Orman buffer/Vr question

[m_charles]

Hi!
Thought this would be an easy one to answer, but after searching the archives for an hour, I'm still lost so...

I'm trying to put a JFET (J201) buffer in front of a Big Muff Tri clone. I built the buffer using Jack's buffer article. http://www.muzique.com/lab/buffers.htm

I'm trying to build the second jfet buffer pic down (on the site), the one that doesn't take the 1M biasing resistor to ground, but takes it to the "Vr".

The Vr, I understand to be Voltage Ref. usually 4.5V. Now on a Big Muff, would the collector of Q1, Q2, or Q3 be a good place to tap the Vr?
Or am I totally missing the point in regards to Vr?

My voltages on the muff are around: Q1 3.1V (lower than all the others) then almost 4.5V for Q2 and Q3.

Again, is one of the a good place to tap for the buffer's Vr?

thanks in advance!

chuck

[Minion]

VR is usually Created by useing a Voltage divider to get 4.5v, take 2 say 33k resistors in series between +v and Ground and were the 2 resistors meet is VR...The very first Pic on the site you posted shows how to create a VR....

[Mark Hammer]

Vr can be a bunch of different values, but typically it is as close to 1/2 the supply voltage as you can get with 5% resistors; the idea being that if you can't have a circuit with a +/-9v supply, the least you can do is have a +/-4.5v supply.

Occasionally, Vr will be something other than V+/2.  For instance, in the John Hollis Zombie Chorus, Vr is set to something like 6V, so as to provide a usable bias voltage for a delay chip.

[m_charles]

thanks guys.

So my idea of getting the Vr, directly off the effect's board, collector (in the case of a bjt tranny) is not something normally done in this sort of situation?

[Minion]

I might be wrong but I don"t think takeing the Bias voltage from the Collector is a good idea ,For one it could Draw the Bias current from the collector which might screw the Bias of the BJT Transistor...I believe the 2 resistor method is yer best bet.....