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In Reply to: RE: Jensen website posted by Lew on March 28, 2014 at 07:11:10
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.
Follow Ups:
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.
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