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

So I’ve been sitting on this new design for a GFA-565 power supply for two years, because I haven’t found the time to test and validate the design before I start offering them for sale. I needed to install it in an actual amplifier and test its performance. Recently I found the time to build myself a GFA-565!

One of the key features of this new power supply, is the relocation of the bridge rectifier to the tops of the capacitors, which eliminates about 20 inches of 14ga hookup wire that normally runs from the bridge rectifier mounted on the floor on the left side of the amp, to the capacitors on the right side. In my design, the bridge rectifier is made up of four discrete diodes in TO-220 packages, mounted to a circuit board on top of the capacitors.

My design goal is that the heat dissipation for the bridge rectifier needs at least as good as—or better than—the OEM arrangement, with the bridge rectifier mounted to a heatsink on the floor of the chassis.

As I’m about to find out, this heatsink arrangement isn’t enough.

Continue reading Heatsink FAIL delays release of my new power supply for the GFA-565. :^/

It been nearly 5 years(!) since I posted my original ‘Tour of a Hoppe’s Brain GFA-555 Restoration”

A lot has changed since then. That restoration didn’t benefit from a new Hoppe’s Brain BFA-555 input board, or a binding post kit, and it uses an earlier version of my soft-start for the GFA-555. (Which is still a good power supply, but my new Smart Soft-Start BFA-555 power supply is better.)

So I’ve started taking on new refurb customers, at a much slower pace, and for a lot more money. 😸 I realized, like many small business owners, I have been under-charging for my work. The following is what you get when you drop some coin with me.

Continue reading Another tour of a Hoppe’s Brain Adcom GFA-555 restoration (5 years later with better technology.)

This board fits any single SO08 op-amp and a TI BUF634A buffer IC into a single DIP-8 socket!

Useful wherever increased current drive and immunity to capacitive load is desired. (Headphone amplifiers, line drivers, active filters, equalizers, etc.)

Buy them here.

The TI BUF634A adds a fast and powerful output stage to any op-amp. It is inserted into the feedback loop, essentially becoming a part of the op-amp itself.

Here’s one installed in a phono preamp I built for a friend. This particular design benefited greatly from the BUF634A, as the output drives a 464 ohm load on its feedback loop, which is a heavy load for most op-amps, but a breeze for the BUF634A.