| dantwomey |
LC Audio describes "the theory" behind their capacitor connections in their Class A amplifier and they describe something they call "current woppling". Would this be an issue for one of our DIY projects where we connect a number of smaller capacitors in parallel to create the necessary PS capacitance? To explain it in further detail. If my Aleph-X requires four 22,000uf caps in its PS I was under the impression that I could parallel up four 5600uF caps to form each 22,000uF cap. Am I off track here?
| quote: | | Our novelty Virtual 4 pole Capacitor bank is one example. In this bank 10 high speed low impedance power electrolytic capacitors are connected together to form 2 big caps for the amplifier rails. None of these caps are connected in parallel, as this would pose problems with current transfer woppling. This is when several low impedance caps are connected directly in parallel, they tend to compete for the power. The first cap gets current first, then the next tries to take some of the charge from the first, and so on. In terms of sound performance, you get a loss of precision in the high frequencies and a cold midrange at larger power outputs - where the woppling is more severe. One alternative is to use only large can capacitors. This to some extent also will solve the two problems described, however almost any large can capacitor will work very slowly, and play with a slow and out-of-beat bass. The V4P setup however solves both problems! Bass is fast and in sync, while precision in mid and high ranges are intact at all levels. Due to the special V4P network, power is charged and discharged to each cap at exactly the same time and rate. At the output of the V4P network no electrolytic caps are present, so here we found a perfect opportunity to place a huge Polyprop (22uF) which this way will be the only capacitor the amplifier can 'see' above 1 kHz. |
Regards,
Dan |
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| Nelson Pass |
I say that's mostly ****. This has been mentioned before,
and after considerable thought, I realized that interactions
(if any) between unmatched parallel caps is of no consequence. |
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| neutron7 |
| Do they mean "current wobbling" ? I have heard of that but not "woppling" which if it is a real word, is so obscure that google only has 1 hit :) |
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| Richard C |
| If 'woppling' isn't a real word, it should be :) |
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| roddyama |
| If the word "woppling" exist, I would say that LC is getting one here.:smash: |
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| grataku |
| quote: | Originally posted by Nelson Pass
I say that's mostly **** |
yep, sounds like a real WALLOP of it.
On a related note, why do I find that my amps stay on for longer after I power them off if I have a couple of nice big blue computer grade caps instead of the same amount of capacity split into dozens of Panasonic FC or other similar caps? |
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| Christer |
Can I have a double Wopple cheese and a can of Black Gate,
please? :xeye: |
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| Fred Dieckmann |
One entry found for whopper.
Main Entry: whop·per
Pronunciation: 'hwä-p&r, 'wä-
Function: noun
Etymology: 1whop
Date: circa 1785
1 : something unusually large or otherwise extreme of its kind
2 : an extravagant or monstrous lie
Maybe it is the verb for telling a whooper...... |
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| Lars Clausen |
| quote: | | I say that's mostly ****. |
I'm sorry Nelson, we didn't invent this phenomena, it was explained at a passive seminar by the norther European representative of Chemicon (Former Sprague) Capacitors factory.
Now it was back in 1991, so i'm sure the word woppling is not the right word he said, but the phenomena is real enough.
If you have say 5 capacitors in parallel, in a dual rail connection, where the rectifier is in one end, and the amplifier is in the other, and we decide the ESR of each capacitor is 10 milliOhms, and the connection resistance between each capacitor is 2 milliOhms.
Do you (Nelson Pass) dispute that the capacitor nearest to the rectifier is charged with the largest current (since it has only 10 mOhm ESR) , and the one furthest away is charged with only about half the current (since it has 20 mOhm as seen from the rectifier). Then when the charging spike is over, the charge rolls forward from the first capacitor to the last and attempts to equalize the charge over the entire bank. So each capacitor ends up having the same voltage. This is what i have (maybe wrong word) called current woppling. |
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| Lars Clausen |
Just wanted to add the schematic to our solution discussed. So easier to follow.
Sorry the text is in Dansih language, but the schematic should speak for itself.
The resistors ensure that the charging spike is equally distributed over the entire capacitor bank, and also equally discharged from all 4 capacitors to the amplifier.
I will just emphasize one point, so everyone in here can understand, also Fred: :D Only the positive side of the power supply is shown here on this schematic. There need also be a corresponding negative side of this power supply circuit to make it work properly. |
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| Lars Clausen |
Just an additional point: I also find it to be sound degrading to connect any capacitors of any kind in parallel with Black Gate's, they simply work better on their own.
Further parallelling transistors / MOSFET's especially in output stages will always result in loss of resolution in the mid-high region, and add harshness to voices. This is because their VBE / VGS curves do not match exactly. As the current changes, high order distorsion is added to the signal. And no you can not use a feedback loop to remove THD in the amplifier chain, however you can by using feedback with a non linear element in the loop create a modulator. This basicly means you convert THD into TIM.
Better avoid THD alltogether. |
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| Nelson Pass |
If you re-read my comment, you'll see that I have made an
allowance for the actual existence of such a thing. I merely
dismiss it as not a real problem. |
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| Lars Clausen |
Nelson: Then consider this setup of the two capacitors in parallel, when you view it as the capacitor's practical equivalent circuit.
As you know every capacitor consist of a capacitive part (obviously), an inductive part and a resistive part (last two from wire leads and internal windings of the aluminum foil). There is also a fourth part a parallel resistor, but it has no significance in this discussion.
When you have one capacitor it will act as a series filter with it's lowest impedance at one specific frequency. But when you parallel two caps, they can interact with each other's internal circuit. Especially if the inductance or capacitance is not exactly matched. (Which they can never be in a real-life scenario).
Consider the possibility that C1 might form a parallel resonance with L2 and vise versa. Might occur if the parallel connection resistors (here 1 milliOhm) are low enough. I think that anyone can see that would be a problem in your amplifier power supply.
In the V4P circuit shown above, the problem is eliminated by breaking the circuits apart into separate series filters. |
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| Fred Dieckmann |
'I will just emphasize one point, so everyone in here can understand, also Fred"
I wonder how much the benifits of this are from lowering the Q of each of the caps that are in parallel and the reduction of charging current by the additiona series resistance. Lowering the Q of caps in parallel when adding bypass caps is probably a good idea to avoid resonant circuits from the parasitic inductances interacting with the capacitance. For an extremely low ESR cap like the Black gates or Oscons bypassing is not a good idea unless you really understand the capacitor and PCB parasistics. It seems that current sharing effect could be largely acheived by making sure the PCB ESR of traces between cap terminals is less than that for the traces to rectifier and from the caps to the load. Also each of these traces should have have the same resistance to distribute the currents equally. As for telling whoppers.......
Truth is the most valuable thing we have. Let us economize it.
Familiarity breeds contempt. How accurate that is. The reason we hold truth in such respect is because we have so little opportunity to get familiar with it.
Mark Twain |
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| Christer |
What about the following solution? The upper one is frequently
recommended as "the proper" way to connect PSU caps in
series to even out the lead impedances. The schematics are
intended to reflect the physical PCB layout.
