Other Parts Discussed in Thread: OPA2134
Hello,
I have built a TL072 based amplifier for a piezo pick (i.e. a "contact microhpone") and I would like to improve it. Schematic and boards are here.
My design combines an OpAmp amplifier, with a JFET buffer to allow the preamplified microphone signal to be "recognized" by consumer electronics like mobile phones, as a viable audio input device. The OpAmp portion runs on a 12V battery, while the JFET buffer is powered by the ~3V provided by a mobile phone's "plug-in power" (usually used to power a headset's microhpone).
I'm looking to improve this design towards the following ends:
- Tone control: depending on the type of piezo, the tone (i.e. "color" or spectral contents) of the audio can vary quite a bit. I'd like to be able to control the tone of this preamp with a potentiometer.
- Optimal Gain: I'm using the potentiometer on R9 as my gain control; the gain of the OpAmp is defined by the ratio between R9 and R8. I'd like to know the optimal values to use for these resistors to have the highest fidelity
- Improved sound quality: I have tried this circuit with an OPA2134 as well as a TL072, which are pin compatible. I expected much better performance from the OPA2134, but did not perceive a difference. I'd like to know about other ICs to consider for this application.
- Improved battery life: my A27 batteries are lasting only about 2 hours. I'd like suggestions on how to improve the battery performance for this preamplifier.
Thank you!
Ali Momeni
