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.

Folks, I have been building lots of boards lately, and I now have stock of built-and-tested boards for every model except the GFA-555 MKII.
Get ’em here!

Adcom GFA-565 Replacement Circuit Board

Adcom GFA-555 MK1 Input Board

ADCOM GFA-555 MK1 Input Board for EARLY Rack-Mount Models

ADCOM GFA-555 MK1 VERTICAL Input Board

Adcom GFA-585 Replacement circuit boards. (Pair)

How’s this for procrastination? I’ve had these boards ready to sell since 2017, and have been using them in my own projects, but only now got them up in the store! Buy them here…

Earth-Loop Breaker Board

Continue reading New Product! Earth-Loop Breaker Boards

Real talk y’all. Hoppe’s Brain has been in business since 2016, yet I am constantly BROKE. I barely have enough money to keep parts in stock, and my partner has been paying more than their fair share of household expenses. I feel guilty when I spend money on fun things. I haven’t had a real vacation in 8 years. 🙁 It cannot go on like this. I am stressed out, working my ass off, and yet constantly struggling financially.

So what’s the problem? Profit margins on my products are good, and I’m working about 50-60 hours per week! It’s not because I’m not working hard!

I’ve realized it’s because I’m not getting paid for my time, doing tech support for customers, and teaching people electronics in the course of doing so.

I spend hours every day, answering tech support emails and taking phone calls, helping people troubleshoot their amplifiers for free. I really love helping people fix their stuff. It’s why I’m in business. But I can’t do it for free anymore.

Electronics is hard, amplifiers are complex, and there is so much that can go wrong with them. It takes years of training and practice to get proficient at fixing amplifiers. Most of my customers are hobbyists with real jobs, so they cannot be expected to be expert electronics technicians, and that’s great! It’s a fun hobby! But when people get stuck on their repairs, or the magic smoke escapes from their amplifier, and they’ve already spent lots of money with me already, I feel obligated to help them get it up and running. I really want them to succeed! Sometimes I worry that the customer’s problem might actually be something that’s my fault, or that maybe the board is bad, or maybe I got a bad part from a supplier… etc etc etc…

But you know what? It doesn’t even matter if it’s my fault, I still need to bill for my time. My products are superb, and I work super hard to make sure they are as flawless as humanly possible. But I am human, and I do make mistakes, and that risk is part of the price of doing business with me.

New policy: My products come with 30 minutes free tech support, and that includes writing emails, phone calls, and researching your issue. Time beyond 30 minutes is billed at $75/hr. If you anticipate needing help getting your amp running, I am happy to do that, but please consider my time as part of the price.

Thanks for reading, and for all the support I get, it’s much appreciated.

Chris

Parts shortages are stressing me out! And threatening my business. I’m worried that the Central Semiconductor CMXSTB400 is about to go extinct. Mouser is the only supplier, with 371 in stock and none on order.

The only other stabistor that I’m aware of, is the Nexperia BAS17, a single stabistor diode in SOT23.

Continue reading Parts shortages 🙁

Y’all, I’ve added a couple of new questions to the ADCOM FAQ, and made some random edits and clarifications…

Which sounds better, the MKI or MKII?

Where were Adcom amps made? Is there any difference in quality?

The Problem:

You want to replace the binding posts in your amplifier, but the holes in the chassis are too large for most binding posts on the market, which are designed to fit chassis cut-outs of 10mm or 11.5mm in diameter.

The Solution:

Hoppe’s Brain Binding Post Adapter Plates.

Two fiberglass plates sandwich the sheet metal, and the binding posts fit into the plates, which are firmly attached with four M3 screws and locknuts. Simple, secure, and easy to install and service.

Get them here:

The board header connectors and cables inside GFA-585’s are often corroded, from leaked capacitor spittle and time. These types of “JST connectors” are meant to be machine-crimped, but they can be soldered manually, but that’s a real pain.

So I am offering a complete set of new cables and board headers for $40. They’ll be up in the store soon!

Cables for GFA-565 and GFA-555 MKII continue to be available.