Now, what about extrapolating from this to the lower figure,
where I intend the bridge connected between a and b and
the load between c and d. I don't think it will even out
differences between the caps (too late to think properly now)
but at least it evens out the lead impedances and you get
rid of the extra resistors. These may be beneficial on the bridge
side, but hardly on the load side, or...? |
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| Petter |
I agree with Lars that two units with resonant frequencies that are different could cause beats - this is common to many situations in engineering sin(a) + sin (b) = Look it up.
Whether that is a problem or not in this case I don't know. We should try it and evaluate.
Petter |
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| Christer |
| quote: | Originally posted by Petter
I agree with Lars that two units with resonant frequencies that are different could cause beats - this is common to many situations in engineering sin(a) + sin (b) = Look it up.
Whether that is a problem or not in this case I don't know. We should try it and evaluate.
Petter |
But do you really gain anything from parallel caps instead of
a single bigger one i this case since the resistors add to the ESR? |
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| angel |
If I understand this effect correctly, we're dealing with ever so slight differences in the rise time of the supply capacitors, due to their different capacities, and the different resistances between each capacitor, and whatever charges it. Please correct me if I am wrong.
While paralelling several RCR sections should improve current sharing, at least during most of the charge cycle, it does not entirely eliminate this wobbling, as the (typically) +/- 10% tolerance of the capacitors will cause a difference in rise time that I expect will swamp the resistance. If aiming to eliminate this effect, we would also need to match the capacitance of our cans.
Apart from that, I think the PSU schematic presented by Lars makes for a sensible positive half.
Anyway, such 'charge sloshing' between capacitors will be well covered during the course of this debate, I expect, so I will bring up another point that I, for one, am curious about.
Constructors of CLC supplies and such will be familiar with the idea of placing the smaller cap earlier in the chain to avoid oscillation during changes to the load.
Since most of us tend to invest a tremendous amount of effort in keeping high frequency garbage from our circuits, should we not also examine the potential for high frequency oscillation due to interactions between the load and what essentially is a CLC supply with low values for L?
Lastly, I would point out that I have done a brief experiment on parallelling capacitors for a headphone amp at some earlier time, and there was a slight subjective improvement in reverting to a single cap. I believe I might have been the one who mailed Nelson about this at that time, slightly prior to doing the experiment.
PS! Lars: 330uF polypropylene caps are readily available in Scandinavia. How about trying a similar PSU technique for the Sidewinder, but with PP caps in the RCR bits? ;) |
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| Cybergent |
I think, when discussing load distrubution and differential currents between different caps, you also might talk about the same effects inside a single large cap as nobody can guarantee, that the electrons are equally distributed on the internal surfaces as well.
You can view a large cap as a combination of many little ones.
But all this is a more theoretically aspect than a practical, as I personally think the effect is cancelled out the more caps you use. Proper connection of those estimated.
I do not think, that desperately making the overall features worse by adding extra resistance to avoid those effects will result in any final benefits. |
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| mrfeedback |
| "The Original WHOPPPER® Sandwich has been doing its thing since 1957. It's a fire-grilled classic and everything you would expect from a great-tasting burger – 1/4 pound of beef, red ripe tomatoes, crisp lettuce, creamy mayonnaise, ketchup, crunchy pickles and onions all on a freshly baked bun. Add extra ketchup and HAVE IT YOUR WAY®." |
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| cowanrg |
now THAT'S something that makes sense!
| quote: | Originally posted by mrfeedback
"The Original WHOPPPER® Sandwich has been doing its thing since 1957. It's a fire-grilled classic and everything you would expect from a great-tasting burger – 1/4 pound of beef, red ripe tomatoes, crisp lettuce, creamy mayonnaise, ketchup, crunchy pickles and onions all on a freshly baked bun. Add extra ketchup and HAVE IT YOUR WAY®." |
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| mrfeedback |
The biggest lie (whopper) is suggesting that eating those things is good for you !!!. :bigeyes:
Eric. |
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| grataku |
| Seems to me that the problem could be solved to first order by NOT having the rectifier on one side and the output on the other. I don't get what the C(RCR)nC arrangment is doing. |
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| mrfeedback |
Ime, taming psu resonances is always a sonically good thing.
Eric. |
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| cowanrg |
| i know im an idiot with electronics, but wouldnt it make sense to just use two caps? or, (thinking outside of the box, and i shouldnt even be allowed near the box), what if you had multiple rectifiers with pairs of caps after? |
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| ScottRHinson |
| quote: | Originally posted by Lars Clausen
Just wanted to add the schematic to our solution discussed. So easier to follow.
Sorry the text is in Dansih language, but the schematic should speak for itself.
The resistors ensure that the charging spike is equally distributed over the entire capacitor bank, and also equally discharged from all 4 capacitors to the amplifier.
I will just emphasize one point, so everyone in here can understand, also Fred: :D Only the positive side of the power supply is shown here on this schematic. There need also be a corresponding negative side of this power supply circuit to make it work properly. |
Wouldn't this circuit just increase the ESR of each cap? Then to account for the increased ESR you have to put a high quality bypass cap on the whole network?
Scott |
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| angel |
As to the bit about raising the ESR, well, not really, but it raises the net resistance of the power supply, although by an insignificant amount, further mitigated by the small, high quality cap on the output.
More relevant, it raises the resistance seen by HF noise, which might otherwise just 'bounce' past the caps, never even seeing a path to ground, due to the slowness of the caps. Now the HF will at least 'see' a small series resistance, then a fast cap, forming a good low pass filter.
Also, raising the resistance, without affecting the reactance, yields a lower Q factor, which means you are damping power supply resonances.
The slightly raised rise-time also serves to protect the rectifier, as well as reducing noise spewed back onto the mains.
For class A/B amplifiers, where the average power may be significantly lower than the peak power, you might want to use such a supply, and use higher value input resistors (less load on the presumably small transformer, which is sized based on average load), while retaining the low value output resistors, for better transient response.
As to just using two caps, that makes sense, if they are fast enough. Unfortunately, the larger a cap is, the slower it tends to be.
Of course, there are many solutions to this problem. I'll just list a few.
(A) Go with what Lars did, and build a power supply with controlled resonances and better load sharing, using many small, fast caps.
(B) Use a polypropylene cap instead. Unfortunately, they come in small capacities (I've seen none bigger than 330uF), so you would have to use high voltages to exploit their storage capacity, and a switcher to step the voltage down.
(C) Use stages that consume a constant amount of current, such as differential stages (e.g. the Son of Zen or BZLS). These should be indifferent to the high frequency capabilities of the power supply. In fact, slow caps might help the CMRR at high frequencies, as any imbalance tends to be degenerated by the low compliance of the supply.
(D) Use full or partial shunt regulation of your supply, so that your HF response is dependent on the shunt circuitry, rather than the slow caps. For example, use a depletion mode FET from the rail to ground, with a resistor on the gate, and a cap from the rail to the resistor.
(E) Do what Lars did, but parallell hundreds of small caps instead.
(F) Do what Lars did, but switch the resistors for inductors instead. Select the values, including the Q of the inductor, carefully. You must be especially careful of the output, as you don't want ringing from interactions between the smaller, fast cap, and the inductor, during load variation.
