OTL Asylum

Posted by cpotl (A) on April 04, 2014 at 10:09:22

In Reply to: RE: Even worse, $400.00 each posted by Cousin Billy on April 03, 2014 at 04:48:48

"This is how I interpret the picture;

A 4-pole capacitor is NOT 2 capacitors in one can. There are however 2 foils in one can.

Think of it this way;
The DC from the full wave bridge rectifier charges the capacitor. This charge is stored in the electrolyte. There is no physical contact between this first 'charging' foil, and the 2nd foil. Except of course by way of the electrolyte. If the full wave bridge rectifier has any type of noise on it, or coming from it, the 2nd foil does not see it, or see's much less of it. I would think this allows the capacitor more 'smoothing' ability for the DC ripple.

The second foil now has the input coming from the 6AS7's (+ve screw), and outputting to the speaker binding posts via the (-ve screw).

Here is the only problem I forsee;
As Lew has stated, the FWBR needs to somehow be grounded somewhere. The Mundorf 4 poles are NOT grounded together internally. HMMMMMM.

We know the A-S MA-1's use a floating ground. This will not pose a problem on the 4-poles output, because the 6AS7's are grounded at the tube bases (anode?/cathode?)."

A capacitor always has two foils in one can (leaving aside the entirely separate discussion of cans containing two capacitors, since it is not relevant here). In the Mundorf 4-pole electrolytic, there are two foils just like in any other single capacitor. One is the positive foil, the other is the negative foil. They shoose to make two separate connections to the positive foil, and run them out to two separate + terminals. They also make two separate connections to the negative foil, and run them out to two separate - terminals. To a first approximation, the two + terminals are identical, and might almost as well be viewed as being the smae connection. There is a continuous metalic conducting connection between the two + terminals. Likewise for the two - terminals.

Possibily, there are minor benefits to keeping the "charging circuit" from the rectifiers distinct from the "output circuit" going to the amplifier. But it hardly seems to be worth the trouble, and expense, to do that.

The issue of grounding is a bit of a red herring here, I think. Mundorff happens to display an application schematic which, like most common-or-garden applications, has one side of the capacitor (the - side) grounded. The circlotron is a rather atypical application where neither side of the power supply(s) is connected to ground. So one should not be hung up on the fact that Mundorff happens to show an application where one side is grounded. In the circlotron, neither side should be grounded (and so none of the four terminals on the 4-pole capacitor should be grounded).

Chris