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In Reply to: RE: Anyone try a 4-pole capacitor? posted by Cousin Billy on March 26, 2014 at 10:55:09
The hook up recommended is supposed to lower the impedance of the two caps and also lower noise. Jensen did not invent this apparently companies like Sprague manufactured those four pole caps. I have a bunch but never tried them as it struck me as being very odd and suspect (100 uF at 450 V x 2) in a relatively small container measuring roughly a cube 2 inches on a side
Follow Ups:
Hello unclestu
I am learning a lot with this thread.
The Mundorf website gives a better description. Go to HiFi/Studio on their website, click on Power Capacitors, click on (application). There is a great picture.
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?).
IF the FWBR needs to be grounded in order to supply DC to the storage cap, than I will need advice from you fine folks as to 'where' to connect it, and how.
The biggest problem of all?
A 200V (or 250V in Mundorf's HP+ case) 22,000uF storage cap is not a common size. This would be a special order type scenario. There is a minimum order of 18pcs, and they are around $400.00 each. OPPPPPPS.
"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
I chose the Mundorf diagram only to point out the fact that there cannot be two unconnected foils in the capacitor, because in that case the bridge rectifier would not see ground, in their diagram.
In the circlotron, at least in the Atma-sphere version, the negative side of each of the two supplies is floated from audio ground by a 600R resistor. The voltage dropped across those Rs at idle is (I actually forget the exact value) certainly under 2V, more like 1V. So the supplies are indeed not grounded, but hovering close to it. Kind of like a tethered dirigible.
If the amp develops a DC offset, one speaker post will be negative and the other will go positive WRT ground.
What I said was that the two negative poles MUST be in continuity, because only that way do you get a connection to ground through one of these 4-pole capacitors, as shown in their own diagram. That hook-up they show would not work to produce a positive DC voltage unless the negative node of the bridge rectifier is in direct continuity with ground. Then someone else smarter than me pointed out that the positive poles also must be in continuity, even though the cartoon diagram suggests two separate functioning units in one can. I don't blame Uncle Stu for his confusion; the ambiguous blurb on the Jensen website does not help. But you are correct to say the 4-pole capacitor is ONE capacitor with a novel input/output strategy said (by Jensen) to reduce inductance, which only comes into play at extremely high frequencies.
-Are always expensive. That's actually a great price especially given the small quantity.
FWIW if there is noise in the rectifier it will indeed be seen by both sides of the cap.
What the 4-lead parts do is bypass the internal inductance of the cap. In this way you could tie the 2 positive connections together as one, and the same for the minus side and get the benefit of the part. That of course makes one wonder why the part could not simply be made that way and just bring the resulting connection out as two terminals rather than four.
But there is another way to do this. The amp is wired in such a way as to minimize the effects of the internal wiring in the output stage- that is why there are some rather large bundles on the speaker terminals. But the speaker terminals are connected to the minus of the filter caps.
So what you could do is bypass the wiring by installing an additional pair of caps which have the negative side connected directly to the speaker terminal, then what to do with the positive side... you could connect those back to the correct connections on the filter caps...
We've done this before of course. Not a lot of effect FWIW. I don't see how the 4-lead part would help you as it does not allow you to bypass the wiring in the amp as I just described. In thinking about it I don't see the benefit of the extra leads. If you treated them as an extra terminal the current on say the positive lead would have to move through the foil, which may or may not be a good thing. If it were me doing something like that I would make two wiring harnesses to deal with the two sets of leads.
You can see that there is a diminishing return here...
Ralph, You're talking about adding capacitance right AT the speaker terminals, correct? If so, I have thought about that many times, but the problem, as you suggest, is how to connect the other end of the capacitor. It would be most convenient to connect it to the nearest positive pole, which is the pole coming from the PS on the opposite side of the circlotron. This is why I have not tried it, but is there really anything wrong with connecting to the pos of the bridged supply? I thought about using a film bypass cap right at the speaker terminals, in which case there is no polarity to worry about.
On the other hand, the internal wiring going up to the speaker terminals is very high quality and can be thought of as just another foot of speaker wire, I guess.
If you look at how the wiring is set up, you will see that while we are using something that looks like speaker cable, its not actually carrying the finished signal. Instead, that is assembled on the speaker terminals themselves, that is why the bundles from the power tubes are connected at the speaker terminals rather than at the power supplies. So the 10ga wire is simply the current return back to the power supply. The bundles going to the individual tubes are all cut to the same length. That's why the internal layout has the look that it does.
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