(G) Any combination of the above.
(H) Forget about it, and just build an "audiophile" grade switch mode power supply, throwing such concerns as 'efficiency', 'low cost', and 'cool operation' out the window.
Just my 2 cents. |
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| cowanrg |
| could someone simply and plainly explain what a switching power supply is?:( ive heard it a million times, and all i know is its supposed to be bad for audio and computers have them. |
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| angel |
The term 'switching power supply' refers to a different kind of power supplies from what you are used to (those are called 'linear supplies')..
There are a lot of audiophile myths about switching supplies being bad, and if you want to dispel them, go have a listen to some of the high end products from e.g. Linn, that use switching supplies. Theirs are so good they even eliminate any gains from filtering or fancy power cables, which is hard to do, regardless of the kind of supply you use.
Basically, a computer grade supply is bad because it is built from overly cheap components, and designed to save money.
As to how switching works, it depends. The most basic thing is, you chop up the alternating current from the mains into pulses, that are deposited into capacitors as usual. The number of pulses per second, or their energy content, or both, can be shaped in a number of ways, allowing good regulation, and ideal mains loading.
Good results can be achieved through hard work and good engineering. Bad results are easily achieved by cutting corners or bad engineering. Regardless of whether you use switched power supplies, or linear power supplies. The skill threshold for using the switching technology successfully just happens to be a bit higher.
It is simple enough to build hybrid supplies, though, where a transformer, rectifier, and cap, provide a high voltage DC supply, and some transistors, resistors, an inductor, a capacitor, a diode, and a voltage reference (e.g. zener), let you step down the high voltage to a lower, more useful voltage.
Of course, any kind of switching process generates noise, and you have to deal with it. Which is a topic that is common to switched and linear supplies, frequently addressed with large inductors, fast capacitors, regulation, and so forth.
Hope this clarifies. |
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| Cybergent |
| quote: | Originally posted by cowanrg
could someone simply and plainly explain what a switching power supply is?:( ive heard it a million times, and all i know is its supposed to be bad for audio and computers have them. |
Look here: http://henry.fbe.fh-darmstadt.de/smps_e/smps_e.asp |
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| angel |
I fail to see how doing everything seperately is going to do significant good, except if they are using seperate transformers, in which case there would be no current sharing issue (the core stores energy, as I recall?). And I read your post as stating that they only use seperate windings.
Their approach fails to lower the Q of any power supply resonance, and might for that matter end up with a higher net resistance from the power supply than what the LC Audio solution achieves.
And Lars only needs one transformer, two bridges, and two decoupling caps, which allows him to put more money into their quality. Also, less mounting work, logistics, etc., means he does not have to spend as much money on things that are not better parts, leaving more money to spend on said better parts. Unless I am mistaken, that decoupling cap is a Mundorf supreme.
Kudos for Spectral being willing to go to such an extreme, though. Now, if they had only spent that effort on something else...
I imagine the mounting costs (labour etc.), and the costs associated with using nonstandard transformers, would easily sum up to what it might cost them to implement a high quality AC shunting supply, and possibly get rid of caps altogether in the process, depending on how constant the load presented to the supply is. |
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| peranders |
| quote: | Originally posted by Lars Clausen
Just wanted to add the schematic to our solution discussed. So easier to follow.
Sorry the text is in Dansih language, but the schematic should speak for itself.
The resistors ensure that the charging spike is equally distributed over the entire capacitor bank, and also equally discharged from all 4 capacitors to the amplifier.
I will just emphasize one point, so everyone in here can understand, also Fred: :D Only the positive side of the power supply is shown here on this schematic. There need also be a corresponding negative side of this power supply circuit to make it work properly. |
At audio frequencies, what effect had this unequal current? |
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| Cobra2 |
As a side-note...I think even Lars have found that 2 better quality caps sounds better than his "VPI-4"(?) psu....???
That is my experience with the ZapPulse...BlackGate/SE or not...
Arne K |
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| Christer |
| quote: | Originally posted by mrfeedback
The biggest lie (whopper) is suggesting that eating those things is good for you !!!. :bigeyes:
Eric. |
At least they admit it. :)
I wonder if they were aware of the double meaning of the
word when coming up with that burger name? BTW, I just
looked it up in my Oxford and instead of just listing the two
different meanings they define whopper as "something
unusally big, especially a big lie". :):) |
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| Lars Clausen |
Cobra 2: You are so right!
Also we only use the V4P solution in our Class A amplifier, and multichannel PWM's where large capacitances are absolutely nessescary.
In 2 ch. amplifiers with PWM modules 2 good caps will do better than V4P any day of the week. Practical tests show that a good PWM amplifier of 2 x 250 Watts RMS essentially require only two
2200 uF / 100 V capacitors (yes 2.200 not 22.000) to reach a good sound quality level. So the solution in that case is as you mention a couple of good caps.
A Class A amp can't get enough capacitance, so here we need to use at least 50 - 100.000uF. But unfortunately i have not seen any good capacitors of say 100000uF 50V....
Peranders: If you were to draw a curve of your power supply's impedance at different frequencies, also in the audio region, i think you would 'bump' into the answer. Pun intended ;o) |
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| Nelson Pass |
| quote: | Originally posted by Lars Clausen
Nelson: Then consider this setup of the two capacitors in parallel, when you view it as the capacitor's practical equivalent circuit.
As you know every capacitor consist of a capacitive part (obviously), an inductive part and a resistive part (last two from wire leads and internal windings of the aluminum foil). There is also a fourth part a parallel resistor, but it has no significance in this discussion.
When you have one capacitor it will act as a series filter with it's lowest impedance at one specific frequency. But when you parallel two caps, they can interact with each other's internal circuit. Especially if the inductance or capacitance is not exactly matched. (Which they can never be in a real-life scenario).
Consider the possibility that C1 might form a parallel resonance with L2 and vise versa. Might occur if the parallel connection resistors (here 1 milliOhm) are low enough. I think that anyone can see that would be a problem in your amplifier power supply.
In the V4P circuit shown above, the problem is eliminated by breaking the circuits apart into separate series filters. |
I can't resist beating on this subject, so I apologize in advance.
Particularly referencing the diagram which was included from the
above (quoted from page 1), the analysis is incomplete. It
neglects the inductance and resistance of the voltage source,
the inductance of the connections between the capacitors,
the effect of the load impedance, the effect of any CLC or CRC
filtering deliberately employed, and the effect of any bypass
caps.
In fact, once you include the inductance between the cap
connections, you can start arguing that you have a C(L+R)C filter,
and in the posting before the one just quoted, maybe 9 poles of
such. I usually go to considerable trouble to make such
supplies. ;)
Certainly high noise current and voltage are going to fly around
in the system after the recifier diode, whether you parallel caps
or not, and I continue to insist that this effect is miniscule by
comparison, and is removed by the same mechanisms that
remove the main ripple effects. |
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| Da5id4Vz |
| Well it did have an RTA on the front panel... |
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| Fred Dieckmann |
I believe that the point the guy explaining this to Lars was trying to make is that if attention is not paid to PCB and wiring impedance, the caps can very well have different ripple currents across them. One of the reasons for using multiple capacitors that each individual capacitor is not rated to carry a disproportionate share of the ripple current and that the ripple current is to be divided equally by the number of caps in parallel. This prolongs the life of the capacitors and is just good engineering. I have a feeling that it was the in the context of wiring and PCB impedances that this was presented.
