1
\$\begingroup\$

I added an Baxandall active tone circuit to an existing overdrive circuit and I'm having an issue. The signal passes through the circuit/opamp and out to my volume control but the bass and treble controls don't affect the signal at all, it seems as if the signal is completely bypassing the pots. What do I have wrong that would be causing this? Thanks for any insight!

enter image description here

\$\endgroup\$
1
  • \$\begingroup\$ I fail to see how your battery powers anything and also, TL071 have a recommended minimum power range of +/- 5 volts. \$\endgroup\$
    – Andy aka
    Jul 15 '19 at 14:42
2
\$\begingroup\$

Normally a single supply Op Amp is biased on both input pins at Vcc/2 and not Gnd as you have done to Vin+.

This may pass residual signals but not function as a linear Op Amp.

\$\endgroup\$
3
  • 2
    \$\begingroup\$ The signal will pass through the feedback network straight to the output of the opamp. It won't be affected by the control settings. \$\endgroup\$ Jul 15 '19 at 14:28
  • 1
    \$\begingroup\$ @KevinWhite the DC feedback gain \$A\beta\$ of IC1 is 1, but the DC bias voltage applied to the \$V_{in_+}\$ non inverting input is the GND Voltage and brings the output down to the same level, collapsing the output dynamic range. As correctly noted by Sunnyskyguy, if you connect \$V_{in_+}\$ to a \$\frac{1}{2}V_+\$ level, the correct dynamic range is restored. \$\endgroup\$ Jul 15 '19 at 15:08
  • 2
    \$\begingroup\$ @DanieleTampieri - I agree. I was just describing the mechanism that the signal gets to the output when the opamp is non-functional due to incorrect biasing. \$\endgroup\$ Jul 15 '19 at 15:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.