Hello,
I'm working on project to produced Pulsed ElectroMagnetic Fields (PEMF) at LOW frequencies (0-100Hz) using various wave functions. (sine, square, triangle, sawtooth)
The whole design is very similar to what an audio amplifier and speaker setup would be since speakers are essentially coils with low resistance/impedance.
The input signal would ideally come from a 3.5mm headphone jack or even better Bluetooth as I see some small pre built class D amplifiers include such.
I've considered using OpAmps, transistors, Mosfets but seems pre-built class D amps gets me near 95% there so why build from scratch.
Any off the shelf class D amp would work except for one problem. The low cut of frequency of all pre-build amplifiers is often between 14Hz and 20Hz and understandably so since they are made for audible sounds.
Ideally, I need to account for super low frequencies, 1Hz or even lower, 0.5Hz, 0.1Hz etc.
Power between 10 watts and 50 watts.
Though I can solder and have build projects before, Ideally, the less building the better.
So, my question is this.
Is there any off the shelf audio amplifiers that would also amplify signals even as low as 0-20Hz ? Probably what would be considered a bad quality/cheap amp?
If not, are there any that could be easily modified by changing any input filers (RL) that would allow lower frequency signals to pass into the amplifier?
Something like this would be great if could amplify 0-20Hz: https://www.amazon.com/Bluetooth-Receiver-Amplifier-Audio-Fosi/dp/B087FTV362/
Looking at the specs of the chip (TPA3116D2) it contains ...
https://www.ti.com/product/TPA3116D2#tech-docs
...it is not clear to me if a lower input frequency can be permitted by removing or changing external components
Would not be easy on this pre-built device since it does not use normal regular size capacitors and resistors that would be much easier to work with.
I'm open to suggestions. I may be going in a completely wrong direction. It seems there should be a simple answer but my project is not so common.
Requirements again:
Amplify low power signal from 3.5mm jack or phones bluetooth.
input signal 0-20Hz made up of various common waveforms
Total Power 10-50watts
Drive copper coils/speakers 4-8ohms
Adjustable output power/volume knob
pre-built or minimum modifications to a pre-built amp. Worse case will build it
Fast and Easy is more important than cost at this point.
Thanks again for any suggestions or feedback. I'm open to anything that may take me in an unforeseen direction.
Ben