The addition of resistors between transformer and rectifiers is not a bad idea either. It limits the peak current through the transformer reducing saturation and current through the rectifiers which effects reverse recovery time and RFI. the parallel equivalent of four 0.1 ohm resistors is 25 milliohms which is in the range of transformer secondaries impedance for a large transformer. I have seen this technique used elsewhere for audio power supplies.
The point in separate windings, bridges, and filter caps in the Spectral amp is to put the caps close to the output devices to minimize parasitic L and R between the filter caps and output transistors. Keith is one sharpest engineers I have ever met and doesn't do much stuff in the way of gimmicks. I have heard a direct microphone feed through one of the Spectral amps during a recording session in the Mort Meyerson Symphony Hall in Dallas and he must be doing something right........... :eek:
A simplified but similar technique is used by Steve McCormack who puts the filter caps next to the output devices.
http://www.mccormackaudio.com/index1.html |
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| Da5id4Vz |
| quote: | | A new company, McCormack Audio Corporation of Virginia, owned by Bill Conrad and Lew Johnson of Conrad-Johnson fame |
Golly, didnt expect to see that.
Never noticed the place all the times I drove by too. |
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| grataku |
| quote: | Originally posted by Fred Dieckmann
I believe that the point the guy explaining this to Lars was trying to make is that if attention is not paid to PCB and wiring impedance, the caps can very well have different ripple currents across them. One of the reasons for using multiple capacitors that each individual capacitor is not rated to carry a disproportionate share of the ripple current and that the ripple current is to be divided equally by the number of caps in parallel. This prolongs the life of the capacitors and is just good engineering. I have a feeling that it was the in the context of wiring and PCB impedances that this was presented.
|
Good reverse-thought-engineering Fred. ;)
Perfect example on how an innocent little correct explanation can get blown out of proportion in the the wrong hands. |
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| Christer |
Adding to what Fred just posted, you may have a look at the
two schematics I posted earlier in this thread. Seems like nobody
paid attention to them, being more interested in burgers and
the etymology of "whopper". I don't know if those solutions are
approved as good enough by Fred, though, and they are only
part of the solution, of course. Resistors between bridges and
caps etc. still useful, as also Fred pointed out. |
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| Lars Clausen |
A sweep test like this can give you a good qualitative assessment of a capacitor's sonic performance. Even in just one single capacitor there are large amounts of resonances, also in the audioband. With several caps in parallel, the resonances explode.
Another thing: A Black Gate VK has much lower resonances than a normal paper electrolytic cap. And sounds better too.
(Note the graphic below is drawn for illustrative purposes, not an actual measurement). |
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| D3 |
Lets get down to nitty gritty..........what is the best approach
sonically......................that won't be hugely expensive..............
most Aleph-X amps will probably be arround 100watt ..............
so typically what should be aimed for.............
so far it seems keep capacitors to highest quality but least number to do job.
use 2 rectifiers
D3 Bolton uk |
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| Petter |
I think this has been a useful thread. Thanks Claus!
Another point which has not been adressed is the fact that as you increase the capacitance of your PSU, you also significantly increase the current spikes in transformers and diodes while shortening the pulses. Some resistance will re-lengthen the pulses. Unless pulses are lenghtened, you need progressively bigger transformers to deliver the required current for the shorter pulses.
I have moved over to switched mode for these and other reasons.
Petter |
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| Lars Clausen |
| Just thought i'd show you some of the real measurements on capacitor resonance. First Black Gate VK 47 uF 160V. |
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| Lars Clausen |
| Second an OSCON 100uF 6.3V |
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| Lars Clausen |
And lastly an average 470 uF electrolytic capacitor.
These curves should speak for themselves. |
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| Fred Dieckmann |
"These curves should speak for themselves."
I guess they will have to with no scales or explanation. I have no idea of what I am looking at. Tell us the test conditions and the range and units of the X and Y graph axis. Volts? dBm? Hz? furlongs per fortnight? What exactly are we looking at..... |
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| Jocko Homo |
I don't see no stinking resonances.
Next time, try measuring the magnitude AND phase of the DUT, and showing the results in a polar plot.
And it might help to put a DC bias on a polarised cap.
What you claim to be a resonance on your drawing looks like noise, and the plots are not any more convincing. What exactly is is trying to illustrate?
I trust that you will have it sorted out by the time I return. I don't want to have to 'splain this again.
Yes, all caps have a self-resonant frequency, but this does not seem to be what you are trying to porve.
Jocko |
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| SY |
| quote: | Originally posted by Fred Dieckmann
"These curves should speak for themselves."
I guess they will have to with no scales or explanation. I have no idea of what I am looking at. Tell us the test conditions and the range and units of the X and Y graph axis. Volts? dBm? Hz? furlongs per fortnight? What exactly are we looking at..... |
Dammit, Fred, you beat me to it. |
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| pmkap |
Off Topic
Jocko,
Is that you in a Lotus Super 7? |
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| fdegrove |
Hi,
| quote: | | Is that you in a Lotus Super 7? |
Looks like a Caterham Lotus Super Seven to me but I don't think it's Jocko driving it...
Cheers, ;) |
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| Da5id4Vz |
| I think that’s Jocko driving a lotus in the open sequence "The Prisoner". |
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| Lars Clausen |
| Interesting reaction pattern .. :D |
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| Christer |
| quote: | Originally posted by Lars Clausen
Interesting reaction pattern .. :D |
Why? If you post diagrams with no explanation of what is
plotted you should expect people not to understand. I am
as puzzled as Fred, SY and probably everybody else. The
only interesting reaction is from Jocko, who seems to have
managed to decipher something out of the diagrams, despite
the lack of info. Maybe he has used the same software/equipment
as you, so he knows what to read out from the terribly
messy texts. |
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| Lars Clausen |
Christer: My remark about 'Interesting Reaction Pattern' is related to the fact that a few guys in here have the habit of changing the subject towards Hamburgers, yellow cars or whatever, when they can't think of something better to say.
My point is that capacitors have resonances, and paralleling capacitors directly will allow these resonances to increase significantly. The resonances are interactions of one capacitors's capacitive part with other's inductive parts, or what i have called Current Woppling. Maybe somebody dislike this word, and certainly some people in here also dislike the effect all together. But it's there, even for the people who are in denial of either its existance or significance.
So presenting evidence that my claim of current woppling is NOT 'mostly ****', as someone in this thread want to impress.
I must admit that 10 years ago i was out there promoting to parallel a number of smaller caps instead of using one big one.
A bunch of people from Scandinavia who are reading this thread can probably remember this.
But the people from Chemi Con (former Sprague) made me aware that maybe parallelling directly wasn't the best solution after all. A better way should be found. So we did the Virtual 4 Pole setup, where capacitor interaction is prevented by controlling the capacitor interaction with small resistances.
