Steve Bench cap "tests"

[dhaen]

Dielectric absorbtion & the perfect capacitor

We seem to be striving for the "perfect capacitor" with minimal absorbtion.
This might be a good plan for signal coupling where we want minimum loss.
What about decoupling?
Capacitors with great dielectric loss exist. These have been used for decoupling purposes in RF circuitry, and perform better than a "perfect capacitor" for the job. They turn the waste energy into heat rather than reflecting it back into the circuit.*
Maybe we should be thinking about bypassing our (slightly inductive) high value decouplers, not with PTFE, but cheap and lossy ceramics!

*Of course it depends which decoupling we are talking about. I was considering power rails. Cathode "decoupling" is probably a different can of worms, and will depend on the circuit.

 

[jan.didden]

Right on the dot, John!

Jan Didden

 

[fdegrove]

KNOW YOUR STUFF

Hi,

You're absolutely right with this John.

In my book knowing your components and using them where they do the best job is an important asset.
It gives you the key to a world of possibilities.

Cheers,

 

[Christer]

Re: NOT WANTING TO "SOUND" ABRASIVE.

Hi Christer,



Could be,but allow me to doubt it.

I can't help but notice that digital reproduction of musical content is still a very much evolving issue.

When it comes to measuring I'd rather stick with what I'm familiar with.

Go ahead with it if you like,I'm obviously biased.

Ciao,

Are you trying to tell me your eyes can read off an oscilloscope
trace with 16-bit accuracy????

 

[Joel]

If he can hear the diameter of wire used in the AC supply, I'm positive he can see micro-details.

 

[Joel]

Just kidding, of course.

 

[fdegrove]

NEITHER BLIND NOR DEAF

Hi,

Christer,

Are you trying to tell me your eyes can read off an oscilloscope

No,just telling you that I'm not geared up to do the measurements using a sound card.
In other words I'm not volunteering for what you asked to do.

I also think that the diagonal lines on the pics from SB's test are pretty obvious.
No eagle eyes needed for that.

Joel,

Now you are being abrasive.

Then again your credibility has already hit rockbottom.

Just kidding, of course.

Ciao,

 

[Christer]

Re: NEITHER BLIND NOR DEAF

I also think that the diagonal lines on the pics from SB's test are pretty obvious.
No eagle eyes needed for that.

But the point was to measure the effect at lower signal levels
where the non-linearity is obviously much smaller for many of
the caps and not clearly visible.

 

[Joel]

Re: NEITHER BLIND NOR DEAF

Then again your credibility has already hit rockbottom.

I never had any here!
The minute I said I didn't worship carbon composition, I was a dead man....

You would think coming up with something as ridiculous as a 71A monoblock would have garnered me much favor! - but paradoxically, no one seems to talk about SETs all that much in here either... weird.

 

[dhaen]

SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET

no one seems to talk about SETs all that much in here either... weird.

SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET

 

[Joel]

You're a bad boy John.

 

[fdegrove]

ALL SET?

Hi,

Never seen anything like it.

ROTFLMAO.

Joel,

The minute I said I didn't worship carbon composition, I was a dead man....

I don't think it was that at all.

Then again you don't have to believe any of us.

John,

You're killing me.

Cheers,

 

[fdegrove]

LEVELS OF ERROR

Hi Christer,

But the point was to measure the effect at lower signal levels

No,the test was done at higher signal levels to make it more visible.

Surely the same errors are still there at lower signal levels?

Cheers,

 

[dhaen]

Sorry about the SET outburst.I don't know what came over me
Joel, you really wouldn't want to hear me "spouting" about SET's...

Surely the same errors are still there at lower signal levels?

Frank,
I think that when we are looking for very small errors, it can be helpful to exaggerate them to make them visible.
Th problem occurs when the component is non-linear. Then the measurements may not be consistant.

 

[Christer]

Re: LEVELS OF ERROR

Hi Christer,



No,the test was done at higher signal levels to make it more visible.

Surely the same errors are still there at lower signal levels?

Cheers,

But the error itself is not linear as can be clearly seen in some
cases, eg. ceramics. Furthermore, for the better caps it is very
difficult to see the effect at all, so we cannot get any good
figures for the error by just looking at the scope pics. Perhaps
the theoretical models for DA are good, though, and it would be
better to get an estimate that way. I haven't looked into that
at all. Anyway, I think the whole point was to find measurable
effects to explain audible differences, not just to find that caps
can behave strangely at large signal levels.

 

[fdegrove]

NON LINEAR.

Hi,

Th problem occurs when the component is non-linear.

All the more reason not to use non linear components.
Not only are these not linear but they are also unpredictable with varying frequency and signal levels.

Then again we may use that as an advantage occasionally.
You said it John,I said it (hinted at it more likely) before you,once you know the kitchen you can start cooking.

Geeh,I start to sound like the Max Havelaar.

Cheers,

 

[dhaen]

All the more reason not to use non linear components

Chicken & egg problem.
How do we know until we test?

 

[fdegrove]

DESPERATE

Hi Christer,

Anyway, I think the whole point was to find measurable

Can anyone turn a pigs ear into a silk purse?

You don't see or believe the effect of a dielectric on the sound?
Or on the frequency response for that matter?
Admittedly way beyond the audiorange but what is the audioband for one person is not necessarily the sam for another.
Not to mention phase rotation with varying frequency etc ,etc,etc.

You do remember Jocko's remark that infamous day when we were quietly discussing the importance of cartridge loading and looking at "transmission line" theory?
Same thing here + the effect of DA.
Once you get the hang of it,it is not all that hard to understand really.

Cheers,

 

[fdegrove]

NO NEED TO.

Hi John,

How do we know until we test?

A lot of if can be found in the datasheets already.

In the PC world we even have an acronym for that:RTFM.

I don't want to be rude but enuff is enuff or as a famous Belgian politician once said:

"Trop c'est trop en te veel is te veel".

After all we know a thing or two about making compromises.

Cherio,

 

[Christer]

Re: DESPERATE

You don't see or believe the effect of a dielectric on the sound?
Or on the frequency response for that matter?

I certainly see why it may affect the sound. Whether I
believe it or not, well, I think we want to do better than just
believing. The more we know about why components sound
this way or that way, the easier it will be to design circuits.
There seems to be a correlation between DA and sonic
impressions. Some will be satisfied with this, others will want
better proof, like a statistical correlation. Perhaps it is not about
DA at all? Perhaps it is rather some yet unknown phenomenon
and understanding this phenomenon would help us design
even better capacitors.

For an individual it may be sufficient to make a change, like
replacing a cap, and convince oneself that it is an improvement.
If this individual thinks it sound better and is happy, then all
is well. If this individual tries to convince a lot of other people
that his/her experience is "the truth", then all is not so well
anymore. Collectively, for the DIY community and for the industry,
we want more knowledge than just "people say capacitor X
sounds better than capacitor Y". Some will be dissapointed by
such "research", either since it threatens to prove the "wrong"
thing, or because they feel it may take the magic out of their
exotic components once it is known why they are good.