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electrolytic capacitors


Dave A

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Working on some KPT 100 and 200 crossovers and wanting to replace those old TI electrolytic caps. The problem I am having is the new Erse caps have just as high ESR as the 20 year old TI's do. Kind of sad really that 15 and 25uf new Erse caps are measuring at least .3+ ESR. Any suggestions for better ones? I have a hard time believing those Erse's are state of the art and no better than the old caps are.

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52 minutes ago, Dave A said:

Working on some KPT 100 and 200 crossovers and wanting to replace those old TI electrolytic caps. The problem I am having is the new Erse caps have just as high ESR as the 20 year old TI's do. Kind of sad really that 15 and 25uf new Erse caps are measuring at least .3+ ESR. Any suggestions for better ones? I have a hard time believing those Erse's are state of the art and no better than the old caps are.

 

Short of going to exotics, I've had good luck with the JB capacitors available here. Good quality, high Q, and not terribly expensive.

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1 hour ago, Dave A said:

Working on some KPT 100 and 200 crossovers and wanting to replace those old TI electrolytic caps. The problem I am having is the new Erse caps have just as high ESR as the 20 year old TI's do. Kind of sad really that 15 and 25uf new Erse caps are measuring at least .3+ ESR. Any suggestions for better ones? I have a hard time believing those Erse's are state of the art and no better than the old caps are.

 

Hey Dave, just curious why didn’t you use the Dayton’s for these?

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The basic chemistry of electrolytics has not changed in about 75 years, so there are various tolerances of 'lytics but at the end of the day, a lytic is a lytic is a lytic. . Solen polypropylenes are not expensive and sound just fine. 

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Here we go again with this horseshit.  A capacitor starts out at extremely high, approaching infinite, impedance at DC and it drops impedance as frequency goes up.  A 0.2 uF capacitor is only "down" to 40 ohms at 20kHz, so how the hell is that going to offer anything worthwhile to the signal content when used in a loudspeaker crossover?

 

0.02 uF is 400 ohms at 20kHz, and 0.01uF is 800 ohms!

 

Any signal getting through such small-value caps in series with the drivers is going to be several orders of dB below audibility, thus an utter waste of time and money.

 

https://www.allaboutcircuits.com/tools/capacitor-impedance-calculator/

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Jeff, I want you to fashion a setup where the bypass caps can instantly be switched into and out of the circuit.  You may use as much 8AWG mil-spec silver-plated wire as necessary, and as high-precision gold-plated-contact switches, too.  I'll then come and operate the switches while you listen.  I want to see you be able to detect change!

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I'm glad to see someone else take up the resistance (!) to the bypassing chimera. It's a legitimate concept from RF work that got cross-walked into POOGE when good film caps were scarce and expensive to hobbyists, and then got a life of its own. Replacing electrolytics in the signal path with good quality film caps does make a diff, but then the improvement hits a brick wall as the rest of the circuit, stacked component tolerances, the listening room, etc swamp out any measurable gains in quality..

 

The only legit audio frequency/speaker impedance bypass I know is using a cap to bypass a tweeter attenuator, to compensate for falling tweeter response. I'm using that on an attenuator for a Great Heil, and it not only flattens out the last octave but reduces the bobbles in the 5-10 KHz (9th octave) range as well. 

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On 3/13/2020 at 7:33 AM, Madman1 said:

 

Hey Dave, just curious why didn’t you use the Dayton’s for these?

It's pretty space restricted on that little PC board.

 

On 3/13/2020 at 8:03 AM, glens said:

Is your meter in proper calibration?

Yes and that calibration you mention would still show variance even if it was off. It shows the 20 year old TI's to measure the same as today's Erse's did.

 

20 hours ago, boom3 said:

The basic chemistry of electrolytics has not changed in about 75 years, so there are various tolerances of 'lytics but at the end of the day, a lytic is a lytic is a lytic. . Solen polypropylenes are not expensive and sound just fine. 

Yes and I am looking for a good tolerance electrolytic that beats the 20 year old ones. I need the smaller size here if I can find something worthwhile.

 

13 hours ago, boom3 said:

The four lead box looks good for a PCB based crossover. 

OK could you tell me what that means?