Now to an explanation of the curves:
The BLUE curve is the phase of the capacitor, 0deg. in the bottom, 180 deg. in the top, 36 deg. per div.
The GREY curve is the impedance 0 Ohm at the bottom, 1 Ohm at the top. The frequency span of this measurement is from 100 Hz to 5.000.000 Hz except for the 'normal 470uF cap' it spans in a higher resolution from 100.000 Hz to 1.000.000 Hz i'm sorry i don't have the same freq. span for that one like the other two. But i think the resonances are obvious just the same.
Anybody who is reading this thread can repeat the impedance part of this measurement using the simple setup presented earlier in the thread, and see for himself whether my claims concerning current woppling hold up or not. |
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| SY |
| I see the series inductance of two of the test caps (at RF frequencies), but other than that, I don't see any "resonances" there, just baseline noise. The "normal" cap shows zip below a megahertz, other than the same pretty random looking baseline noise. Could you explain to me what I'm missing? |
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| Lars Clausen |
| SY: Well maybe your 'Random Noise' is not just hiss from the input amplifier. Maybe it reveals that the capacitor has shifting phase response at shifting frequencies. In other words : Resonances. |
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| ScottRHinson |
| quote: | Originally posted by Lars Clausen
SY: Well maybe your 'Random Noise' is not just hiss from the input amplifier. Maybe it reveals that the capacitor has shifting phase response at shifting frequencies. In other words : Resonances. |
Lars,
I hate to say it, but that looks like noise to me too. I've measured the impedance of capacitors from audio frequencies, to several gigahertz all kinds. Any time I got a measurement like that it was either due to:
1. The impedance was too low for the meter to accurately measure. (Not paying attention to the dyanmic range of the instrument.)
2. The impedance was too high for the meter to accurately measure. (Not paying attention to the dyanmic range of the instrument.)
3. Bad connection.
4. Noisy signal generator.
Without knowing the makes, models and wiring of all of the instruments/dut in the test then it's hard to gain anything from the caps you posted.
Scott |
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| Lars Clausen |
Scott: When somebody stands up and actually presents documentation of something, and i dont mean this kind of 'documentation' :
'I have given considarable thought to it, and it doesnt matter'.
It's always easy for somebody to say:
I know all about this, and your results are wrong.
What is maybe a little harder, but a whole lot more interesting is: Can you present some kind of documentation to prove my measurements wrong? Since you have such vast experiences in this field, you probably have in your drawer some of your numerous measurements to show ? |
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| ScottRHinson |
| quote: | Originally posted by Lars Clausen
SY: Well maybe your 'Random Noise' is not just hiss from the input amplifier. Maybe it reveals that the capacitor has shifting phase response at shifting frequencies. In other words : Resonances. |
Also, without testing identical value, and voltage capacitors I'm not sure you can make a call on which one is "better".
Scott |
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| Lars Clausen |
Scott: I know what my measurements show, and what they mean in a real life Audio environment.
Whether you agree with my theory or not is really up to you.
I'm not trying to sell you these results, just want to show all you guys one way to improve your DIY amplifiers, by eliminating power supply resonances. And all it takes is a simple measurement with a Tone Generator, power amplifier and a MilliVolt Meter.
If you don't have access to these instruments, you can also avoid these resonances by taking a few precautions in your power supply design:
1..Don't parallel multible capacitors directly.
2..Use only the nessescary amount of uF, bigger is only better up to a certain level. How much is nessescary varies from amplifier to amplifier and i some amplifiers the loudspeaker load also becomes a factor for the power supply size. Can be found with listening tests.
3..If you have to parallel capacitors, do it intelligently, in a way to prevent the capacitors from interacting. The V4P scheme above is one way of doing it, there may very well be other ways too. |
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| ScottRHinson |
| quote: | Originally posted by Lars Clausen
Scott: When somebody stands up and actually presents documentation of something, and i dont mean this kind of 'documentation' :
'I have given considarable thought to it, and it doesnt matter'.
It's always easy for somebody to say:
I know all about this, and your results are wrong.
What is maybe a little harder, but a whole lot more interesting is: Can you present some kind of documentation to prove my measurements wrong? Since you have such vast experiences in this field, you probably have in your drawer some of your numerous measurements to show ? |
Lars,
I'm not sure why you've taken offense to my last post. I'm very interested in this thread and would like to quantify the issue you have brought up if it's possible. I apologize if you thought my tone was out of line, I certainly didn't mean my questions as an insult in any way. My sincerest apologies.
I have measurements that I can post when I can get back to my desk in San Antonio...which is an hour and a half away, unfortunately I won't be there until next week.
You've posted some measurements of impedance and phase of capacitors and are trying to post I don't know if these were taken with a Vector Network Analyzer or not, but I will assume for the time being that they were.
I don't know the following things from your post:
1. Drive level, how much signal were you using 0dBm? 0dBV? 0dBmV?
2. Test circuit, were you connected single ended to the S11 port of your instrument?
3. Calibration, cable zeroing? Did you have calibrated test loads of an open circuit, short circuit and some nominal impedance for the frequency range of the measurement. Were these devices used at the end leads of the test interface, eliminating impedance transformation from the test instrument leads?
The magnitude and phase posts you showed in your plots shows a lot of spikes in the phase portion (blue right?) The first cap is a 47uF Black Gate. The impedance is at the 4'th division from the bottom (counting the bottom as 1) The phase line is very clean.
The next two caps, 100uF and 470uF show the impedance to be almost at the bottom. If the bottom is 0 ohms and the top is 1 ohms, how come the black gate capacitor even has the trace on the screen at the 100Hz frequency. 1/(2*3.14*f*c) yields an impedance magnitude of 33 ohms. ~15 ohms for the 100uF and 3.4 ohms for the 470uF.
Now, if your instrument is measuring phase by comparing voltage and current at the output port, and using a PLL to lock on to them both it looks to me like your instrument is having a tough time with low impedances. In the second measurement, the magnitude starts to rise drastically about half way accross. When it goes above the second line, the phase line gets very clean. This indicates to me where the minimum impedance that the instrument can measure the phase between it's output voltage and current. Notice that the Black gate capacitor spends the entire measurement above that impedance point, so the phase can be accurately determined and doesn't show the noise. Notice that the 470uF cap spends the entire measurement below that impedance point, and the instrument is having trouble.
If you are driving a very low impedance the voltage on the output port will be limited because of the internal impedance of the instrument will limit output current. The instrument will then try to lock onto that low voltage, very often locking onto noise, and therefore the reason for the spikes in the phase response.
Scott |
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| SY |
What you're missing to show that this isn't random baseline noise is several replications, with all the peaks and valleys showing up in the same places to show that whatever phenomenon you're seeing, it's systematic. To do that properly, you need to connect and disconnect the caps for the replication runs.
Additionally, you need to show the same curves with n times as many averages; if the noise reduces by a factor of the square root of n, it's detector noise. If it doesn't, it's source noise of some sort; it might be "capacitor resonances", it might be something else, but at least you've eliminated half of the possibilities.
