ELF/VLF Pre-Amp partial kit – $25
Being new to the group and ELF/VLF in general, I was impressed with the simplicity of Peter’s (VK2AN) ELF pre-amp circuit he posted in the vlf.io group. I contacted him and asked if I could make a partial kit available to the interested community. After many emails, he helped me to to understand the unique orientation and requirements of mounting the TI LMP7721 Femtoampere Precision OpAmp on a pcb.
This board is basically Peter’s posted circuit, with an 50/60Hz Twin “T” notch filter to filter out domestic supply interference, between the antenna, and his circuit that can be optimized for 60Hz or 50Hz, depending on your local supply frequency. The filter can be switched in or out if desired. The pre-amp can be used portable with the 9V battery or hard wired in a remote installation. The balanced audio output is via an RJ54 connector for a cat5 run to your sound card.
This is only offered as a partial kit that includes parts a normal experimenter/builder may not have. The PCB, LMP7721 OpAmp, 1G ohm resistor, neon bulb, 600:600 ohm transformer, and the SIP components are supplied. Most all the other components are common parts and may be already in your inventory, or readily available from your suppliers.
Click here for the assembly manual
