Hoppe's Brain

Hey internet, I just finished refurbishing this GFA-555, and the customer opted to go without the BFA-555 Smart Soft-Start Power Supply, so if you’re wondering what you get without this option, here it is! I do install some Capacitor Hats to replace the crusty originals. The original power supply capacitors were replaced with Kemet ALS30, 22,000uF, which is about as big as you can go without a soft-start. (Or the switch will spark too much and the fuse may blow due to the in-rush current.)

Invoice on this one was $1210.

Dust is attracted to high static voltage, dramatically illustrated here on the underside of an Adcom GFA-555. These dusty traces are at only 80V potential, but that’s enough to make them dustier than surrounding traces at lower voltages.

For those of you who prefer a more original looking GFA-565 board, I still sell this older version, the BFA-565. It works great. I prefer the new version, the EBFA-565; It has many subtle improvements, is easier to build, easier to install, and even shows a measurable improvement in performance.

But the original board is still available if you want it! Here.

Every circuit board I sell need to be thoroughly tested, and measurements taken that should agree with expected values. Tests are chosen to show up any errors I might have made in the board’s assembly.

• Gain. I use 0.1% tolerance resistors in key parts of the circuit, so gain should match within 0.01db from one board to another.
• DC operating points, such as the drive voltage to the output sections, DC offset, DC servo output, and bias voltages
• Distortion; it should match measurements from other boards, all the way up to full-scale output.
• Current running through various branches of the circuit.
• Functionality of indicator LEDs

Here’s how I build my test jigs.

Long story short: Printed circuit board+Pogo pins=Test jig.

Continue reading How to build a Test Jig, or Test Fixture, for your Printed Circuit Boards

Good news! I have tested and validated the performance of the new heat sinks for the BFA-565 power supply board. They work great, and the boards will be ready for purchase later this week.

Continue reading Heatsink WIN! New BFA-565 power boards are go. 👍

Check out these serial number tags! So cool. They’re made of 1mm thick FR4 PCB material, with the text in ENIG gold finish. I use an engraver pen to fill in the date for the serial number. Held in place with a little JB Weld epoxy.

Big news! I have completely re-designed circuit boards for the Adcom GFA-565. Based on customer feedback, I’ve made many improvements. These new boards are easier to install, harder to screw up, and they even perform a little better!

Buy them here. Hoppe’s Brain EBFA-565.

Continue reading Introducing the EBFA-565; the Even Better F–cking Amplifier (New version Adcom GFA-565 Circuit Boards)

EBFA-565 Assembly and installation guide