You also need to run true baselines with the same signal levels and number of averages so that the intrinsic baseline noise can be known.
You've made a start here, but I'd strongly suggest that you don't have nearly enough data for anyone to conclude that "capacitor resonances" are the source of the choppy-looking baseline. |
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| ScottRHinson |
| quote: | Originally posted by SY
You also need to run true baselines with the same signal levels and number of averages so that the intrinsic baseline noise can be known.
You've made a start here, but I'd strongly suggest that you don't have nearly enough data for anyone to conclude that "capacitor resonances" are the source of the choppy-looking baseline. |
Very good points. I agree completely.
Scott |
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| Lars Clausen |
Scott: Happy tone again :) Sorry, i did not make these measurements personally, so i really can't answer your questions. But you are right they were made with a Vector Network Analyser.
SY: Good points ... I am not sure about the noise floor of this analyser, so maybe it's better to take some measurements with another set of instruments where i know the noise floor. However it will only affect the ESR part, as i think the phase noise is not in conflict with any noise floor.
What i will do is go to my office and repeat the actual measurements i presented, and also find the noise floor of the instruments involved. This way i can also present documentation of the real claim here by taking similar measurements of parallelled caps to compare. |
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| SY |
Lars, thanks. Be aware that a phase plot will ALWAYS look spikier than the magnitude plot from which it's derived. That's because of the differentiation nature of their inter-relationship. This is a minimum-phase device, so the two are related by a simple derivative, i.e., the phase is proportional to the derivative of the magnitude with frequency. I won't say "Hilbert transform" because that sounds so geeky.
Even if you know the noise floor of an instrument, you still should be doing (at minimum) the sort of control runs that Scott and I have suggested. And be prepared to be disappointed if the data don't support your hypothesis; nature is unkind in that way all too often, as proved to me by the number of my own seemingly-wonderful ideas that have ended up in the trash bin. |
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| Lars Clausen |
Well i have to admit that with the instruments available on my workbench i have not been able to measure the effects i had hoped for, so far. The Chemicon's behave nicely through the entire audio band with low and stable ESR, and the problems don't start until way above the audio band. The resonances i have been able to measure did not seem to change significantly when parallelling several caps.
But in my setup (shown in this thread) i can only measure magnitude NOT phase continuance.
Also i don't have the network analyser at hand right now.
In the next few days i will try to rethink how i can measure the effects using normal benchtop instruments. Maybe it's possible to measure the current flow between two parallel capacitors without disrupting the high Q connection.
For now it's saturday night here in Denmark, and my favourite pub is calling ... Have a good saturday everyone :) |
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| Christer |
Lars, what is still not clear to me is if your goal is to minimize
the effect of mismatched capacitors or just bad PCB layout,
or both. |
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| fdegrove |
Hi,
The proof shown isn't proof but the point is well taken though...
Nothing new, but it would be nice to have some properly made graphs.
Lars?
Cheers,;) |
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| Kashmire |
Time to throw my hat into the ring. I’ve learned an immense amount of material over the past years, mostly from long-standing “experts” on the internet. For example, I have been an apprentice of Linkwitz in speaker design. In amplifier design, I have become a student of John Broskie, Steve Bench, Dr. Gizmo, Lynn Olsen, and Nelson Pass.
Each “master of the subject” has their own personal bias, and presents the apprentice with confounding and conflicting advice. One must pick and choose each opinion carefully. For example, combining Broskie’s hatred for noise, Pass’s desire for simplicity, and Olsen’s preference to coupling transformers.
Lars has some interesting ideas regarding capacitors, which he has back up with real data, which makes it worth looking at. I believe that Lynn Olsen also thinks a similar thing (Quote below from nutshellhifi regarding priorities in amplifier design. Interesting that Lynn chose filter capacitors to be the fifth most important priority):
| quote: |
5) Absence of rectifier switching noise. The noisiest circuits of all are solid-state bridges driving large values of electrolytic capacitors. (As found in almost all transistor gear and the DC supplies for heaters and filaments.)
The commutation noise of the diodes shock-excites the RLC of the stray L in the cap bank and the stray C in the power trans secondary. The resonance of this tank circuit is typically anywhere from 4 to 20KHz and the Q's are large, anywhere from 5 to 100, depending on the DCR of the caps. This is why paralleling large values of electrolytics with "better", faster polypropylenes can frequently result in worse sound. It is also the reason power cables are audible ... they act as antennas for the small Tesla coil that most power supplies resemble. The supply radiates noise into the chassis, the power supply B+ lines, the audio circuit, and the power cable. This broadband noise can be filtered and shielded (at considerable trouble), but it is much easier to eliminate the commutation switch-noise right at the source.
Choke-fed supplies are much quieter due to the choke slowing down the rate-of-charge of the main cap bank. I use a hybrid choke-fed/pi-filter to minimize the shock-excitation of the main PS choke (this tip from the Radiotron Designers Handbook, Fourth Edition).
|
Linkwitz http://www.linkwitzlab.com/
John Broskie http://www.tubecad.com/
Steve Bench http://members.aol.com/sbench102/aboutme.html
Dr. Harvey "Gizmo" Rosenberg http://www.meta-gizmo.com/Tri/index-1.html
Lynn Olsen http://www.nutshellhifi.com/triode1.html |
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| SY |
| quote: | | Lars has some interesting ideas regarding capacitors, which he has back up with real data, which makes it worth looking at. |
Lars himself admits (and kudos to him for this honesty and open-mindedness!) that the data may not be quite what it was claimed to be. |
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| Kashmire |
Ach! Why does one worry about current transients in a Class-A amplifier?
| quote: | | almost any large can capacitor will work very slowly, and play with a slow and out-of-beat bass |
Properly designed, the Class-A amplifier power supply would operate in steady-state. Low frequencies would not demand any more power than high frequencies. Therefore, why would the “speed” of a PSU capacitor matter?
The only reason capacitors are used in a Class-A amplifier is to filter out the rectified DC. This is usually 100Hz or 120Hz (corresponding to 50Hz and 60Hz line voltage). This is why “capacitor multipliers” work with Zen amplifiers. |
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| mrfeedback |
"I'm not trying to sell you these results, just want to show all you guys one way to improve your DIY amplifiers, by eliminating power supply resonances."
Hello Lars,
What kinds of subjective sonic improvements are you finding with your non/low resonance capacitor bank ?.
Eric. |
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| fdegrove |
Hi,
| quote: | | "I'm not trying to sell you these results, just want to show all you guys one way to improve your DIY amplifiers, by eliminating power supply resonances." |
Eliminating by //ing the same caps in //?
Nah...that won't work...
And before any brilliant geist comes up with another brilliant idea...Let's have a look before we flame it.
Resonance, tank resonace and ignorance.....
Good luck with it,;) |
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| Lars Clausen |
I just found the reason why my 2 hour attempt last saturday didn't give any usable measurements of current wobbling. I was looking the wrong place, by measuring the spectrum of the voltage resosnances across the terminals of the capacitor. However the point is that this is exactly where the current exchange products null themselves out, and so gives no usable result.
