TL072CN Input Biasing

[axeman010]

HI All
I am trying to build the John Hollis Omnidrive 
http://www.hollis.co.uk/john/omnidrive.jpg
as a learning project and have discovered a problem. With the 100K Biasing resistor connected to the virtual Earth (4.5V) and to pin 5 of the TL072CN Omp amp (reading at pin 5 = 3.89V) I get very distorted output as soon as the gain  is turned up slightly. In fact is more like Fuzz. With e biasing resistor removed the distortion is more controllable and does not sound like fuzz

Reading the Tech Data for this chip it would appear that 3.89V as a bias should not give any problems.

Please could anybody suggest why this problem might be happening?

Many thanks

Axeman.

[R.G.]

Is it possible that that's not ALL that's happening?

[axeman010]

Hi  R.G

I have tried to simplify the circuit and have disconnected boost and the Octave part from circuit to discover the problem.
Therefore I have taken the output of from Pin 1 of the first Omp amp to to pin % of the distortion Omp amp. Without the biasing resistor its fine
with it its horrible !

Many thanks

Axeman

[axeman010]

Sorry that should have said pin 5 and not pin % ---- Oooopppssss