Wondering if anyone can advise on this tube triode (12ax7) preamp stage followed by an Op Amp buffer stage to correct the inverted signal. I wired it up and did not work. Before tho, I wired it with 22K resistors instead of 220K. Perhaps signal was overloading OpAmp? Also, should the impedance output from the OpAmp be essentially the same as if it were from the triode, just inverted?
Triode preamp with TL072 phase inverter buffer
bufferoperational-amplifier
Related Topic
- Electronic – Bipolar Op Amp w/ Near Zero Offset
- Rail to rail OpAmp Parameters for signal conditioning
- Electronic – OP AMPs : ADC Buffer on voltage divider plus protection
- Electronic – high output impedance sensor with voltage output
- Electrical – Signal buffer with op-amp clamping and voltage bias
- Electrical – High impedance opamp attenuator
Best Answer
Middle 1 Meg Ohm resistor is not needed. Remove the 5000 pF capacitor from U1b (-) node.
You will have less gain than expected because the 220K input impedance of the op-amp stage is loading the output of the tube. But that's not enough to stop it from working.
What voltage are you running the tube's filament at?