[Sal]

I know how tough it can be selecting the right capacitors, I spent a few hours myself browsing Digikey's catalog selecting just the right caps for my next projects. You really have to look at the voltage, capacitance and size numbers carefully to find the right part.

I ended up choosing the Panasonic FM series over the FC series only beacause they are indicated as having lower impeadance than the FC series and slightly longer life. I can't say that it would make much difference, but all other things being equal, why not go with the better specs? It's only pennies per piece difference anyway.

Also, the data sheet for the OPA2132PA indicates that it is a FET input op-amp. The OPA2227PA is just listed as a high-precision, low noise op-amp. I am assuming it is not a FET input device? I don't know if it makes musch difference regardless, afterall, how it sounds is what we really care about right?

 

[Factor]

I did go for better cap specs when practical but I was also very focused on size, since I may end up wanting to use dual 9V's with this. That's why I went with the .18µF caps instead of .27µF.

What does FET mean, and how is it relevant to me building this amp?

And what about the 2227PA vs. the 2227P? Is there any reason why I should hold out for the premium version (currently out of stock), or is the PA version effectively the same?

 

[Sal]

FET = field effect transistor. It's just a different type of transistor used inside the opamp. The FET input opamps have a slightly different sound, but whether they are better or worse, is subjective.

I would think that the PA version is perfectly suitable for a CMOY amp and since you're using an IC socket, you can easily swap out the opamp at a later time. That would be what people refer to as 'opamp rolling'.

 

[einolu]

i thought cmoys had to use .1 uf caps. can somebody explain what difference the cap size makes (I know the ones in the powersupply add more "punch", but what about the ones in the audio circuit)?