Hoppe’s Brain is full! Declaring a hiatus on new repairs and refurbishings.

Hi Everyone,

Hoppe’s Brain is thriving, but demand for my services has been overwhelming! My waiting list has grown to more than a year, so I’m sorry, but I must declare a temporary hiatus on accepting new clients for repairs and refurbishings.

I need concentrate on my existing customers. Thanks for understanding.

I still sell circuit boards and kits, and this area of Hoppe’s Brain will continue to expand. Look for my store to go online in the next few weeks. In the meantime, contact me with the form below and let me know what you want. (Power supply boards for GFA-535, 545 and GFA-555 amplifiers, GFA-565 input boards, etc.)

If you’ve emailed me and not heard back, I will get back to you within the next few weeks.

Thanks to my awesome customers for making Hoppe’s Brain a success!


A tour of a Hoppe’s Brain GFA-555 restoration

Hi everyone! One of my customers sent me a particularly nice GFA-555 MKI to be refurbished. It’s never been tampered with, and has very few scratches on the case… just beautiful. So I thought I would take lots of pictures along the way as I refurbish it, and show you the latest iteration of my GFA-555 rebuild process. This is the full monty upgrade package including the Hoppe’s Brain soft-start power supply board, with all sound quality and reliability improvements. $1025 in total.

Adcom GFA-555 Amp, being all amp-ey.

Continue reading A tour of a Hoppe’s Brain GFA-555 restoration

Introducing the Hoppe’s Brain Adcom GFA-555 soft-start power supply

Exciting news! Hoppe’s Brain power supply boards for the GFA-555 are here!


These boards feature a number of improvements over the stock arrangement with the old-style chassis-mount components:

  • Soft-start circuit reduces stress on components like switches and capacitors.
  • Reduced hum, buzz and noise from the amplifier’s speaker outputs.
  • Capacitance upgrade from 4×15,000uF to 4×27,000uF. Nearly double!
  • Earth-loop breaker with diode clamp safety shunt.
  • Amp is converted to a 3-wire, earth-grounded chassis appliance, for safety and better noise rejection.
  • Surge protection MOV
  • Snubber capacitors across AC side of bridge rectifiers
  • Compact layout. Overall wiring lengths reduced, fewer mechanical connections, and a much cleaner internal layout.

Continue reading Introducing the Hoppe’s Brain Adcom GFA-555 soft-start power supply

How I clean Adcom GFP-555 and GFP-565 record and playback selector switches

Hey folks, I hope this will be useful to anyone attempting to clean an ALPS sliding listen/record selector switch like those used in the Adcom GFP-555 and GFP-565. These are common in many brands of preamps and receivers.

Ribbon slider-switch inside GFP-555.

Continue reading How I clean Adcom GFP-555 and GFP-565 record and playback selector switches

Improving turn-around time: Narrowing focus, new lab

Hello everyone,

My sincerest apologies; My communications have been terribly slow, and my turn-around time for refurbished equipment is getting out of hand. I have customers waiting up to four months for their equipment, and that’s no good. I wouldn’t want to wait that long!

I never anticipated such a level of interest! Many thanks to all of my customers; it’s a pleasure to help you build your music systems, and I love hearing people’s comments after they get their gear back.

I like to say “YES!” to everyone’s projects, but I have taken on more work than I can possibly keep up with. I am buried in emails, and it’s getting hard to find time to work at the bench. Things are snow-balling on me.

It’s a good problem to have. It means I’m succeeding, but I won’t be for long if I don’t limit the scope of what I do.

Continue reading Improving turn-around time: Narrowing focus, new lab

Killing the buzz in the Adcom GFA-535. New power supply boards!

Adcom GFA-535 owners; Has it always bugged you, how the right channel of your amp buzzes through your speakers more than the left channel? Yeah, me too. The buzz is a buzz-kill… so I killed the buzz! With this thing I made.

GFA-535 I PS Board

Now, the GFA-535 is a legendary little amplifier, deserving plenty of buzz, but it’s too bad so much of it comes out the speakers. Oddly, the GFA-535’s bigger sibling—the GFA-545—using the exact same amplifier boards as the 535, is nearly silent as a stone. What’s going on?

Continue reading Killing the buzz in the Adcom GFA-535. New power supply boards!

ADCOM GFP-750 upgrade

The Adcom GFP-750 preamp was designed as a companion piece to the GFA-5802, with matching aesthetics. It’s a MOSFET based, single-ended Class-A preamp designed by Nelson Pass. Conceptually, it’s similar to the Pass Aleph P and the ‘Bride of Son of Zen’ DIY project.

NOTE: For visual comparison only. DO NOT STACK anything on top of a hot-running amplifier like the GFA-5802.

Continue reading ADCOM GFP-750 upgrade