Hello guys! It´s been a while since my last build. Now that i get the 2n5457 and j201 i build a BSIAB2.
It´s Gaussmarkov layout. I have a couple of questions altough. First, when biasing Q3 i couldn´t hear any difference in a certain range of the trimpot, so i just leave it in 4.11V Second, if the Gain pot is all the way down i have no output. I have to raise it a little bit to start getting output. And third, there´s a lot of Gain yet in the minimium Gain settings (when i have output) so I have to control the amount of gain with the Guitar volume knob.
Here are the voltages:
Q1
D:9.09V
S:5.05V
G:4.36V
Q2
D:9.09V
S:4.6V
G:4.3V
Q3
D:4.11V
S:0.571V
G:0V
Q4
D:5.05V
S:0.329V
G:0V
Q5
D:4.6V
S:39.9mV
G:0V
(http://img233.imageshack.us/img233/1967/hpim1882.jpg)
(http://img11.imageshack.us/img11/9610/hpim1879.jpg)
Yeah that how its meant to be, if you want some output when gain is at zero then remove the pot connection that goes to ground and stick in a 10k resistor between the pot and ground connection. experiment with the resistor size, smaller will give less minimum volume but this resistor whatever size doesn't affect max gain .
I forgot to mention that i used a 470pF cap in series with a 560pF cap for the 250pF.
Quote from: rasco22862 on February 04, 2011, 05:10:34 PM
I forgot to mention that i used a 470pF cap in series with a 560pF cap for the 250pF.
That would be fine, that works out at 255p and a tiny bit. This cap at the input makes little or no diffeece to my ears, and no differece in the slightest to how the gain pot works.
Thanks. Are the voltages ok? And how can I lower the general gain to have a more gentle sweep with the gain pot?