[aych]

Wondering if anyone knew the sonic difference in exchanging current capacitors for ones with a higher farend rating?

thanks

 

[AudioCats]

same capacity but faster caps will give you better bass definition hence better feel of bass, while large (super large, such as 12000uF for headphone amps) but slow generic electrolytic will give you supper fluffy, boomy bass...... All depends on what you prefer

 

[amphead]

Yes, there is a point where you lose sonic definition and end up with inferior sound quality as you go large with your caps.

 

[J.D.N]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif same capacity but faster caps will give you better bass definition hence better feel of bass, while large (super large, such as 12000uF for headphone amps) but slow generic electrolytic will give you supper fluffy, boomy bass...... All depends on what you prefer

Sorry, i might be miss-understanding something here, but what do you mean by faster caps?

 

[Jambo]

Probably means low ESR, but I'm also a bit mistified by this thread. Did the o/p mean "Farrad" rather than "farend"?

 

[ericj]

esr is one rating, maximum surge rating is another important rating. farads aren't everything.

 

[JeffL]

Well it depends on the context of the capacitor too. You can't just go around putting large capacitors everywhere. For example, filter capacitors are precisely tuned, and if you change the value of the cap, you change the filter characteristics.

 

[aych]

so where do these cap replacements typically occur. Because it seems like many ipod's get modified with "black caps" are those just faster or bigger?

 

[JeffL]

Typically people remove or replace decoupling capacitors. Also, power supply reservoir capacitors may be increased in value for better ripple rejection.

 

[jsmithepa]

Am dying to know too... WHAT'S FASTER CAPS? Never learned that in electronics school!

 

[philodox]

Generally, from what I understand, in the signal path, you want the lowest value that will work for the application and not roll off the bass too much. Choosing a smaller value high quality cap [film] in these instances is preferable. In power supplies, having a higher value cap can sometimes be beneficial as it gives a larger reservoir for the power to stabilize. Or at least that is how I understand things from a completely non technical point of view.

 

[Pars]

Quote:

Originally Posted by jsmithepa /img/forum/go_quote.gif Am dying to know too... WHAT'S FASTER CAPS? Never learned that in electronics school!

Slew rate or pulse slope (dV/dT) is a spec applied to film caps that I don't see in electrolytic datasheets. Normally specified in V/uS. Not sure why electrolytics don't specify this (at least the ones I looked at, Pana FM), unless they are so slow that it would be ludicrous? Blackgates, etc. it is hard to find any specs on... just marketing fluff.

 

[kipman725]

Quote:

Originally Posted by jsmithepa /img/forum/go_quote.gif Am dying to know too... WHAT'S FASTER CAPS? Never learned that in electronics school!

bolocks hi-fi phrase that means nothing just nod and smile

just build amplifiers so they have a high common mode rejection ratio by using a difirential input and then you no longer have the problems with 60Hz ripple and you can get rid of those huge capacitor banks. As the common mode rejection has shot up to massive levels Brute force is not the answer for a headphone amplifier :|

 

[JeffL]

It has to do with the time constant of the realistic model of a capacitor. This realistic model of a capacitor is the model of the parasitic complex impedances which are present in electronic devices.

The model for a capacitor looks like this:

R_ESR is the equivalent series resistance of the capacitor.
L_ESL is the equivalent inductance.
R_Leakage is the leakage resistance.

L_ESL is the inductance due to the leads on the capacitor. They may not be very long, very thick, or look like what you might believe to be a capacitor, but they do in fact have capacitance. In certain applications this is very important. Generally speaking, this is why you want the leads of your capacitors short and thick, and you want to place them as close to the component needing the capacitor as possible. The reactance of the capacitor is cancelled out by L_ESL, so for small value capacitors for instance, this plays a significant role.

R_Leakage is due to the inherent loss of the capacitor material. Put it this way, a capacitor is not a perfect device, it leaks. A capacitor will in fact pass a small DC current when placed in series in a DC circuit, but for the most part this is negligible.

R_ESR is the equivalent resistance of the capacitor of all elements in series with the capacitor. The leads will have a small resistance, due to their finite width. As current flows in a circuit, resistance will impede it's flow. No material is a perfect conductor, and will have a certain per unit resistance. Additionally, one can take into account the resistance of the connection between the leads and the capacitor plates.

Now, back to the time constant. For a simple RC circuit, the time constant Tau is R multiplied by C, where R is the resistance in series with the capacitor, and C is the value of the capacitor. A large value of Tau means the circuit is slower to charge and discharge the stored energy in the capacitor.

Now take the realistic model of a capacitor: What do you have? That's right, a very simple RC circuit! So a capacitor with a lower R_ESR will have a faster response to a change in the voltage: It will charge and discharge into the circuit faster than a capacitor with a larger R_ESR.

 

[NelsonVandal]

Have any of you actually done a blind test with power caps? Or have you tried add/remove them live? I have, and I couldn't for my life tell the difference in an amp with active ground channel.