PT and OT transformer core orientation

[Helmholtz]

I also vote for using headphones to orient transformers

Yeah, that's what I did 40 years ago. I used a cheap "crystal" piezo earphone connected across the OT primary. Worked great. Meanwhile I have a scope.

[jmaf]

Check out pages 5-13 of this preview

https://books.google.com/books?id=Mw...page&q&f=false

Can't praise Morgan Jones' books enough.

The other volume, about tube amp theory, is probably one of the best tube amp texts you can buy.

Because of this particular book I started building my own mixed aluminum + brass chassis.

I needed good electrical conductivity for my star grounding with as little as possible magnetic conductivity.

This is what I came up with:



The mid section is 2 to 3mm thick brass or mixed aluminum with a thin sheet of brass under it (note on side photo below). (Pure 3mm brass is too expensive so for my experiments I used aluminum + brass.) I could then easily solder electrical terminals to the brass layer that faced the circuit.

The structure was made out of L shaped aluminum profiles (aluminum chassis assembly idea copied straight out of Morgan Jones book) as such:



My transformers would sit on the brass or aluminum middle section.



Zero magnetic noise. (And electrical conductivity for proper grounding don't get much better than brass.)

Out of respect for square law m-field, I always set the transformer laminations at 90 degrees regardless of how far:

[Helmholtz]

And electrical conductivity for proper grounding don't get much better than brass.

Copper and aluminum are better electrical conductors than brass.

[jmaf]

Copper and aluminum are better electrical conductors than brass.

Most amplifier chassis are made out of steel. My experiment was an attempt to improve on that.

The above amplifier is dead quiet which is what I wanted to achieve.

[catalin gramada]

Copper and aluminum are better electrical conductors than brass.

Sometimes I used this kind of brass pipe (3 mm dia.) for long grounding bus (meant double surface conduction for same section). I did not notice any diferences in term of noise in respect with cooper bus wire. One remark think should be done regards physical contacts between cooper/brass and aluminium as both tends to protect by auto oxidation and in contact each with another develop thin layer of oxide which maximise residual resistance.

[jmaf]

Sometimes I used this kind of brass pipe (3 mm dia.) for long grounding bus (meant double surface for same section). I did not notice any diferences in term of noise in respect with cooper bus wire. One remark think should be done regards physical contacts between cooper/brass and aluminium as both tends to protect by auto oxidation and in contact each with another develop thin layer of oxide which maximise residual resistance.

[ATTACH=CONFIG]54885[/ATTACH]

You shouldn't have to solder brass/copper and aluminum.

The main point here is that the transformer will always induce some tiny current on a steel chassis but not on aluminum or brass.

The tiny electrical conductivity differences between metals in chassis-distances won't generate perceivable voltages with signal-level currents. The metal conductivity was picked from my reply but it was definitely not the main point. Brass is acceptable, that's the point.

[Helmholtz]

I did not notice any diferences in term of noise in respect with cooper bus wire. One remark think should be done regards physical contacts between cooper/brass and aluminium as both tends to protect by auto oxidation and in contact each with another develop thin layer of oxide which maximise residual resistance.

For electrical resistance only cross section and specific conductivity matter - not surface. Low electrical resistance only matters with high ground currents. In most cases a heavy gauge copper bus is the best solution.

Only aluminum is known for noteworthy auto-oxidation, that's why it isn't easy to solder.

Especially if you have a ground loop also ground path inductivity matters.