 

10 hours ago, Jeffrey D. Medwin said:

 

Bypass EACH of the basic larger value WIMA MKP4s with a 0.22uF FKP1 WIMA at 1250 VDC, a 0.022 uF FKP1 at 1250 VDC , and a WIMA  FKP2 0.01 at 630 VDC, and P.M. me as to what it sounds like to you !!  You'll fall in love, I bet !!   SHORT lead lengths.

I think I will pass on that.

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1 hour ago, Jeffrey D. Medwin said:

See photo. I will NOT build stereo amps, henceforth, because its too crowded, and impossible to easily work on, when the needed-as-ascertained-by-EAR film bypass caps are added.

 

Do you not realize that overheating capacitors by excessive soldering changes their electrical characteristics? If you're hearing any difference at all, that may very well be the cause of it. It's certainly a more plausible explanation than magic.

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Jeff, say you've got only a 25 uF cap in series with an 8 Ohm driver.  At 800 Hz that cap presents an impedance of 8 Ohms, so that would be the crossover frequency (800 Hz) of your first-order crossover.

 

Staying with that cap alone, if the driver was 16 Ohms, the crossover frequency would be 400 Hz, and 1600 Hz for a 4 Ohm driver.  See where this is going?

 

Parallel caps result in increased total capacitance, with the result that the impedance will be lower at any given frequency.

 

Let's do some math.  Using two parallel caps, one each 25 uF and 0.2 uF.  The 25 alone is 8.0 Ohms at 795.77 Hz and together (25.2 uF), 8.0 Ohms occurs at 789.46 Hz.  That's a fairly negligible lowering of the crossover frequency, but that change may be discernible by a well-trained ear.

 

I understand that you'd use the value of 0.2 uF to sweeten a specific range of frequencies, though I forget just where that was.  Let's see what's going on at 2500 Hz with this pair of caps.

 

At 2500 Hz they act as parallel resistors of 2.546 Ohms and 318.310 Ohms, for a total of 2.526 Ohms.  The contribution of the lower value (the larger cap) represents 99.206% and that of the higher resistance value (the smaller cap) represents 0.794% of the signal passing through to the driver.  That is: -0.069 dB through the large cap and -42.004 dB through the small cap.

 

The bypass cap is obviously not contributing anything meaningfully at 2500 Hz!  And the ratio stays the same at 15 kHz, so I'll assume it's also the same at 1 kHz.  And that's with the largest bypass value you suggested.  Obviously the even-smaller caps' contribution will be even smaller.

 

40 dB down from the main signal has got to be inaudible no matter how highly-resolving a system is!

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31 minutes ago, Jeffrey D. Medwin said:

I am not overheating capacitors !! 

 

Ah! Your reponse is so emphatic that you must have implemented procedures and tests to make absolutely certain that you are not overheating while soldering. We have to document that where I work. Why don't you tell us all what your procedures were, and the results of your tests?

 

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You are grasping at straws.  Its not magic.

 

If it's not magic, then there must be a logical explanation for it. What is that explanation? Do you even have a theory?

 

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Proper multiple film bypassing is THE state of the art, and only one or people in this world even know how to do it well, really well.

 

Oh, I see ... it's a secret that only special people get to know. How were you chosen for this privileged role in life? Does it involve a deity?

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4 minutes ago, Jeffrey D. Medwin said:

No need to answer any of your questions !! 

 

Oh, there's definitely a need for my questions to be answered. Extraordinary claims require extraordinary evidence. Of course, nobody is forcing you to answer them, which means that everyone else will answer them for themselves.

 

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You are far too combative.

 

How much would I have to turn down my combativeness for you to answer my questions?

 

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Do what YOU want to do, and I will DO what I want to do.

 

Believe me, I shall. You are welcome to do the same.

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1 hour ago, Jeffrey D. Medwin said:

Proper multiple film bypassing is THE state of the art, and only one or two people in this world even know how to do it well, really well.

Are you one of them?  Who is?

 

That soldering quality is all over the map, in my opinion.  Since you claim to hear one bad inch of wire, have you considered how solder might affect the sound?

 

Also, @Edgar is correct, once again, in my opinion.  Your connections to those film caps are multiple, and are right at the capacitor body.  There isn't room for a temporary spring-loaded heat sink, so how are you not excessively heating the capacitor?

 

 

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So just wire these in series with one or all the the existing capacitors? I am not asking for help to build an amp here but just for a crossover. You mentioned that this crossover was to complicated and you did not build them that way. How would you simplify it?

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