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In Reply to: RE: Nothing new under the sun posted by Lew on March 26, 2014 at 21:04:38
Lew, I too saw the 'ground' symbol on Jensen's picture.
If I understand the picture correctly, the 'Load' is the binding posts for the speaker. This means the -ve speaker lead is also going to ground. HMMMMMMM?
Am I safe in assuming the two Bridge's in the MA-1 get paralleled together?, and then connected to the first 4-pole cap?
Follow Ups:
-they are in different power supplies, as two are needed to make the output section run.
What do you think of those Jensen 4-pole capacitors? Not that I would ever think of using them, but Cousin Billy is tempted.
They seem like a nice part.
They will have more effect in a single ended circuit. I'm sure they will affect a differential circuit too, but not nearly to the same degree. Mounting them might be a problem...
from the circuit posted above by Cousin Billy, the ground leg simply runs through the can. There has to be continuity between the negative node of the bridge rectifier and ground at the other end of the circuit he posted. So, what is the benefit of having ground run through the can? Thx.
The same is true of the positive connection.
First, I would not use the word 'ground'! Better to use 'negative'.
The idea is that the cap can be connected in such a way that the internal inductance is minimized. Having the 4 connections brought out allows you to connect the cap in ways that might have some effect on power supply performance- for example one lead at the rectifier, the other connected to the corresponding lead on the filter cap (if being used for bypass).
I found a pdf file on the 4-pole at the Jensen website. It is full of claims without much substance, but it does show a diagram that purports to reveal the internal construction, which is indeed twice as complex as that of a conventional 2-pole capacitor, shown in an adjacent diagram. My problem is that looking at the diagram of the 4-pole, I do not see how continuity is maintained, on either the negative (ground, in my parlance) or positive side, but as you say, it must be. Also, the advantage in terms of lowered inductance is only really significant at very very high frequencies, like over 50kHz and up (based on another figure in the text). The text suggests the idea is very useful particularly for switching and/or "digital" power supplies, where I do understand that lots of vhf hash is generated. But for "our" equipment, I don't know. The cost is about 50X that of a comparable top line Nichicon or Panasonic.
This is kind of what I was interested in, I didn't see how this would be super helpful in a tube amp, unless you have a high voltage switching supply.
Yes, I saw that. The idea is to be able to bypass the internal inductance of the part.
The first time I ever saw this was a good 30 years ago when Sprague was selling film caps with 4 leads on them. I didn't know there was an electrolytic application.
I will try to be as clear as possible;
My MA-1's have a pair of LV 27,000uF storage caps per amp. These caps are feed by two 'bridges'. I will assume these are bridge rectifiers.
There is a positive and a negative wire coming from each bridge. This means I will have 4 wires. 2 +ve, and 2 -ve.
If I am to experiment with a pair of 4-pole caps, then I only need 1 +ve wire, and 1 -ve wire.
I see a few possibilities: A) use one bridge, and leave the other one unused (yes I will put electrical tape around the live wires). B) connect the two positive leads together, connect the two negative leads together, leaving me with a single +ve and a single -ve. Connect these to the first 4-pole cap. C) wire the two bridges in series. In my simplistic mind this will give me 300V. On one hand this will work, since I will be using 500V 4-poles, on the other hand ???????????. This is where my education continues.
Even though I am 53, I can still learn.
You cannot ignore or eliminate either one of the two bridge rectifiers. The circlotron output stage requires two discrete power supplies, each with its own bridge rectifier. If you want to use a 4-pole capacitor in the output supplies, you will need two identical 4-pole capacitors, one to install downstream from each of the two rectifiers, hooked up exactly like the existing filter caps. Treat the 4-pole exactly as any other capacitor, apart from its peculiar hook-up requirement. IOW, when you remove the 27000 uF caps, just pop in the 4-poles. Do not mess with the connections between or among the rectifiers. Bad things will happen. If this is not crystal clear, do nothing.
Danger, Will Robinson.
Lew, I am missing something. The two full wave bridge rectifiers at the back of the amps only run the low voltage storage capacitors. One rectifier per cap. One cap handles one phase, while the other cap takes care of the other phase.
If the 4-pole cap handles both phases in one can, than we no longer need two discrete power supplies. The second 4-pole cap simply helps filter the signal.
If my simple understanding is correct, these storage caps simply add 'ommph' to the signal.
