

[M Fowler]

Your still attaching to the chassis in your picture but by not having random grounds all over the place you only need the PS ground and then the rest of the amp gets its own ground source.

[Andy Le Blanc]

Differentiate the ground plains. Its very basic, and the foundation of "star" grounding.
This also separates old designs from anything new that incorporates a pcb.
The ground plains are separate by design. You can use a copper bus, or wire.
As long as you respect the difference between ground and chassis.
Why use aluminum? The new plastic input jacks are enabling.
Even when using the old standoff's, if you are careful to at least get the input
ground off the chassis, you have a better amp. Carry the concept thru the entire
amp you have the control, and can choose the conductivity of the ground
with a single wire, without investing in costly materials. The chassis looses it
importance except as a shield and parts container.

[M Fowler]

Or just keep the low level signal grounds, medium level signals and high level signal/PS to their three respective ground lugs.

[Andy Le Blanc]

Its more practical to give the first couple PS filter stages their own return to ground.
Get the input off the chassis, use a new fangled jack, I don't like plastic jacks,
but you dictate the ground.
lets say you've got the PS cared after, the chassis will shield the pot's, so don't
create a loop by grounding to the pot. body. It's tempting. Outputs like verb
are ok to use the chassis ground, simple as jack choice.
Use a UL certified product for the lug, with the appropriate ground bolt,
you know, the green coated things, you can even torque the bolts of the lug
to the recommended psf if your inclined.
Once you have the ground runs isolated, use a wire type of choice for the
long runs back to your ground lug, say copper or nickel, silver.
This is a spot in the lay out where you can audition wire types.
You have control and the chassis isn't allowed to cause issues.

[M Fowler]

Andy I sure do agree with you about not soldering to the pots or using them as the ground reference ala TW style. I see it done with many different builders including Dr Z.

But I have decided when not building TWs I would avoid that practise.

Those green grounding bolts your talking about is that the bare wire ground in recepticles and breaker panels your talking about? I don't go that large. I seldom use the Tranny bolt either. I just prefer to drill my own main filter cap grounding lug location avoidng the tranny bolt.