dude

Don't finish your stocks yet!!

leave some for me!!

I'm still in the middle of completing the list. darn!

HOLY SHIT, posted on my birthday and i do not know!!

Deserves a bump and a super praise!!!You're an epic winrar!!

Seeing what you just did there, i really want to try some class A biasing and start modifying my EMU1212M, but sayang lah!!

The opamp board is home etched? Looks great!

Najmods,

One problem with your mod.

The caps should be mounted at the bottom at the PCB with shortest leads as possible. The way you're doing it wastes capacitance and adds uneccessary impedance (hence more noise). Proper bypassing mod should be done under the board or under the socket if you're good enough.

EDIT: Why am i replying to a content months ago? LOL.

Anyway nice mod bro. Personally I'm too lazy to do caps mod for my equipments.

This post has been edited by LittleGhost: Sep 15 2008, 04:08 PM

paralleling small cap to big cap isnt really a bypass. That's a failed bypass imo.

Bypassing should be done CLOSE to the circuit, NEXT to the pins. This is to get low impedance for high frequencies as much as possible while avoiding lead inductance and noise pickup.

Bypassing is also done for signals in the signal path because electrolytics simply arent low enough impedance for higher frequencies.

EDIT: Bypassing for power supply is better known as decoupling.

This post has been edited by LittleGhost: Oct 26 2008, 11:14 PM

Firstly, just "paralleling small caps to big caps is a failed bypass". Simply put, it's not enough to just "parallel them" alone. You have to make sure the smaller bypass (decoupling) caps are close enough to the main circuit such as the OPAMP.

This is so that you give as low as possible impedance over a larger frequency of AC.

Smaller film caps and other variants have a lower impedance at much higher frequencies comparing to big electrolytics. This is why we parallel them. Of course ideally if we have huge capacitance values of film caps we'll ditch electrolytics completely. However this is not the case and we still need electrolytics because they offer huge capacitance on a much smaller footprint.


Looking at the pictures, only one thing to complain, LEADS TOO LONG. Not only you raise impedance but you also increase the susceptibility to magnetic field induced noise. So honestly don't follow whatever that guy did and if you want to make sure the leads are much shorter.



Bypass caps just use whatever you see fit. I normally just use a maximum of three stages of caps. Silver micas are VERY good but they are usually too small in capacitance. I only use Silver Micas for the signal path usually for limiting bandwidth. As for power supply decoupling, my favourites are Metal Polyesters, Metal Polyproplenes, Ceramics (X7R, C0G/NP0 grade), and good quality Tantalums. I usually use ceramics and tantalums paralleled to electrolytics these days due to space constraint. Another good configuration would be metal Polyproelenes paralleled to electrolytics. The idea is to parallel these type of caps to electrolytics and yet make them very close to the main circuit that you're decoupling. The type of configurations is up to your tastes and depends on the circuit you're trying to decouple.