Ordered an HFDY loop. I pretty much simply want the amp board, but anyway. ~$30 for an assembled LZ1AQ-based loop is decent IMO.
As noted earlier, the HFDY loop amp lacks a low-pass input filter, has no onboard voltage regulator, and has lower OIP2/OIP3 performance than more expensive LZ1AQ designs.
1. A 30MHz low-pass filter between the loop and amp is not difficult to implement, but I doubt it will be needed at my QTH. I have tested rather large antennas and cheap high-gain preamps without noticed FM overload here.
2. A voltage regular on the amp board is not really required if using a decent power supply. I can do that so whatever IMO.
3. The OIP2/OIP3 is still okay enough for my intended mostly HF purposes. At any rate the OIP3 as measured appears to be around 9dB better than the first-gen NE592-based MLA-30 amp board.
On a tangent related to the MLA-30, I ordered a couple of inexpensive NE592 preamp boards as a starting point for some further experimentation. Basically this in the through-hole version but without the bias tee components:
https://www.pcbway.com/project/shareproject/Antenna_Magnetic_loop_on_video_amplifier_NE592_DIP_version_10ff2fb5.htmlThey might prove useful enough for later projects after a little work on the input and output sides.