P1 in BoSoZ

I have a problem with BoSoZ and hoping for someone to help me out, so I can finish this exiting project and finally get to listen to it.

Since I'm so stupid on basic electronics I can't figure out what R18 221R are used for and how to wire P1 and R18 at +IN if I don't use P1?

My setup is this:
- Unbalanced only, no use of -IN and -OUT
- P4 master volume with 5K Elma stepped attenuator
- 10 K lin. pot as balance control before P4.
like here: http://2bak.homepage.dk/bal.gif
- no use of P1 and P5

Instead of P1 I put a 10K resistor.
1. I guess I wire the 10K resistor between +IN and ground on the PCB?
1. Where to put R18 resistor? Between my input selector and +IN on the PCB? What is R18 used for?
2. Do I need to short Z1 to R18?
What else to do at +IN if I don't use the pot?

Hoping for someone of you experts out there to bear with me.
I would really appriciate some help.

Thanks
/Jan
 

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
R18 and R19 are to keep the source from seeing the
zener diodes when the pots are turned up all the way.

While I'm not really concerned about blowing out the
zeners, some sources will oscillate into a cable terminated
in a zener (there's a little tip to file away :) )

You can delete P1 and P2 if you like, and for that matter
you can delete the zeners and with them R18 and R19.

R13 and R14 will give the ground reference, and R7 and R8
will keep parasitic oscillation at bay.
 
Thanks Mr. Pass
I think I will keep the zeners and the protection to be on the safe side...
I was planning to do my input like on this drawing. Is this a correct replacement and wiring of P1, 10K ??

[IMGDEAD]http://2bak.homepage.dk/p1.gif[/IMGDEAD]

On the other hand - since I run unbalanced only - I have the option to use a P1 pot - besides input gain - as a balance control, with one single gang pot for each channel, thus being able to adjust left & right input seperately. Thus I can leave out my balance control at the output.
Is it not recommended to use two mono P1's as balance control ?

Wouldn't the latter be the best solution for me overall, running unbalanced? Thus I can control input gain and balance with P1 and use my (better quality) P4 as attenuator without having to put another pot in front of it as balance...
 

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
Certainly you can use P1 as a balance control.

If you are running single-ended input only, I suggest
that you terminate the unused input to ground. If you
are never going to run balanced, then get rid of all the
stuff on the unused input and simply run a 221 ohm
resistor from Gate to ground on the unused input.

Also, the 10K resistor is optional on the inputs - you
do not have to replace P1 with a resistor.