OPA657 Setup

NOTE: The process outlined in this page was intended to be informational with regard to capturing "Laserdisc" RF. If you are intending to only capture VHS RF, please see the "bigpotAD8367" guide instead.

CARD: White PCIe CX23883 card (pic to identify: https://github.com/tandersn/cxadc-hw-mod/blob/main/X_Pictures/cxcard4ad8367/stockCXwhite.jpg)
AMP: OPA657 with manual gain adjusted (pic to identify: https://raw.githubusercontent.com/tandersn/cxadc-hw-mod/main/X_Pictures/opa657/th-532925870.jpg)
FILTER: Mini Circuits SXLP-13+ (or BLP-10.7+)
CRYSTAL: 40MHz - ABRACON ABLS2-40.000MHZ-D4YF-T 18pF 30ppm HC-49/US
POWER: The OPA657 needs a split power supply. There are few options, and the easy option is a bit more clumsy, and the more robust option is more work. I recommend the more robust option.
- Two 3x AAA battery holder with switch: https://raw.githubusercontent.com/tandersn/cxadc-hw-mod/main/X_Pictures/opa657/3aa.jpg (get a 4xAA if you want to use rechargeable batteries, as they are lower voltage)
- One 6x AAA battery holder: https://raw.githubusercontent.com/tandersn/cxadc-hw-mod/main/X_Pictures/opa657/6aa.jpg (get an 8xAA if you want to use rechargeable batteries, as they are lower voltage)
MISC: resistors, capacitors, small project box, SMA/BNC/RCA adapters and connectors, small zip ties, double sided foam tape

With this setup, and the mods detailed in the pages to the right, i've achieved very good results. PLEASE READ through all the pages before starting, as some of the optional mods negate some of the steps of other mods. For example: Doing the direct wire mod negates the need to remove / replace SMD components on the cx card.

The pros of this setup, and the reasons i put it first are:

Highly tunable
Works better in 50ohm standard impedance values

The cons are:

Complex setup requiring split power source
Requires special procedure and capture script cxlvlcavdd for capturing CAV disks https://github.com/happycube/cxadc-linux3/blob/master/utils/README.md
More sensitive to battery charge state than AD8367
Not enough empty component places on the board, so we have to create one extra.

As mentioned earlier, using OPA657 with CAV discs requires using the cxlvlcavdd script in the cxadc utils folder: readout Above is most of a capture of ggv1069 test disc, using the cxlvlcavdd script that turns down the gain as the capture is being done.