Ignorant capacitor question....

[OO1]

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[Edgar]

16 minutes ago, Randyh said:

Cheng Shin  make all kinds of tires , their bicycle tires are dangerous in the wet or rain  

 

Side story:

 

Years ago, while riding my bicycle past a golf course (not Cheng Shin -- Avocet FasGrip), I thought to myself, "Look at those crazy golfers. They don't even have enough sense to come in out of the rain." The irony of that statement didn't occur to me until I was several miles down the road.

[Coytee]

2 minutes ago, Edgar said:

 

Side story:

 

Years ago, while riding my bicycle past a golf course (not Cheng Shin -- Avocet FasGrip), I thought to myself, "Look at those crazy golfers. They don't even have enough sense to come in out of the rain." The irony of that statement didn't occur to me until I was several miles down the road.

 

[OO1]

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[glens]

1 hour ago, Coytee said:

To me, the capacitor, chokes and various parts....  are voodoo.  I "get" what it does.  What I don't get is having the same spec item (caps in this case) but one of those caps is generic, one is "esoteric" but again, same values....  what is different?  Does one allow a cleaner bass (or trebel) signal to pass through?  Is the signal more "pure"....  in a side by side what is the end user going to experience to justify whatever his purchase is?

 

Better materials make for a better chance of better linear behavior throughout the usable spectrum over a greater length of time.  But lesser parts would be preferred if there was more attention to detail in their assembly and you could only have one or the other.  That's the way I see it.

 

I'm sure the caps in my Forte IIIs aren't the best-made available but they're working well enough at the moment.  In fact, the only time I ever think about it is when reading posts here...

[seti]

7 hours ago, Randyh said:

where do you buy them

 

There are a few ebay sellers in Moldavia and Ukraine. Caps are cheap but shipping is high. I order different values once a month. I have a good stash now.

 

 

 

[OO1]

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[seti]

1 minute ago, Randyh said:

I have seen a box   full of these  lately in a Military surplus --------I was not sure if they were any good since I didn't have my ESR meter , but I'm going back ---

 

They k75 are metal tubes with glass seals. Not sure what can go wrong lol..... The k71 polystyrenes had date codes from the early 80's.

 

ESR is on my list of things to buy. I do have an oscope setup as a curve tracer. If they are really resistive the 0 tends to lean...

 

 

[Edgar]

DATS (Parts Express) measures ESR, and a whole bunch of other useful things.

[pzannucci]

On 4/16/2020 at 6:32 AM, Coytee said:

As you likely know, I use an active....  however, I DO have passives on my LaScalas but the twist is, none of what I own creates this question in me.  It just dawned on me and I'm a curious type.

 

So, if a capacitor helps to block low frequencies, if it's doing its job correctly then you won't hear "X" frequency.  (by the way, if I'm backwards a bit on the capacitor, my question still applies to it for whatever it does)

 

Back to question....  if it's doing its job correctly, then it will block the low frequencies and "you won't  hear them".  Now, let's change the grade of capacitor from an entry brand to an esoteric " high quality" (high price) variant....  if it blocks the same frequencies and you still "don't hear them" then what is the improvement the higher quality unit gives you?  

 

Not trying to start any issues.....but with this Covid in our air, we could perhaps use a good thread or two on tubes/SS, passive/active....  

 

It is however, a genuine curious question I have....  if I successfully block "X" frequencies, then what improvement does a fancier version bring to my table?  How does it block those signals better?  Doesn't blocked equal blocked?  (not to be confused with calling me a blockhead)

 

I would like your report to be two pages, double spaced and presented in the third person.  

The key is "you kind of" block certain frequencies.  Really it will be a roll off based on the impedance and "actual" cap value/esr. 

 

Now for the other portion of the frequency range THAT IS NOT BLOCKED.  The capacitor will lend it's own "COLOR" to the sound depending on it's design.  The matching of the capacitor to what you like to hear and quality will determine which you should use.  Some of the boutique capacitors are supposed to be wonderful since you can hear every last drop of sound but to some old folks, that will make the sound, depending on the driver and crossover point, sound strident.  It is really just to each their own.  Really that simple even with COVID on the brain.

[JohnA]

Actually, I was trying not to denigrate a particular brand as cheap and poor performing.  Some of Cheng Shen's motorcycle tires are satisfactory to riders I know, that consider price important.  Maybe I should have used "Hop Sing" or "Kwan Do". 

[JohnA]

 

23 hours ago, Edgar said:

 

Side story:

 

Years ago, while riding my bicycle past a golf course (not Cheng Shin -- Avocet FasGrip), I thought to myself, "Look at those crazy golfers. They don't even have enough sense to come in out of the rain." The irony of that statement didn't occur to me until I was several miles down the road.

 

Years ago I made a similar comment, loudly, about golfers during the Hotter'N'Hell 100 as I rode by on my bike.  The Temp was 111F.  They didn't react that I could tell.

 

[JohnA]

On 4/16/2020 at 1:51 PM, Coytee said:

 

So that would allow the door to "close faster" on the sound/signal?  (it would be similar to a sharper slope in that it silences the signal before the slower one??)