Right now i'm working on another project, but before too long i will device a usable test on how to measure and prove the existance of current wobbling. Then i will publish in this thread.
I know someone once said: 'I have made an
allowance for the actual existence of such a thing. I merely
dismiss it as not a real problem.'
However in this case we have found several years ago that it IS a real problem, in Audio Amplifiers, otherwise we would never have known about this effect in the first place.
I have described the effects soundwise earlier in this thread. Can be recreated by anyone.
After that we devised a solution to address the theoretical removal of current wobbling. (The V4P interconnection). And the solution worked. It solved the (audible) symptoms of the wobbling effect. Now we are working to also devise a test that will actually show the effect on instruments. May be a harder task to get a picture of the beast, but i think definitely worthwhile.
So i would say: We have established that it IS a real problem, we know (from one of the worlds greates capacitor makers) the thing exist, and we will eventually show you the hard evidence too. |
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| SY |
| Thanks, Lars. I greatly appreciate your efforts. I'd love to see what you turn up. |
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| ScottRHinson |
| quote: | Originally posted by SY
Thanks, Lars. I greatly appreciate your efforts. I'd love to see what you turn up. |
Yes, I'm looking forward to this too, I'm intrigued to see what the magnitude of the effect will be, and what frequencies it would happen at. |
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| ScottRHinson |
| quote: | Originally posted by Lars Clausen
So i would say: We have established that it IS a real problem, we know (from one of the worlds greates capacitor makers) the thing exist, and we will eventually show you the hard evidence too. |
If I remember correctly the manufacturer who alerted you to this was Sprague/Chemi-Con? Do you remember the power supply application they were targeting? By any chance was it the Telecom/Computer industry where there are much higher dI/dT demands placed on power supplies due to all of the high-speed logic and memory?
I've looked at the Chemi-Con site and could not quickly find any application notes. If anybody has a link to the paper, it would be appreciated.
Scott |
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| Nelson Pass |
| quote: | Originally posted by Lars Clausen
So i would say: We have established that it IS a real problem, we know (from one of the worlds greates capacitor makers) the thing exist, and we will eventually show you the hard evidence too. |
I haven't seen anything here that would change my mind,
and given that a subjective evaluation is the final word on the
subject (at least for me), it's going to be a difficult thing for you
to achieve.
As far as the graphs go, they look like noise spikes to me, but I
stand ready to be wrong, and not for the first time. :cool: |
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| Dyno |
Hello.
There is no doubt in my mind that a lot of people on this forum know a lot more than me, but I have modified my amp ( with: Sprague/Chemi-Con caps.) to use a V4P setup of the caps.
I have to tell that the amp. have been used daily fore nearly 3 years before this modyfication. So I think I know the sound of it by now.
What I did, was placing resistors, in the same way as shown in this tread.
Does it work? Yes Yes Yes! The amp is transformed into another league!
A lot bigger soundstage especialy to the back., no harsh sound at all. Voises more naturel. More dynamic , but also a lot nicer to the ears.
It`s really hard to stop listening, once You started!
My point is this: Why worry about ways of messuring it, try it out on an amp Yourself! It speaks for itself.
Best Regards: Dyno |
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| Nelson Pass |
It's entirely possible that if you used single resistors
with multiple caps that you would get the same sonic effect,
as they form nice RC filters and will have less noise as if
you gave each cap its own resistor. |
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| grataku |
Why measure it? Because understanding the phenomenon and being able to quantify it in a reproducible manner is the only way to make real progress.
I fear we'll never see any measurements that make any sense coming out of Mr. Clausen and that like NP says all that was discovered was the benefit of having a couple of dB lower noise in the PS. |
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| Christer |
I think it would also be useful to see the PCB/wiring layout of the
oriiginal solution and the new one with the resitors. Maybe the
problem is in rather there as, for instance, Fred suggested. |
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| Fred Dieckmann |
From:
http://www.panasonic.com/industrial...num_app_dne.pdf
1.4 Using Two or More Capacitors in Series
or Parallel
(1) Capacitors Connected in Parallel
The circuit resistance can closely approximate the
series resistance of the capacitor causing an
imbalance of ripple current loads w i t h in the
capacitors. Careful design of wiring methods can
minimize the possibility of excessive ripple currents
applied to a capacitor.
I agree that part of the beneficial effects are probably from reduction of peak charging current. The reverse recovery voltage is a function of the peak forward current of a rectifier. Dividing the charging currents equally between multiple caps seems to me to be a good idea for the standpoint of reliability and in terms of distortion and changing of capacitor ESR with heating. Resistances between the filter caps and a film bypass seem to be a good idea from the standpoint lowering the q of the resonant circuit from inductance of the filter caps and wiring or PCB inductance and the high Q film cap. Capacitor Q in circuit is becoming more important as capacitor ESR for electrolytics approaches a few milliohms. Filter capacitor noise voltages are reduced by averaging in a similar manner to paralleling voltage reference for lowest noise. This looks more like egineering than voodoo to me.To paraphrase the old joke, we know what it is and are merely quibbling over how much.
http://www.evox-rifa.com/europe/ele...ife_factors.htm |
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| Christer |
Seems I misunderstood your earlier posts, Fred, and you agree
with Lars here. |
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| Fred Dieckmann |
| A agree with there being merit to some of the technical issues outlined........ not to questionable explanations and measurements. Lars has possibly gone out on limb but that doesn't negate the capaciitor circuit considerations, just some of the explanations and measurements that have been put forward. Power design for audio is not nearly as straight forward as one might think. |
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| Agisthos |
| Instead of waiting for measurements to prove if this or that works why not build the 2 power supply variations and listen? |
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| Nelson Pass |
Speaking of measurements, I just went out to production
and used an rms AC voltmeter to measure the AC voltage
across one of 4 parallel supply capacitors and the voltage
loss between parallel terminals on a running X1000.
The number is about 100 to 1, meaning that the impedance
of the capacitor is about 100 times the impedance of the
connection. This tells me that the mismatching in sharing
between capacitors is about 1%. I don't consider that to be
significant. |
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| IanHarvey |
I've re-read the whole thread and still don't get a word of it.
So, we have a circuit with a number of small capacitors linked in series by leads of finite resistance. If the lead resistance gets too big, the impedance at the output will look more like that of the final capacitor, not all of them in parallel. Yes, no problems understanding that, but NP has measured this and (at least for him) this is a non-issue.
Next we have a picture of a "wave of charge" passing from capacitor to capacitor on each charging cycle. Yes, the voltage graphs look a bit like that. But note that it is not a wave in the technical sense of the word. Voltages in this sort of network do not obey the wave equation; you need an LC-based network for that, and this is not one of them. This means that thinking of a wave bouncing back and forth from end to end of this network is strictly fanciful. It won't happen in simulation, and I doubt you'll measure it in real life.
Supposing I'm wrong, can somebody please tell me what I will measure at the output of my power supply, with and without 'woppling'. Assume for now that if I can't measure it, I'm not interested in listening for it.
Cheers
IH |
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| Lars Clausen |
IanHarvey: It seems to me that you understand more than you give yourself credit for.
