One of my first Hoppe’s Brain customers sent me this beautiful old preamp to work on. Eight years ago I had refurbished for him, a pair of Adcom GFA-565’s to drive a pair of power-hungry Eminent Technology EFT-8 planar speakers. He loved my work, and sent me this preamp to restore.
Continue reading Spectral Audio DMC-10 Restoration (Send me more gear like this please!)
UPDATE: 2024.03.03 They’re now available in the Hoppe’s Brain Shop!
Here’s a (literally) cool solution to replace those MT-200 output transistors in your vintage amp or receiver! These adapters equal the excellent thermal performance of MT-200 devices, using commonly available TO-3P or TO-247 transistors.
The entire adapter is solid copper all the way through; there is no insulating layer. The TO-3P transistor is simply surface-mount soldered to the adapter, using solder-paste and hot-air. The backplate (collector) is connected to the copper body of the adapter.
Continue reading New product teaser; MT-200 to TO-3P output transistor adapters!
I’ve been making new, more reliable test jigs for all the most popular boards I sell. This jig for the BFA-555 MK1 features a replica of the entire output section of a GFA-555, but with only one pair of output transistors. Obviously, you can’t run much power through this, but it’s all I need to prove the board works.
Pogo-pins meet target pads on the underside of the board under test.
An old 1/4″ jack, a little dremelling, shrink wrap and zip ties…
I’ll just put this here. My DBX 166A compressor had terribly corroded 1/4″ phone jacks, and I found these exact replacements with gold-plated contacts. Neutrik part number NRJ6HF-1-AU (Gold plated) or NRJ6HF (Silver plated). These jacks are used in many other DBX products.
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, which includes new Kemet power supply capacitors. Without the capacitors this is a $930 job.
Dust is attracted to electric fields, and sticks to a board in a way that reveals the shape of the electric field in one plane. Dramatically illustrated here on the underside of an Adcom GFA-555. These dusty traces are at only 83V potential, but that’s enough to make them dustier than surrounding traces at lower voltages. Check out how there is a bunch of dust between the grounded mounting bracket and the adjacent trace at 83VDC.
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.
Printed circuit board+Pogo pins=Test jig.
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.
Here’s how I build my test jigs.
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. 👍
