Shields for 6C45pi Tubes

[adydula]

Wondering why these tube need shields?

Gain? Susceptibility to RFI? etc...

Also I am wondering why in the Mainline the "drain" is cut off on one end of a shielded cable? and why not ground both ends??
Ground loops??

Alex

[Paul Birkeland]

Wondering why these tube need shields?

The shields will reduce the sensitivity of the tubes to whatever environmental noise there may be.

why not ground both ends??

That would make a loop and ultimately grounding both ends doesn't offer any benefits.

[adydula]

Thanks Paul...

So why dont we use them on the 12AU7?
My guess is because its not a signal tube in this use?


Also was wondering about AC vs DC heaters?

Alex

[Paul Birkeland]

The 12AU7 is in the power supply so noise pickup isn't such an issue.

We use DC on the heaters because it's a bit quieter than AC.

[adydula]

Paul,

Again thanks for taking the time to answer my questions.

When you look at the schematic for Mainline its really straightforward, uncomplicated design.

Simple when done "right" is good, where voltages are clean and well regulated for varying loads etc over a range of opearting conditions.

It looks like you guys picked a great tube and a really thought out the design very well.

Alex

[AllanMarcus]

When you look at the schematic for Mainline its really straightforward, uncomplicated design.

Simple when done "right" is good, where voltages are clean and well regulated for varying loads etc over a range of opearting conditions.

It looks like you guys picked a great tube and a really thought out the design very well.

“Any fool can make something complicated. It takes a genius to make it simple.”
― Woody Guthrie

or

Any damn fool can make something complex; it takes a genius to make something simple.
-- Pete Seeger

Both quotes apply :-)

[Doc B.]

"It can scarcely be denied that the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience."

Albert Einstein,"On the Method of Theoretical Physics" The Herbert Spencer Lecture

This has often been paraphrased as

Everything should be made as simple as possible, but no simpler.

[AllanMarcus]

Doc, you made something simple complicated!

[Doc B.]

I made it as simple as possible and no simpler. So many great quotes lose resolution in an effort to make them fit a common denominator.

That's rather like the Mainline for me. I find that the notion that seems to be considered simple - the single gain stage - in reality calls for a rather complex and tricky design to pull it off. I had a bit of a time talking the guys into working on it initially.