Preamp PCB Layout
The preamp is contained on one PCB, measuring 220mm x 123mm. There are approximately 126 parts mounted on the board. It cost me just over $170.00 to buy the parts, not counting the DOAs, for 2 boards. It would cost under $100 for the parts for a single board. The power supply is not included in this cost. It turns out to cost $62 for all of the parts for two power supplies, and about $40 for one.
Your overall cost will depend on your source for each part, of course. I left the screw terminal blocks off because they are a few dollars for all of them on AliExpress. They are 5.00mm on center.
Power Supply PCB Layout
The power supply is a simple linear regulator x 5 using LM317 and LM337 regulators. The 5V, ±15 and ±24 are adjustable. The outputs are:
- +5V + 60Hz pulse for another project
- +12V unregulated, for the back panel input relay board
- ±15V @ 0.5A for the OPA227 op amps
- ±24V @ 1A for the 990C+ op amps
As long as the unit is powered up there will be one tiny 5V relay energized in the back panel input relay board. The 990 op amps can source 250mA into 75Ω, but won’t ever see that in this application. The current requirement the OPA227’s is a few mA each.