If I had a 500 Ohm speaker, there would be no need for any storage caps. The circlotron would work just fine without.
af
As Lew says, the "4-pole capacitor" does not in any way allow you to use a single supply for the output stage of a circlotron. The two supplies must be kept completely separate, and the 4-pole capacitor would not achieve this.If you look at the pdf on the Jensen site, you can see that the two terminals marked Input- and Output- are essentially connected together, and likewise the two terminals marked Input+ and Output+ are essentially connected together. I say "essentially," because what is actually done is that Input- connects to the - plate of the capacitor foil itself, and Output- separately connects to the - plate of the foil. So there is a tiny amount of inductance and resistance in each of the wires from the capacitor Input- and Output- terminals to the foil, and that is the only sense in which Input- and Output- are not literally the same. Same for the + terminals. If there is any benefit at all from such a set-up, it is likely to be really tiny.
Regarding the quesion of whether the circlotron would work fine into a 500 ohm load without any storage capacitors at all, I think the answer is clearly no. With no storage capacitors on the output power supplies, they would then be providing supply voltages that were just full-wave-rectified sinewaves; i.e. the positive half cycle followed by an inverted negative half cycle (so a positive half cycle agaian), and so on. So the supply voltages would be dropping to zero 120 times per second, meaning that the audio output would be modulated with this 120Hz variation. Specifically, there would be short periods during each 1/120 second interval when the amplifier could output no audio signal at all. Whether the speaker impedance were 500 ohms or 8 ohms wouldn't really make any difference, as far as this is concerned.
Chris
Edits: 03/30/14 03/30/14
Thank you Lew and cpotl, this has been quite a journey and a learning experience.
Since it now appears I would need two sets of 4-pole capacitors, and there is not enough room 'under the hood' to accommodate them, its time to listen to music.
Thank you again.
Music always sounds better than smoke followed by an explosion.
If you are old enough to remember the Johnny Carson Show, you may recall the Great Karnak, as played by Johnny. Ed McMahon would read answers to questions, and the Great Karnak would come up with the questions:
Ed to Johnny: "The answer, oh great one, is Siss-boom-bah!"
Johnny to Ed: "What is the sound made when a sheep explodes?"
The 4-pole capacitor should be thought of in this context as no different from any other standard (2-pole) capacitor. It will NOT handle both phases in one can, in other words. And really, the term "phase" is a little misleading. Think of them as separate power supplies, period.
No, the circlotron would work, I guess, with no capacitors, but you would be listening to a lot of hum and noise. (I won't go into the fact that the balanced output stage does cancel a lot of common mode noise.) The filter capacitors aid the rectifiers in converting AC from the wall socket into DC to run the output tubes. What comes off the rectifiers still has a lot of noise in it. The impedance of the speaker being very high (you mention 500 ohms) would only mean that for extended low bass response you would need less total capacitance than for a typical 8-ohm speaker. The "other" role of the capacitance in this OTL amplifier has to do with facilitating energy transfer from output stage to speakers. In a conventional transformer-coupled tube amp, THAT function is handled by the output transformers.
in any single-ended amplifier, as a convention. (You could also connect the positive speaker post to amplifier ground, which simply inverts the phase of the music signal, as long as you do the same in both channels.) But in our balanced output amplifiers, the amplifier outputs are created equal.My point was that the output from the bridge MUST connect to ground somehow somewhere, otherwise the PS won't work at all. And the fact that your schematic shows the negative node of the bridge rectifier, which to create a positive voltage is the node that must connect to ground, going through the negative sides of the two capacitors, suggests to me that the negative poles on the capacitors are internally connected to each other, i.e., the negative side is like straight wire connection. Which I think is why Caucasian Backplate asked you to measure resistance across the negative posts (input to output). It should be near zero. If it's near zero, what is gained by having those extra connections in circuit? Perhaps to reduce noise, but I really don't know.
Bottom line: Don't invest in these 4-pole capacitors, IMO. You might do a search on Tweaker's Asylum to see what those guys say. They are like "Mikey" in the commercial; they will eat anything.
After writing the above, I did some searching on Tweakers myself. Here is one post that hints at a benefit:
"The whole point of the capacitor is that the negatives don't go to the same point in the circuit.
Forget about ground. Think about current flow in the circuit. The current in both directions flows THROUGH the capacitor and thus, according to the theory, additional filtering is achieved and better isolation between the supply and load results.
Is it better? In some cases I have noticed an improvement, while in other cases it didn't seem to make much difference. I guess, as with most components, it depends on the circuit."
True, the current flows "through" the capacitor, but why this would improve filtering and isolation, I do not fathom, because of what I wrote above; there has to be continuity between the negative node of the bridge rectifier and ground. I would love to do what Caucasian Backplate suggests, to check my hypothesis.
As to your question about "two bridges in the MA1", I would say no, you are not safe to assume they are in parallel. But I know nothing about your MA1; I've never owned an MA1. My guess is that there is only one bridge for the HV supply, as in my amplifiers. The LV supplies for the output stage do require two separate bridge rectifiers, but those are not in parallel either. Here's where I say "ask Ralph".
Edits: 03/27/14 03/27/14
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