 

 

 

No.  Resistance doesn't "slow" anything.  It just robs some voltage and current from the output of the capacitor (converting it to heat).  But the ESR might not be the same at all frequencies adding flaws to the passing signal.

[Edgar]

18 minutes ago, JohnA said:

 

Years ago I made a similar comment, loudly, about golfers during the Hotter'N'Hell 100 as I rode by on my bike.  The Temp was 111F.  They didn't react that I could tell.

 

 

Hottest I ever rode was 108°, near Sacramento. I emptied both water bottles within ten miles, had enough sense to turn around, and had to ride back without any water.

Oh, to be young and stupid again.

[Schu]

On 4/16/2020 at 8:14 AM, Coytee said:

You all need to dumb it down a bit...

 

 

 

My door is on hinges.  They allow my door to swing shut.  Once it's shut.....it's shut.   At that time, I don't care if my hinges are brass, copper, gold or anything else as regardless of their finish, they did their job of closing the door.  A different finish didn't close the door any faster or tighter....  they simply allowed it to swing closed.

 

Go figure.

 

 

It's ironic that you use this analogy... because some doors are more secure than others... some doors LEAK, and some doors seal tightly... some doors are hand built and are beautiful, and some doors are mass produced and cost effective.

 

If we take into account the idea that a door is a door and once shuts, works... then buy what ever door you want, They all work.

 

This seems to be more of an analogy of ECONOMICS,  and not one of performance or capacitor design/build.

[mboxler]

Another way to look at it...

 

The two rooms are the two capacitor plates.
The wall between them is the dielectric.

 

Ideally, the door between the rooms is so small that everyone (the current) will need to go through the hallway (the circuit) to get to the other room (the other plate). 

In reality, some people do get through the small door (leakage current).

 

Sorry...only door analogy I could come up with.

[MechEngVic]

The most expensive part of a capacitor is the winding process. Cheap mass produced caps are wound in fractions of a second, canned and coated in not much longer, by machines that do basic tension control. No attention is paid to the cap ends. Production runs are batch-tested and sold in huge numbers for next to nothing per unit. A high-end capacitor is usually wound by semi-automated, hand operated machines with precision starting tension control, tension monitoring throughout the winding process, and a special process to finish the outer windings. Special treatments are applied to the cap ends to help prevent unwanted effects. Of course, higher quality materials are used.

 

The purpose of manufacturing a high end audio cap is to "build in" a certain sound signature, and more importantly, to maintain it consistently. A properly wound, evenly tensioned cap will measure more consistently throughout its range of operation. If you've ever measured caps in general, you know they can be all over the place depending on the voltages and currents applied, their temperature, and even the length of their leads!

 

https://www.youtube.com/results?search_query=arizona+capacitor

[MechEngVic]

On 4/16/2020 at 4:32 AM, Coytee said:

So, if a capacitor helps to block low frequencies, if it's doing its job correctly then you won't hear "X" frequency.  (by the way, if I'm backwards a bit on the capacitor, my question still applies to it for whatever it does)

 

Back to question....  if it's doing its job correctly, then it will block the low frequencies and "you won't  hear them".  Now, let's change the grade of capacitor from an entry brand to an esoteric " high quality" (high price) variant....  if it blocks the same frequencies and you still "don't hear them" then what is the improvement the higher quality unit gives you?  

A capacitor in series with a load is called a "high pass filter", so instead of thinking of a cap as something that blocks low frequencies, think of it as something that passes high frequencies. As the frequency gets lower, it passes with less and less "volume" (higher impedance).

 

In passive crossover circuits, we are really only concerned with the frequencies between 20-20,000Hz. Your amplifier has taken care of the DC current, so a passive crossover doesn't see any DC under normal operation.

 

Think of a capacitor as an AC resistor that increases in impedance (AC resistance) as the frequency decreases, and decreases in impedance as the frequency increases. Think of a cap's charge as the current (although they are related, they are not the same, this is just for comparison), then you can compare its action to Ohm's law for voltage. In a cap, as frequency increases, resistance decreases, and Ohm's law says that makes current increase. As frequency decreases, resistance increases, current decreases.  Consider voltage constant:  R x I = V,   I = V/R,   (R-, I+),   (R+, I-),  (just for explanation's sake as a musical signal's voltage is constantly changing).

 

Then consider the capacitance formula:  C = Q/V   C=capacitance, Q=charge (related to current), V=voltage. You can see that at constant capacitance, as charge increases, voltage increases, and as charge decreases, voltage decreases. So it does go along with Ohm's law if you understand the relationship between charge and current. A moving charge creates current flow, so as a cap discharges it sends current to the load, then it draws current from the supply signal to recharge.

 

Now when you consider this higher frequency/higher current/charge, lower frequency/lower current/charge signal going to an 8ohm load tweeter, you're talking about higher voltage as frequency increases, and a lower voltage as frequency decreases across the tweeter. At very low frequencies, the tweeter sees the cap as purely resistive, and at very high frequencies, the tweeter sees the capacitor as a short circuit.