For now i will only add that you should not entirely think of your power supply as 'what you can measure at the output'. It would be like measuring the light coming in through a glass window.
The measured light may be the same but there is a lot of difference between looking at a junkyard or a mountain landscape outside.
In other words (according to my claim anyway) the amplifier not only sees how many Volts come out of your power supply, it 'looks inside' the power supply. Every aspect of the power supply may have an effect on the sound. Even if no difference can be seen in Volatge, Amperage, Impedance or Ripple.
After all in any un-bridged amplifier your speaker signal passes right through your power supply's capacitors. This effectively means the capacitor's impedances and resonances are in series with your speakers. |
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| mrfeedback |
To me looking at the circuit given by Lars is a standard rectifier bridge/capacitor supply feeding each of four capacitors via 0.1 ohm resistors.
The first capacitor is subject to the usual ringing excitations caused by the secondary inductance/capacitance values and diode switching behaviours.
The next stage is four RC shunt (damping/snubber) networks supplied in parallel, and each of these individual RC networks infact has the other three networks as additional RC networks.
The final four resistors and 22uF PP capacitor constitute further high frequency damping of the supply system.
All of these snubbing networks also constitute dampers for energy returning from reactive loads.
The series resistors will of course cause voltage drooping proportional to load current, but the resistor values shown would cause 1V drop at 20 Amperes and not any real issue - correct me if I am wrong.
This constitutes a pretty low, but not infinitely low impedence supply, that should have no ringing components caused by rectifier pulses, nor load variations nor load reflections.
For the sake of eight resistors in addition to the normal capacitance (except divided between five capacitors), this looks to me to be an effective way of building a totally non-resonant supply, and in my experience a 'quiet' supply pays very nice subjective sonic dividends in terms of clearness, control and non-reactiveness and harshnesses.
I have tried a standard supply with a same value capacitor and sub 1 ohm series resistor in parallel to provide damping/snubbing and this gave good result.
I expect Lars' more extensive solution is an exceptionally good one.
Nelson is correct in what he has measured, but this is not looking for supply resonances, and in any case this is probably of much less importance with his class A amplifiers.
Thinking about it, the output stage and speaker load constitute damping for a conventional supply, and this probably is a large part of class A subjective sound.
Eric. |
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| mrfeedback |
"Supposing I'm wrong, can somebody please tell me what I will measure at the output of my power supply, with and without 'woppling'. Assume for now that if I can't measure it, I'm not interested in listening for it."
A conventional supply when loaded will be Dc with a sawtooth on top, and additional noise and ringing caused by rectifier/primary ringing, and also load variations and energy returned from reactive loads.
Paralleling main supply capacitors can make this worse actually, as can adding lower value parallel capacitors.
The non-woppling supply ought to be pretty free of saw toothing, and ought to have no ringing.
Amplifier PSRR is not infinite, and providing a 'dead' supply makes for a 'quieter' and 'blacker' amplifier - ie lower THD, IMD and load sensitivity.
Eric. |
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| grataku |
| quote: | Originally posted by Lars Clausen
The measured light may be the same but there is a lot of difference between looking at a junkyard or a mountain landscape outside |
Oh Jeez! |
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| Nelson Pass |
| quote: | Originally posted by mrfeedback
The non-woppling supply ought to be pretty free of saw toothing, and ought to have no ringing. |
You can say the same thing of a single resistor feeding
parallel capacitors (an RC network)
I am officially checking out of this thread. Continue to
enjoy. :cool: |
|
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| fdegrove |
Hi,
| quote: | You can say the same thing of a single resistor feeding
parallel capacitors (an RC network) |
Yes indeed...
It's the exact same thing.
Cheers, ;) |
|
|
| mrfeedback |
| quote: | Originally posted by fdegrove
Hi,
Yes indeed...
It's the exact same thing.
Cheers, ;) |
Hi Frank....and Nelson........
I beg to differ that these are not quite the same thing.......
Directly paralleled capacitors do not have external damping between them, and are free to interact according to the parasitic characteristics of each.
This interaction can cause supply/circuit/load resonances that may or may not be present all the time, and may be transiently triggered by supply or circuit or load characteristics/parasitics, or all three.
Nelson is correct in that the first resistors constitute RC rolloff of secondary/rectifier (transient) excitation currents, but there is nothing to damp oscillations between the individual capacitors, and between the capacitors and the circuit and circuit load.
Lars' version pays attention to this, and this is what I am giving due credit for.
I think most of us have heard tonal/dynamic changes when main caps are paralleled with same value and type, and/or smaller value and different type.
I have heard both of these cases enable subjective sonic/dynamic improvements.
I have also heard both these cases cause subjective sonic/dynamic detriment, and I think this can be largely due to brief decaying resonances in the supply/circuit/load system.
To some ears this may provide subtle or not so subtle response and/or dynamic emphasis and extra 'liveliness', but my ears have long since grown tired of this kind of excitement, and this presents as artificial to me.
These artifacts can also be distinctly un-musical into the bargain, and this is where sonic troubles can start.
A single pair of large and 'dead' (relativlely high esr) caps can indeed be more sonically acceptable than an infinitely fast supply for these reasons.
Running class A by definition puts a big snubber across power supplies.
I did clearly say much earlier in this thread.......
"Ime, taming psu resonances is always a sonically good thing.
Eric."
These observations apply mostly to class B stages (line and/or power amp/reactive speaker) where there is more opportunity for abrupt current transitions to excite and/or sustain any electrical resonances in the system.
.......just some of my views and experiences for now........... :devilr:
Eric. |
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| janneman |
| quote: | Originally posted by Lars Clausen
I'm sorry Nelson, we didn't invent this phenomena, it was explained at a passive seminar by the norther European representative of Chemicon (Former Sprague) Capacitors factory.
Now it was back in 1991, so i'm sure the word woppling is not the right word he said, but the phenomena is real enough.
If you have say 5 capacitors in parallel, in a dual rail connection, where the rectifier is in one end, and the amplifier is in the other, and we decide the ESR of each capacitor is 10 milliOhms, and the connection resistance between each capacitor is 2 milliOhms.
Do you (Nelson Pass) dispute that the capacitor nearest to the rectifier is charged with the largest current (since it has only 10 mOhm ESR) , and the one furthest away is charged with only about half the current (since it has 20 mOhm as seen from the rectifier). Then when the charging spike is over, the charge rolls forward from the first capacitor to the last and attempts to equalize the charge over the entire bank. So each capacitor ends up having the same voltage. This is what i have (maybe wrong word) called current woppling. |
Sorry for coming in so late guys, missed the fun.
The above story assumes that the fact that there is different impedances to each cap, means they will initially charge differently. This is not the case. The charging current will predominantly be determined by the wiring resistance of the transformer secondary and the diode incremental impedance. That lot is MUCH more than a few milliohms. So, at the end of the charging cycle, ALL caps are at the same voltage or at least very, very nearly so.
And even if the effect would exist, it is a very long jump to the sound effects mentioned in the first posts.
I agree with Nelson, mostly ****.
Well, Lars, that's what you get from listening to someone who wants to sell more caps instead of doing your own thinking.
Cheer up.
Jan Didden |
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