BOSOZ R18, R19 function

Hi all,

Pass Balanced line stage is my first diyaudio project (even my first attempt to solder). I have completed stuffing the board (from audioexpress) and tested it. It was singing (I was excited) but I can't tell its quality yet because I used crappy amp and speaker (Lo-Fi). One question I want to ask is the function of R18 and R19 (221 ohm) at the input. I didn't include them because the board didn't have place for them. Can I simply omit them or they serve some beneficial function?

I have a 10K dual gang potentiometer and would like to put it at the output side although the article stated a 5K pot. I remember Nelson said that you can have some flexibility for the value of pot. Correct me if I'm wrong. By the way, I used single-ended for the time being.

Thank to Nelson for this simple and wonderful project. It really help a newbie like me to start diyaudio and the result is encouraging. Thanks to the diyaudio.com community for their constructive discussion and help too.:D

Wallace
 
Hi, Wallace

R18 and R19 are there to keep the output stage of whichever source you are using from seeing the zener diodes Z1/Z2 and Z3/Z4. If you don't use the zeners you most likely won't have any trouble without R18 and R19.

Incidentally if you use P1 and P2 for input trim, I would think you could also get by without R18 and R19.

Hope that helps,
Erik