Coupling capacitor questions

Is there a limit to how large an interstage coupling capacitor can be before it begins to degrade the sound quality? For example, if 100uf is the recommended value, would using 470uf change the sound in a negative way, assuming both values are high quality electrolyics?

There are different effects regarding 'lytic caps. First, they distort if they act as a high-pass filter, so you want your -3 dB to be down us much as you can -> use big caps.

On the other hand, bigger caps have higher leakage, so you might get to a point where bigger means scratchy pots and noisy switches.

There are some more subtile effects like DA, RF-pickup and series inductivity, which I think tend to get worse with bigger values. Although I must suspect that these are less important for coupling caps than for other applications.

If the coupling cap is inside a feedback loop, there is a good chance that you cannot change it's value without getting into sharp subsonic resonances.

As a rule of thumb, I try to choose the values such that my -3 dB point is below 1 Hz. There is usually no point in choosing a way-too-large value, better invest in a better brand. And use bipolar types where adequate.

Samuel

Well, here is the application:

http://headwize.com/images5/pell2.gif

This is one channel of a headphone applifier which I am building.

C3 - 100uf feeds the active current source (Q3,Q1).

The article,

http://headwize.com/projects/showfile.php?file=pellerano_prj.htm

recommends the use of high grade caps such as elna or rubycon.

I do have some 470uf elna cerafine. I do have 100uf nichicon UPW's as my other option for C3.

Thanks

Plug and play is quicker than this forum.

Found that out a while back.

But if your garage dosen't look like "Parts R Us", then advice can spare inventory.

thats good stuff Samuel;

I been in the process of recapping my board and for some reason my buss section sound like a transistor radio after the recap ... sux the funny thing is I didn't change the values of my Caps.. just replaced them with the same values and KZ series Nichicons but still sounds like crud. anyway sorry for the hijack